%1 http://coloradoencyclopedia.org/ en Precious Metal Mining in Colorado http://coloradoencyclopedia.org/article/precious-metal-mining-colorado <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--title--encyclopedia-article.html.twig x field--node--title.html.twig * field--node--encyclopedia-article.html.twig * field--title.html.twig * field--string.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <span class="field field--name-title field--type-string field--label-hidden">Precious Metal Mining in Colorado</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: x field--node--field-article-image--encyclopedia-article.html.twig * field--node--field-article-image.html.twig * field--node--encyclopedia-article.html.twig * field--field-article-image.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--field-article-image--encyclopedia-article.html.twig' --> <div id="carouselEncyclopediaArticle" class="carousel slide" data-bs-ride="true"> <div class="carousel-inner"> <div class="carousel-item active"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'node' --> <!-- FILE NAME SUGGESTIONS: * node--3767--article-detail-image.html.twig * node--3767.html.twig x node--image--article-detail-image.html.twig * node--image.html.twig * node--article-detail-image.html.twig * node.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/content/node--image--article-detail-image.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-encyclopedia-image--image.html.twig * field--node--field-encyclopedia-image.html.twig * field--node--image.html.twig * field--field-encyclopedia-image.html.twig * field--image.html.twig x field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field.html.twig' --> <div class="field field--name-field-encyclopedia-image field--type-image field--label-hidden field__item"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image_formatter' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-formatter.html.twig' --> <a href="/image/gold-taken-colorado-mine"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image_style' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-style.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image.html.twig' --> <img loading="lazy" src="/sites/default/files/styles/wide/public/Gold_%28Dixie_Mine%2C_Idaho_Springs%2C_Colorado%2C_USA%29_3_%2817030135106%29_0.jpg?itok=RpPwBrd-" width="1090" height="757" alt="" typeof="foaf:Image" class="image-style-wide" /> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image.html.twig' --> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-style.html.twig' --> </a> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-formatter.html.twig' --> </div> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field.html.twig' --> <div class="carousel-caption d-none d-md-block"> <h5><a href="/image/gold-taken-colorado-mine" rel="bookmark"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--title--image.html.twig x field--node--title.html.twig * field--node--image.html.twig * field--title.html.twig * field--string.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <span class="field field--name-title field--type-string field--label-hidden">Gold Taken from Colorado Mine</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> </a></h5> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--body--image.html.twig * field--node--body.html.twig * field--node--image.html.twig * field--body.html.twig x field--text-with-summary.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--text-with-summary.html.twig' --> <div class="clearfix text-formatted field field--name-body field--type-text-with-summary field--label-hidden field__item"><p>During the raising of the <a href="/article/rocky-mountains"><strong>Rocky Mountains</strong></a> millions of years ago, superheated fluids rose from deep within the Earth and pushed minerals such as gold and silver up through the Earth's crust. Erosion brought pieces of gold downstream in creeks (placer gold), while the deeper deposits (lode gold) could only be recovered by skilled labor and technology.</p> </div> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--text-with-summary.html.twig' --> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/content/node--image--article-detail-image.html.twig' --> </div> <div class="carousel-item"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'node' --> <!-- FILE NAME SUGGESTIONS: * node--3768--article-detail-image.html.twig * node--3768.html.twig x node--image--article-detail-image.html.twig * node--image.html.twig * node--article-detail-image.html.twig * node.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/content/node--image--article-detail-image.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-encyclopedia-image--image.html.twig * field--node--field-encyclopedia-image.html.twig * field--node--image.html.twig * field--field-encyclopedia-image.html.twig * field--image.html.twig x field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field.html.twig' --> <div class="field field--name-field-encyclopedia-image field--type-image field--label-hidden field__item"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image_formatter' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-formatter.html.twig' --> <a href="/image/argo-tunnel"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image_style' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-style.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image.html.twig' --> <img loading="lazy" src="/sites/default/files/styles/wide/public/6210103088_252254fdb0_k_0.jpg?itok=DjskRzJC" width="1090" height="726" alt="" typeof="foaf:Image" class="image-style-wide" /> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image.html.twig' --> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-style.html.twig' --> </a> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-formatter.html.twig' --> </div> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field.html.twig' --> <div class="carousel-caption d-none d-md-block"> <h5><a href="/image/argo-tunnel" rel="bookmark"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--title--image.html.twig x field--node--title.html.twig * field--node--image.html.twig * field--title.html.twig * field--string.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <span class="field field--name-title field--type-string field--label-hidden">Argo Tunnel</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> </a></h5> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--body--image.html.twig * field--node--body.html.twig * field--node--image.html.twig * field--body.html.twig x field--text-with-summary.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--text-with-summary.html.twig' --> <div class="clearfix text-formatted field field--name-body field--type-text-with-summary field--label-hidden field__item"><p>The Argo Tunnel was part of the <a href="https://coloradoencyclopedia.org/article/precious-metal-mining-colorado"><strong>precious metal minin</strong></a>g operations in <a href="/article/gilpin-county"><strong>Gilpin</strong></a> and <a href="/article/clear-creek-county"><strong>Clear Creek County</strong></a> during the late nineteenth century. At more than four miles long, it connected a host of gold mines between <a href="https://coloradoencyclopedia.org/article/central-city%E2%80%93black-hawk-historic-district"><strong>Central City</strong></a> and <strong>Idaho Springs</strong> before it was shuttered following an accident in 1943.</p> </div> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--text-with-summary.html.twig' --> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/content/node--image--article-detail-image.html.twig' --> </div> </div> <button class="carousel-control-prev" type="button" data-bs-target="#carouselEncyclopediaArticle" data-bs-slide="prev"> <span class="carousel-control-prev-icon" aria-hidden="true"></span> <span class="visually-hidden">Previous</span> </button> <button class="carousel-control-next" type="button" data-bs-target="#carouselEncyclopediaArticle" data-bs-slide="next"> <span class="carousel-control-next-icon" aria-hidden="true"></span> <span class="visually-hidden">Next</span> </button> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--field-article-image--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--uid--encyclopedia-article.html.twig x field--node--uid.html.twig * field--node--encyclopedia-article.html.twig * field--uid.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--uid.html.twig' --> <span class="field field--name-uid field--type-entity-reference field--label-hidden"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'username' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/user/username.html.twig' --> <span lang="" about="/users/yongli" typeof="schema:Person" property="schema:name" datatype="">yongli</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/user/username.html.twig' --> </span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--uid.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--created--encyclopedia-article.html.twig x field--node--created.html.twig * field--node--encyclopedia-article.html.twig * field--created.html.twig * field--created.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--created.html.twig' --> <span class="field field--name-created field--type-created field--label-hidden"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'time' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/time.html.twig' --> <time datetime="2022-08-09T11:55:06-06:00" title="Tuesday, August 9, 2022 - 11:55" class="datetime">Tue, 08/09/2022 - 11:55</time> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/time.html.twig' --> </span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--created.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'addtoany_standard' --> <!-- FILE NAME SUGGESTIONS: * addtoany-standard--node--encyclopedia-article.html.twig * addtoany-standard--node.html.twig x addtoany-standard.html.twig --> <!-- BEGIN OUTPUT from 'modules/contrib/addtoany/templates/addtoany-standard.html.twig' --> <span class="a2a_kit a2a_kit_size_32 addtoany_list" data-a2a-url="http://coloradoencyclopedia.org/article/precious-metal-mining-colorado" data-a2a-title="Precious Metal Mining in Colorado"><a class="a2a_dd addtoany_share" href="https://www.addtoany.com/share#url=http%3A%2F%2Fcoloradoencyclopedia.org%2Farticle%2Fprecious-metal-mining-colorado&amp;title=Precious%20Metal%20Mining%20in%20Colorado"></a><a class="a2a_button_facebook"></a><a class="a2a_button_twitter"></a><a class="a2a_button_email"></a></span> <!-- END OUTPUT from 'modules/contrib/addtoany/templates/addtoany-standard.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--body--encyclopedia-article.html.twig * field--node--body.html.twig x field--node--encyclopedia-article.html.twig * field--body.html.twig * field--text-with-summary.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-body field--type-text-with-summary field--label-hidden field__item" id="id-body"><p>From the 1850s to the 1920s, gold and silver mining drove Colorado’s economy, making it into an urbanized, industrial state. The rapid development of Colorado’s mineral resources had political, social, and environmental consequences. The mining of gold and silver in Colorado began in earnest during the <a href="http://www.coloradoencyclopedia.org/article/colorado-gold-rush"><strong>Colorado Gold Rush</strong></a> of 1858–59. The state’s first miners used metal pans to sift gold nuggets out of riverbeds. Prospecting these streams quickly outlined a mineral belt stretching diagonally across the state from <a href="http://www.coloradoencyclopedia.org/article/boulder-county"><strong>Boulder County</strong></a> to the <a href="http://www.coloradoencyclopedia.org/article/san-juan-mountains"><strong>San Juan Mountains</strong></a>. Colorado’s principal towns and mines were developed within this belt. Industrial mining followed, allowing for deeper extraction of gold and silver.</p>&#13; &#13; <p>Gold and silver mining spurred many events in Colorado history, including the removal of <a href="https://coloradoencyclopedia.org/person/native-americans"><strong>Indigenous people</strong></a>, the development of commercial agriculture, the organization of the <a href="http://www.coloradoencyclopedia.org/article/colorado-territory"><strong>territory</strong></a> and state of Colorado, the <strong>Civil War</strong> in the West, the development of <strong>railroads,</strong> and heavy industry such as <a href="https://coloradoencyclopedia.org/article/coal-mining-colorado"><strong>coal mining</strong></a>, precious- and base-metal <strong>smelting</strong>, and<strong> steel production</strong>. Most of the state’s influential political figures from the late nineteenth through the early twentieth centuries had connections to the metal industry. That industry attracted immigrants, ideas, and technology from all over the world. Mining and smelting also led to the development of unions, strikes, and labor conflicts in Colorado.</p>&#13; &#13; <p>Although it no longer underwrites the state economy, precious metal mining continues in Colorado today, the ongoing legacy of discoveries made more than 150 years ago.</p>&#13; &#13; <h2>Geology of Precious Metals</h2>&#13; &#13; <p>Colorado’s precious metals were embedded into the rocks of the northeastern <a href="http://www.coloradoencyclopedia.org/article/rocky-mountains"><strong>Rocky Mountains</strong></a> tens of millions of years ago. Superheated fluids transported dissolved minerals into fractures in pre-Cambrian and metamorphic rocks and into soluble Paleozoic limestone. As the solutions cooled, free metals and metallic compounds were deposited in the rock. Gold is generally found throughout veins of quartz-rich igneous rocks called “pegmatites” or compounded with another element called tellurium into “gold telluride.”</p>&#13; &#13; <p>Silver, meanwhile, is rarely found on its own. It is usually associated with lead, zinc, iron, and <strong>other metals,</strong> as well as non-metallic sulfur, carbonate, and chloride in minerals such as galena, cerussite, and sphalerite. These minerals formed the heavy, dark gray silver-lead ore found in <a href="http://www.coloradoencyclopedia.org/article/leadville"><strong>Leadville</strong></a> during the 1870s. And as the iron sulfide (also called pyrite or “fool’s gold”) was exposed to air, it was altered to form weak sulfuric acid that leaks out of mines and into local water sources, a phenomenon known as <strong>acid mine drainage</strong>.</p>&#13; &#13; <p>In the northeastern Colorado mineral belt, the mountains were uplifted at the end of the Cretaceous Period (65–70 million years ago). Fast-flowing water and glacial ice eroded these rocks and deposited the metals in the gravel and sand of stream channels, sand bars, and terraces. These streams were the first locations where gold was found in Colorado.</p>&#13; &#13; <p>The southwestern portion of the mineral belt was formed very differently. Around 25–35 million years ago, a long episode of volcanic eruptions deposited thick lava flows over the entire region. Some of these were super-sized, explosive volcanoes that created calderas similar to the Yellowstone caldera, only smaller. Superheated fluids containing dissolved metals, similar to the geysers in Yellowstone, flowed into fractures in these volcanic rocks and precipitated the metals as they cooled. These calderas—including the Silverton, Lake City, Creede, Bonanza, La Garita, and others—are now the locations of the principal San Juan mining districts.</p>&#13; &#13; <h2>Types of Mining</h2>&#13; &#13; <p><em>Placer Mining</em></p>&#13; &#13; <p>Panning gold from stream and terrace gravels is called <em>placer </em>mining, derived from the Spanish word <em>placer</em> or “pleasure”—the gold is available at one’s pleasure. Between 1858 and 1867, Colorado placer miners took out more than $14 million in gold (when gold was valued at about $20 per troy ounce) from creeks and streambeds. The early Colorado prospectors needed only a large pan that looked like a pie pan, a pick, and a shovel to pan for gold. Being denser than the sand around it, the gold settled to the bottom of the pan as the water and lighter sand swirled away.</p>&#13; &#13; <p>A strong magnet could then separate heavy black iron (magnetite) that would settle to the pan's bottom. A problem in some parts of Colorado was the presence of another heavy black mineral that was non-magnetic. During the early gold rush, this mineral was assayed as a lead compound, which was worthless to gold miners. Only later would it be found to contain silver as well as lead, zinc, and other metals.</p>&#13; &#13; <p>To process more gold-bearing sand than an individual with a pan, miners began working in teams using rockers, a cradle-like wooden box, and sluices—long, high-sided wooden flumes with numerous cross-pieces nailed to the bottom. Both techniques emulated the natural stream-sorting of the denser gold nuggets, flakes, and dust while carrying off the gravel and sand. Because a considerable flow of water was needed to separate the gold, this technology was little used in areas with seasonal stream flows.</p>&#13; &#13; <p><em>Hydraulic Mining</em></p>&#13; &#13; <p>When placer deposits ran out, miners in places such as <a href="http://www.coloradoencyclopedia.org/article/park-county"><strong>South Park</strong></a> and <a href="https://coloradoencyclopedia.org/article/breckenridge-historic-district"><strong>Breckenridge</strong></a> turned to hydraulic mining, in which highly pressurized water was used to blast thick terrace gravel away from hillsides, sending the metal-containing debris down into a series of sluices. However, the relative lack of water and hose materials, as well as the fact that many gulches had already been placer-mined to exhaustion, meant that hydraulic mining did not become as prevalent in Colorado as it had in California.</p>&#13; &#13; <p><em>Hard-Rock Mining</em></p>&#13; &#13; <p>Instead of hydraulic mining, most of Colorado’s gold and silver were taken out by mining the bedrock. Miners started using this method in the early 1860s. Lode or hard-rock mining required digging shafts and tunnels into the mountains, following the veins downward from the surface. Recoverable gold and silver in the lodes is called <em>ore</em>.</p>&#13; &#13; <p>At first, hard-rock miners used hand drills, sharpened pieces of steel like long chisels, that were hit with hammers to drill holes for black powder. The explosive would blow apart the ore-bearing rock, allowing the ore to be shoveled into ore cars for the trip to the surface. By the 1890s, when the <a href="http://www.coloradoencyclopedia.org/article/cripple-creek"><strong>Cripple Creek</strong></a> gold rush and silver booms in <a href="http://www.coloradoencyclopedia.org/article/aspen"><strong>Aspen</strong></a> and <strong><a href="https://coloradoencyclopedia.org/article/creede">Creede</a> </strong>were in full swing, hand drills began to be replaced by steam-powered or compressed-air drills.</p>&#13; &#13; <h2>Processing Precious Metals</h2>&#13; &#13; <p>In the early days of the Colorado Gold Rush, placer miners borrowed the Spanish process of using mercury to extract gold; the two heavy metals were bound together in an amalgam and would sink to the bottom of the sluice. The amalgam was then heated in a retort until the mercury vaporized, leaving the gold and retorted mercury to be collected.</p>&#13; &#13; <p>In the 1860s, before successful smelting in Colorado, ore was taken from a mine to a stamp mill, where it was crushed into sand and then washed over copper plates embedded with mercury, or simply into sluice boxes to recover the gold. The use of mercury posed a threat to miners, mill workers, and local wildlife, as documented by the gold seeker-turned-naturalist <a href="https://coloradoencyclopedia.org/article/edwin-carter"><strong>Edwin Carter</strong></a>.</p>&#13; &#13; <p>Early stamp milling was relatively inefficient, with as little as 25 percent of the gold content recovered. The inefficiency came because milling is only a physical separation process and does not break the chemical bonds between the rock and gold. As mines became deeper, lower-grade ore and ore laden with sulfides made profitable milling difficult. The result was the first “bust” in Colorado’s gold “boom.”</p>&#13; &#13; <h2>Advent of Smelting</h2>&#13; &#13; <p>In the late 1860s, entrepreneurial chemistry professor <a href="https://coloradoencyclopedia.org/article/nathaniel-p-hill"><strong>Nathaniel P. Hill</strong></a> applied a process he learned in Wales to build the state’s first successful smelter in <a href="https://coloradoencyclopedia.org/article/central-city%E2%80%93black-hawk-historic-district"><strong>Black Hawk</strong></a>. Smelters use heat to melt milled ore and chemically separate the precious metals. The advent of smelting not only revived the struggling mining industry in Colorado but also launched the potential extraction of silver from complex ores.</p>&#13; &#13; <p>Smelting also galvanized the <a href="file:///C:/Users/yongli/Downloads/coloradoencyclopedia.org/article/coal-mining-colorado"><strong>coal industry</strong></a>, as large amounts of coke—an industrial fuel derived from coal—were needed to fuel the smelters. By 1890 Leadville had fourteen smelters, <a href="http://www.coloradoencyclopedia.org/article/pueblo"><strong>Pueblo</strong></a> and Denver had three, and <a href="http://www.coloradoencyclopedia.org/article/golden"><strong>Golden</strong></a>, <a href="https://coloradoencyclopedia.org/article/salida"><strong>Salida</strong></a>, Aspen, and <strong>Durango</strong> each had one.</p>&#13; &#13; <p>A new gold-extraction process gained traction in Colorado during the Cripple Creek gold boom of the 1890s. Using cyanide to separate gold was, as mining historian Jay Fell writes, “far more efficient than stamp milling and far less expensive than smelting.” Like earlier stamp milling, the process involved crushing the gold ore into sand, but instead of running it over copper plates or through sluices, the cyanide mills sent the sand into vats of a cyanide solution which dissolved gold for extraction.</p>&#13; &#13; <p>Like smelting, cyanide milling was developed overseas; it was used extensively in South Africa during the 1880s before being implemented in Colorado mining operations at <a href="http://www.coloradoencyclopedia.org/article/crestone"><strong>Crestone</strong></a> and Cripple Creek. Despite the success of cyanide in gold processing, silver-lead-zinc ores still had to be smelted. Many Colorado silver-lead-zinc smelters operated until the 1920s, and one each in Denver and Leadville operated until the 1960s.</p>&#13; &#13; <h2>Timeline of Precious Metal Mining in Colorado</h2>&#13; &#13; <p><em>Early History</em></p>&#13; &#13; <p>The 1849 California Gold Rush set off the search for precious metals across the American West. On their way to California, various groups traveling across the Rockies began finding small amounts of gold in <strong>Cherry Creek</strong> and other streams near present-day Denver. These early findings attracted little attention after the 1851 <a href="https://coloradoencyclopedia.org/article/treaty-fort-laramie"><strong>Treaty of Fort Laramie</strong></a> made the area more accessible to non-Natives and an economic depression in 1857 led many eastern Americans to seek their fortunes in the West. In 1858 the party of <strong>William Green Russell</strong>, prospectors with experience from gold rushes in Georgia and California, made a minor gold discovery in Cherry Creek.</p>&#13; &#13; <p>The ensuing Colorado Gold Rush saw thousands of people cross the <a href="https://coloradoencyclopedia.org/article/colorado%E2%80%99s-great-plains"><strong>Great Plains</strong></a> to newly established towns such as <a href="http://www.coloradoencyclopedia.org/article/denver"><strong>Denver</strong></a>, <a href="http://www.coloradoencyclopedia.org/article/boulder"><strong>Boulder</strong></a>, Cañon City, and Golden; by 1860, the non-Native population of Colorado—which was then still controlled mainly by Indigenous people and officially part of western Kansas Territory—numbered over 34,000. The following year, with the Civil War looming, Congress organized Colorado Territory in part to safeguard the gold-producing region from the emerging Confederacy.</p>&#13; &#13; <p>Colorado’s population swiftly declined in the early 1860s, as many of the most popular gold streams were panned out and hard rock mining began. People left the area to join the Union or Confederate armies and to seek their fortunes in the Idaho and Montana gold rushes that began in 1862.</p>&#13; &#13; <p><em>Spread Across the Rockies</em></p>&#13; &#13; <p>In the mid-to-late 1860s, the violent removal of the <strong>Arapaho</strong> and <strong>Cheyenne</strong>, as well as treaties with the <a href="http://www.coloradoencyclopedia.org/search/google/ute"><strong>Ute</strong></a> people of the Rocky Mountains and the importing of stamp milling and smelting, revived Colorado’s gold-mining industry. This was followed in the 1870s by the development of railroads in the mining districts and discoveries of gold and silver in the San Juan Mountains, the <a href="http://www.coloradoencyclopedia.org/article/gunnison-county"><strong>Gunnison Valley</strong></a>, and Leadville. The forced removal of much of Colorado’s Ute population in 1881 made industrial mining possible in places such as Aspen (silver) and the San Juan Mountain towns of <strong>Ouray</strong>, <a href="https://coloradoencyclopedia.org/article/silverton-0"><strong>Silverton</strong></a>, and <a href="http://www.coloradoencyclopedia.org/article/telluride"><strong>Telluride</strong></a> (gold and silver).</p>&#13; &#13; <p><em>Silver’s Rise and Fall</em></p>&#13; &#13; <p>The fates of Colorado’s gold and silver mining industries were always bound to national events. Beginning in the late 1850s, during the Colorado Gold Rush, the rapid development of the Comstock Lode, a massive silver deposit in Nevada, sent the price of silver tumbling. The price drop continued when Colorado’s silver industry came alive in Leadville in the late 1870s, prompting those invested in western silver to lobby Congress for support. The Bland-Allison Act, passed in 1878, compelled the government to purchase a set amount of silver each year and was a boon for Colorado mines.</p>&#13; &#13; <p>Later, the Sherman Silver Purchase Act of 1890 increased the government’s silver-buying obligation and further stimulated silver production in Colorado. During the ensuing debate over which precious metals would back US currency, most Coloradans supported silver because Colorado’s silver mines, anchored by booming Leadville and Aspen, were producing some $20 million in silver each year.</p>&#13; &#13; <p>The overproduction of silver had already caused its price to drop by about a quarter when another <a href="http://www.coloradoencyclopedia.org/article/panic-1893"><strong>economic depression hit in 1893</strong>.</a> That year, the US government sought to protect its diminishing gold reserves by halting its silver purchases. After the repeal of the Sherman Silver Purchase Act, the price of silver dropped even further, to about sixty-three cents per ounce by 1894.</p>&#13; &#13; <p>Although the repeal was intended to stimulate the national economy, it devastated Colorado’s. Of the silver mining towns, Leadville suffered the most, with ninety mines closed and 2,500 unemployed. Aspen’s silver boom effectively ended, and the town later had to reinvent itself as a <a href="https://coloradoencyclopedia.org/article/ski-industry"><strong>ski</strong></a> destination to survive. Altogether, more than 9,500 jobs dried up in mining towns across the state. Colorado’s silver industry never recovered, with production dwindling to below $10 million per year after the turn of the century.</p>&#13; &#13; <p><em>Cripple Creek and Consolidation</em></p>&#13; &#13; <p>Although the bane of Colorado’s silver industry, repealing the Sherman Act was a boon for mining gold and other metals. Many out-of-work silver miners flocked to new discoveries in the Cripple Creek gold mines.</p>&#13; &#13; <p>The Cripple Creek district was on the western flank of <a href="http://www.coloradoencyclopedia.org/article/pikes-peak"><strong>Pikes Peak</strong></a>, where local rancher Bob Womack found gold in 1890. With the repeal of the Sherman Act, the value of gold in Colorado increased by about $4 million (40 percent) from 1894 to 1895 and reached a peak of $28 million in 1900, due primarily to Cripple Creek production.</p>&#13; &#13; <p>As in other industries—such as railroads, steel, and petroleum—the precious metals industry began to consolidate in the 1890s. This led to the creation of large companies that controlled both mines and smelters. Formed in 1899, the <strong>American Smelting and Refining Company</strong> (ASARCO) was the most significant of these companies in Colorado, operating the <strong>Globe smelter</strong> in Denver, the Arkansas Valley smelter in Leadville, and the <strong>Colorado smelter</strong> in <a href="http://www.coloradoencyclopedia.org/article/pueblo"><strong>Pueblo</strong></a>, as well as dozens of mines across the state. Several years later, ASARCO also acquired the Guggenheim family’s smelters at those locations, creating a near-monopoly in Colorado’s smelting industry.</p>&#13; &#13; <p><em>Twentieth Century</em></p>&#13; &#13; <p>Thereafter, the amount of gold produced in Colorado began to taper off, dropping from 20 million ounces in 1900 to 8.5 million by 1910, then down to 5.4 million ounces in 1920. Gold’s value, however, remained steady throughout the 1910s, hovering around $20 million for the better part of the decade. Its value declined as English investors pulled out of Colorado mines to support their home nation during <a href="http://www.coloradoencyclopedia.org/article/colorado-world-war-i"><strong>World War I</strong></a>.</p>&#13; &#13; <p>In the 1910s, dredging provided hope for gold mining outfits in five Colorado counties. Dredging used a mechanical chain of buckets attached to a boom on a huge flat-bottom barge floating on a self-dug pond. The dredge buckets scooped large volumes of riverbed gravel into an onboard sluice, where gold was separated. The “waste” gravel was then stacked by a conveyor belt in huge dredge piles still visible along the Blue River near Breckenridge and southeast of <a href="/article/fairplay"><strong>Fairplay</strong></a>. Although it did not bring gold mining back to its heyday, dredging yielded modest gold production in <a href="http://www.coloradoencyclopedia.org/article/summit-county"><strong>Summit</strong></a> and <a href="http://www.coloradoencyclopedia.org/article/park-county"><strong>Park</strong></a> Counties through the early 1940s, when the federal government halted gold mining during <strong>World War II</strong>.</p>&#13; &#13; <p>Meanwhile, with mine production continuing to fall, most Colorado silver-lead-zinc smelters had been shut down by the late 1920s, leaving only one Leadville and one Denver facility in operation. Fewer smelters meant higher costs for transporting ore, making it even harder to turn a profit on the lower-grade ore that remained. Gold and silver production and values dwindled. To compensate, the US Mint stopped coining gold in 1933 and raised the price from $20 per troy ounce to $35 per troy ounce, where it remained until 1972.</p>&#13; &#13; <p>After the war, gold and silver became mere nuggets in the state’s mining stream, which was dominated by <strong>molybdenum </strong>and <a href="https://coloradoencyclopedia.org/article/uranium-mining"><strong>uranium</strong></a>. The last underground mine in the Cripple Creek District shut down in 1964. By 1975, when US citizens could again own gold bullion, Colorado still produced some $5.4 million in gold annually. However, along with silver, gold was primarily a by-product of mining for other, more profitable metals. Colorado’s molybdenum production, for instance, was $183 million that year.</p>&#13; &#13; <h2>Labor Strife</h2>&#13; &#13; <p>As the precious-metal mining industry consolidated in the late nineteenth century, the era of the individual prospector rushing to strike it rich came to an end, replaced by the grueling drudgery of workers mining for a company. Hard-rock mining was dangerous, with daily hazards including rock falls, injuries from drills and other equipment, and dynamite blasts. As mining historian Duane Smith put it, many accidents and injuries stemmed from “general rashness and lack of care” on behalf of the companies and fellow workers. In addition, many miners developed silicosis, a deadly lung disease caused by inhaling tiny rock particles all day. By 1900 miners braved all these risks for an average of about three dollars per eight-hour day, paltry earnings compared to those of the company bosses.</p>&#13; &#13; <p>Disgruntled hard-rock miners joined the <a href="http://www.coloradoencyclopedia.org/article/western-federation-miners"><strong>Western Federation of Miners</strong></a> (WFM), which lobbied for better pay and working conditions and organized strikes in such places as <a href="https://coloradoencyclopedia.org/article/leadville-strike-1896%E2%80%9397"><strong>Leadville</strong></a>, <strong>Cripple Creek</strong>, and <strong>Telluride</strong>. The tensions that stemmed from the miners’ exploited condition sometimes boiled over into outright labor conflict, such as when WFM members in Cripple Creek blew up a train platform where strikebreakers arrived in 1894 or when striking miners shot at and bombed strikebreakers in Leadville in 1896. For all their organizing and sacrifice, miners’ gains in this period were relatively small; slight pay increases, as well as the state’s implementation of an eight-hour workday in 1899, were among their victories—although subsequent strikes proved necessary to get mine owners to follow the law.</p>&#13; &#13; <h2>Today</h2>&#13; &#13; <p><em>Production</em></p>&#13; &#13; <p>Although it is far from being as profitable as it was in the nineteenth century, gold and silver mining continues in Colorado today. After a brief hiatus in the 1960s, gold and silver mining resumed at the Cripple Creek and Victor Mine in the late 1970s. Today the mine produces about 322,000 ounces of gold and silver each year. While this is nothing compared to the 25 million ounces pulled out of Colorado mines in 1893, its value—some $580 million at a rate of roughly $1,800 per troy ounce—is still substantial.</p>&#13; &#13; <p>Mine operators still use milling technology to crush the ore to a usable size. From there, the Cripple Creek and Victor Mine now use a process called <em>heap-leaching </em>to recover gold from ore instead of cyanide vats. In heap-leaching, the ore is crushed into sand, piled up, and dripped with a cyanide solution that causes the metals to dissolve and leach into a catchment pond, where the gold can be recovered, and the cyanide reused.</p>&#13; &#13; <p><em>Legacy</em></p>&#13; &#13; <p>Gold and silver mining played an essential role in the development of modern Colorado, but it also touched off a statewide environmental crisis that is ongoing today. Acid mine drainage—the breakdown and leaching of sulfide metals from mine workings, mine waste rock, and mill tailings into local water sources—became a concern in the late twentieth century due to the Clean Water Act and similar environmental laws. This has resulted in lawsuits against mining companies and the creation of several <strong>Superfund sites in Colorado</strong> where the US <strong>Environmental Protection Agency</strong> (EPA) has worked to contain and treat contaminated water from mining districts.</p>&#13; &#13; <p>Although the EPA is tasked with cleaning up mines with acidic drainage, the agency has sometimes caused further damage. In 2015, EPA crews <a href="https://coloradoencyclopedia.org/article/gold-king-mine-spill"><strong>accidentally released</strong></a> some 3 million gallons of metal-contaminated water into the <a href="http://www.coloradoencyclopedia.org/article/animas-river"><strong>Animas River</strong></a>. That spill, originating from the <strong>Gold King Mine</strong> north of Durango, demonstrated the risk of modern environmental disasters arising from nineteenth-century gold and silver mining in Colorado.</p>&#13; &#13; <p>In addition to the mines themselves, processing precious metals also produced environmental problems. Emissions from smelters caused localized acid rain; the emissions, as well as the waste material from smelting called <em>slag</em>, contained high levels of arsenic and lead, both harmful to human health. Multiple smelter locations across the state, including in Denver’s <strong>Globeville</strong> neighborhood and in Pueblo, became Superfund cleanup sites in the late twentieth and early twenty-first centuries, with the EPA and in some cases, the smelting company working to remove contaminated soil and slag piles.</p>&#13; &#13; <p>However, the legacy of Colorado’s precious-metal mines also continues in other, more positive ways. As a result of its durability and malleability, much of the gold mined in Colorado during the 1800s is still in use today, whether in jewelry, electronics, space probes, or the treasury reserves of nations across the globe. And the silver, used in US coins until 1972 and in film processing until the 1990s, is now found in jewelry and high-conductivity electronic circuits. Although more than 160 years have passed since the Colorado Gold Rush began, the sun’s gleam off the <a href="https://coloradoencyclopedia.org/article/colorado-state-capitol"><strong>State Capitol</strong></a>’s gold dome continues to reflect the state’s mining heritage.</p>&#13; </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-author--encyclopedia-article.html.twig * field--node--field-author.html.twig x field--node--encyclopedia-article.html.twig * field--field-author.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-author field--type-entity-reference field--label-above" id="id-field-author"> <div class="field__label" id="id-field-author">Author</div> <div class='field__items'> <div class="field__item" id="id-field-author"><a href="/author/encyclopedia-staff" hreflang="und">Encyclopedia Staff</a></div> <div class="field__item" id="id-field-author"><a href="/author/hart-steve" hreflang="und">Hart, Steve</a></div> <div class="field__item" id="id-field-author"><a href="/author/fell-james-e" hreflang="und">Fell, James E.</a></div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-keyword--encyclopedia-article.html.twig * field--node--field-keyword.html.twig x field--node--encyclopedia-article.html.twig * field--field-keyword.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-keyword field--type-entity-reference field--label-above" id="id-field-keyword"> <div class="field__label" id="id-field-keyword">Keywords</div> <div class='field__items'> <div class="field__item" id="id-field-keyword"><a href="/keyword/gold-mining-colorado" hreflang="en">gold mining colorado</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/silver-mining-colorado" hreflang="en">silver mining colorado</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/metal-mining" hreflang="en">metal mining</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/mining" hreflang="en">mining</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/acid-mine-drainage" hreflang="en">acid mine drainage</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/telluride" hreflang="en">Telluride</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/black-hawk" hreflang="en">Black Hawk</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/cripple-creek" hreflang="en">Cripple Creek</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/aspen" hreflang="en">Aspen</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/leadville" hreflang="en">Leadville</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/railroads" hreflang="en">railroads</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/smelter" hreflang="en">smelter</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/colorado-springs" hreflang="en">colorado springs</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/breckenridge" hreflang="en">Breckenridge</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/boulder" hreflang="en">boulder</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/boulder-county" hreflang="en">boulder county</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/niwot" hreflang="en">Niwot</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/cheyenne" hreflang="en">cheyenne</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/arapaho" hreflang="en">arapaho</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/indian-removal" hreflang="en">indian removal</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/hosa" hreflang="en">hosa</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/ute" hreflang="en">ute</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/brunot-agreement" hreflang="en">Brunot Agreement</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/san-juan-mountains" hreflang="en">San Juan Mountains</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/silverton" hreflang="en">Silverton</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/durango" hreflang="en">Durango</a></div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'links__node' --> <!-- FILE NAME SUGGESTIONS: * links--node.html.twig x links--inline.html.twig * links--node.html.twig * links.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/navigation/links--inline.html.twig' --> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/navigation/links--inline.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-references-html--encyclopedia-article.html.twig * field--node--field-references-html.html.twig x field--node--encyclopedia-article.html.twig * field--field-references-html.html.twig * field--text-long.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-references-html field--type-text-long field--label-above" id="id-field-references-html"> <div class="field__label" id="id-field-references-html">References</div> <div class="field__item" id="id-field-references-html"><p>American Museum of Natural History, “<a href="https://www.amnh.org/exhibitions">Forming Deposits</a>,” n.d.</p>&#13; &#13; <p>Vladimir Basov, “<a href="https://www.mining.com/heap-leach-minings-breakthrough-technology/">Heap Leach: Mining’s breakthrough technology</a>,” Mining.com, August 20, 2015.</p>&#13; &#13; <p>“<a href="http://www.asarco.com/about-us/company-history/">Company History</a>,” ASARCO, n.d.</p>&#13; &#13; <p>“<a href="https://www.newmont.com/operations-and-projects/global-presence/north-america/cripple-creek-victor-us/default.aspx">Cripple Creek &amp; Victor</a>,” Newmont Mining, updated 2019.</p>&#13; &#13; <p>James E. Fell and Eric Twitty, “<a href="https://www.historycolorado.org/sites/default/files/media/document/2017/651.pdf">The Mining Industry in Colorado</a>,” National Register of Historic Places Multiple Property Documentation Form, OMB No. 1024-0018 (March 1992).</p>&#13; &#13; <p>Charles W. Henderson, “<a href="https://pubs.usgs.gov/pp/0138/report.pdf">Mining in Colorado: A History of Discovery, Development and Production</a>,” USGS Professional Paper 138 (Washington, DC: Government Printing Office, 1926).</p>&#13; &#13; <p>Hobart M. King, “<a href="https://geology.com/minerals/silver.shtml">Silver</a>,” Geology.com, n.d.</p>&#13; &#13; <p>Terry Norgate and Nawshad Haque, “Using life cycle assessment to evaluate some environmental impacts of gold production,” <em>Journal of Cleaner Production</em> 29-30 (July 2012).</p>&#13; &#13; <p>“<a href="https://www2.census.gov/library/publications/decennial/1860/population/1860a-38.pdf">Population of the United States in 1860: Territory of Colorado</a>,” US Census Bureau, 1860.</p>&#13; &#13; <p>“<a href="https://www.atsdr.cdc.gov/hac/coloradoslag.html#:~:text=The%20waste%20materials%20were%20then,the%20only%20ones%20at%20risk.">Pueblo, CO Exposure Investigation Success Story</a>,” Agency for Toxic Substances and Disease Registry, updated April 11, 2018.</p>&#13; &#13; <p>Laura Shunk, “<a href="https://www.westword.com/restaurants/globeville-was-a-superfund-site-could-we-garden-there-10767357">Here’s the Dirt on Gardening in Globeville</a>,” <em>Westword</em>, September 12, 2018. Virginia McConnell Simmons, <em>The Ute Indians of Utah, Colorado, and New Mexico </em>(Boulder: University Press of Colorado, 2000).</p>&#13; &#13; <p>Duane A. Smith, <em>The Trail of Gold &amp; Silver: Mining in Colorado, 1859–2009 </em>(Boulder: University Press of Colorado, 2009).</p>&#13; &#13; <p>US Environmental Protection Agency, “<a href="https://www.epa.gov/enforcement/case-summary-epa-funded-sites-and-communities-asarco-bankruptcy-settlement">Case Summary: EPA Funded Sites and Communities in the ASARCO Bankruptcy Settlement</a>,” n.d.</p>&#13; &#13; <p>US Environmental Protection Agency, “<a href="https://semspub.epa.gov/work/08/312995.pdf">Fact Sheet: Yak Tunnel Cleanup—California Gulch Superfund Site</a>,” April 1989.</p>&#13; &#13; <p>US Environmental Protection Agency, “<a href="https://cumulis.epa.gov/supercpad/SiteProfiles/index.cfm?fuseaction=second.cleanup&amp;id=0802700">Superfund Site: Colorado Smelter—Pueblo, CO—Cleanup Activities</a>,” n.d.</p>&#13; &#13; <p>Elliott West, <em>The Contested Plains: Indians, Goldseekers, and the Rush to Colorado </em>(Lawrence: University Press of Kansas, 1998).</p>&#13; </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-additional-information-htm--encyclopedia-article.html.twig * field--node--field-additional-information-htm.html.twig x field--node--encyclopedia-article.html.twig * field--field-additional-information-htm.html.twig * field--text-long.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-additional-information-htm field--type-text-long field--label-above" id="id-field-additional-information-htm"> <div class="field__label" id="id-field-additional-information-htm">Additional Information</div> <div class="field__item" id="id-field-additional-information-htm"><p>Carl Abbott, Stephen J. Leonard, and Thomas J. Noel, <em>Colorado: A History of the Centennial State </em>5th ed. (Boulder: University Press of Colorado, 2013).</p>&#13; &#13; <p>James E. Fell, <em>Ores to Metals: The Rocky Mountain Smelting Industry </em>(Boulder: University Press of Colorado, 2009).</p>&#13; &#13; <p>William Henry Jackson and John Fielder, <em>Colorado: 1870–2000 </em>(Silverthorne, CO: John Fielder Publishing, 2015).</p>&#13; </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> Tue, 09 Aug 2022 17:55:06 +0000 yongli 3721 at http://coloradoencyclopedia.org Sand Wash Basin Tool Stone Sites http://coloradoencyclopedia.org/article/sand-wash-basin-tool-stone-sites <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--title--encyclopedia-article.html.twig x field--node--title.html.twig * field--node--encyclopedia-article.html.twig * field--title.html.twig * field--string.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <span class="field field--name-title field--type-string field--label-hidden">Sand Wash Basin Tool Stone Sites</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--uid--encyclopedia-article.html.twig x field--node--uid.html.twig * field--node--encyclopedia-article.html.twig * field--uid.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--uid.html.twig' --> <span class="field field--name-uid field--type-entity-reference field--label-hidden"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'username' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/user/username.html.twig' --> <span lang="" about="/users/yongli" typeof="schema:Person" property="schema:name" datatype="">yongli</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/user/username.html.twig' --> </span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--uid.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--created--encyclopedia-article.html.twig x field--node--created.html.twig * field--node--encyclopedia-article.html.twig * field--created.html.twig * field--created.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--created.html.twig' --> <span class="field field--name-created field--type-created field--label-hidden"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'time' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/time.html.twig' --> <time datetime="2020-03-18T22:34:26-06:00" title="Wednesday, March 18, 2020 - 22:34" class="datetime">Wed, 03/18/2020 - 22:34</time> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/time.html.twig' --> </span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--created.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'addtoany_standard' --> <!-- FILE NAME SUGGESTIONS: * addtoany-standard--node--encyclopedia-article.html.twig * addtoany-standard--node.html.twig x addtoany-standard.html.twig --> <!-- BEGIN OUTPUT from 'modules/contrib/addtoany/templates/addtoany-standard.html.twig' --> <span class="a2a_kit a2a_kit_size_32 addtoany_list" data-a2a-url="http://coloradoencyclopedia.org/article/sand-wash-basin-tool-stone-sites" data-a2a-title="Sand Wash Basin Tool Stone Sites"><a class="a2a_dd addtoany_share" href="https://www.addtoany.com/share#url=http%3A%2F%2Fcoloradoencyclopedia.org%2Farticle%2Fsand-wash-basin-tool-stone-sites&amp;title=Sand%20Wash%20Basin%20Tool%20Stone%20Sites"></a><a class="a2a_button_facebook"></a><a class="a2a_button_twitter"></a><a class="a2a_button_email"></a></span> <!-- END OUTPUT from 'modules/contrib/addtoany/templates/addtoany-standard.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--body--encyclopedia-article.html.twig * field--node--body.html.twig x field--node--encyclopedia-article.html.twig * field--body.html.twig * field--text-with-summary.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-body field--type-text-with-summary field--label-hidden field__item" id="id-body"><p align="left">Located northwest of Craig in <a href="https://coloradoencyclopedia.org/article/moffat-county"><strong>Moffat County</strong></a>, the Sand Wash Basin is an area of Bridger Formation rock outcrops that prehistoric peoples mined extensively as a source for stones to make tools with. Bridger Formation chert is typically light to dark brown, though some of the chert in the basin is referred to as “tiger chert” because of its distinct alternating light and dark brown banding. Tiger cherts have been found across Colorado and in both Utah and Wyoming. The distinct patterning of tiger chert has allowed archaeologists to trace the movement of prehistoric people in and out of northwestern Colorado.</p>&#13; &#13; <h2 align="left">Geology</h2>&#13; &#13; <p align="left">The Sand Wash Basin is the southern portion of the Green River Basin system in Wyoming, which is an Eocene-aged lake system that drained south into the Piceance Basin of Colorado and the Uinta Basin of Utah. Deposits in the Sand Wash Basin are sedimentary and contain many fossils, including well-preserved vertebrate, invertebrate, and plant fossils. Because of high silica content in the region’s geology, the Sand Wash Basin contains layers of chert bedrock, chert nodules, petrified wood, and fossilized stromatolites that lend themselves to striped banding.</p>&#13; &#13; <p align="left">There are different varieties of chert tool-<a href="https://coloradoencyclopedia.org/article/prehistoric-stone-quarrying-colorado"><strong>stone quarries</strong></a> in the Sand Wash Basin. The basin’s center contains bedrock layers of chert. The basin’s perimeter contains more nodules of petrified wood and stromatolites that are available as eroded gravel deposits and isolated clusters. Whether quarried from layers of chert bedrock or collected from erosional deposits, all the stone material in the basin was usable for tool blanks and is typically identified as Bridger Formation chert.</p>&#13; &#13; <h2 align="left">Archaeology</h2>&#13; &#13; <p align="left">In 1976 Richard Stucky did an archaeological survey of the Sand Wash Basin. Stucky noted that the basin’s Bridger Formation cherts had a long history of use and can be associated with the bison-hunting <a href="https://coloradoencyclopedia.org/article/paleo-indian-period"><strong>Paleo-Indian</strong></a> and <a href="https://coloradoencyclopedia.org/article/clovis"><strong>Clovis</strong></a> populations of 13,000 years ago as well as later <a href="https://coloradoencyclopedia.org/article/archaic-period-colorado"><strong>Archaic</strong></a>, <a href="https://coloradoencyclopedia.org/article/formative-period-prehistory"><strong>Formative</strong></a>, and historical groups, including the Shoshone and <a href="https://coloradoencyclopedia.org/article/northern-ute-people-uintah-and-ouray-reservation"><strong>Ute</strong></a>. In some places in the basin one can still see the large quantities of stone that were quarried and tested by prehistoric inhabitants of the area. One additional piece of evidence for a long period of use of the basin’s cherts comes from the <a href="https://coloradoencyclopedia.org/image/boulder-artifacts"><strong>Mahaffy cache</strong></a> site in <a href="https://coloradoencyclopedia.org/article/boulder"><strong>Boulder</strong></a>, with its impressive tiger chert artifacts. Stucky suggested that prehistoric families camped around the periphery of the Sand Wash Basin while mining resources in the middle of it, which was supported by a subsequent archaeological study in 2010. Stucky’s work resulted in a collection of pristine materials now housed at the <a href="https://coloradoencyclopedia.org/article/denver-museum-nature-science-0"><strong>Denver Museum of Nature and Science</strong></a>, including a fourteen-centimeter-long cold-worked copper knife found at the Cathedral Butte site, which is similar to knives found in Oklahoma and the Great Lakes region.</p>&#13; &#13; <p align="left">Bridger Formation chert artifacts have been found in archaeological sites in neighboring states, such as the John Gale Cache in Wyoming and <a href="https://coloradoencyclopedia.org/article/fremont-culture"><strong>Fremont</strong></a> villages in western Colorado and Utah, and archaeologists are studying their chemical structure to connect these artifacts to specific quarries in the Sand Wash Basin. Interestingly, heating the Bridger Formation chert in a fire alters its structure and makes it easier to shape into a tool. While this can create sharper tools, it can also crack the chert and make it more brittle. The heat-treating of cherts has been shown to occur more often around the periphery of the Sand Wash Basin than in the heart of the Sand Wash Basin, though it is unknown how heat-treating alters the ability of scientists to source the Bridger Formation chert to specific quarries.</p>&#13; &#13; <p align="left">Bridger Formation cherts from the Sand Wash Basin help archaeologists understand the way prehistoric families lived and moved through Colorado over the last 13,000 years. Beyond that strong archaeological value, tiger chert artifacts can be beautiful examples of prehistoric craftsmanship. Thus, in addition to being utilitarian tools that now serve as markers of trade and antiquity, they were likely admired and appreciated for their striking visual characteristics as much in the past as they are today.</p>&#13; </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-author--encyclopedia-article.html.twig * field--node--field-author.html.twig x field--node--encyclopedia-article.html.twig * field--field-author.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-author field--type-entity-reference field--label-above" id="id-field-author"> <div class="field__label" id="id-field-author">Author</div> <div class='field__items'> <div class="field__item" id="id-field-author"><a href="/author/landt-matthew" hreflang="und">Landt, Matthew</a></div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-keyword--encyclopedia-article.html.twig * field--node--field-keyword.html.twig x field--node--encyclopedia-article.html.twig * field--field-keyword.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-keyword field--type-entity-reference field--label-above" id="id-field-keyword"> <div class="field__label" id="id-field-keyword">Keywords</div> <div class='field__items'> <div class="field__item" id="id-field-keyword"><a href="/keyword/archaeology" hreflang="en">archaeology</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/prehistoric-native-americans" hreflang="en">prehistoric Native Americans</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/stone-tools" hreflang="en">stone tools</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/chert" hreflang="en">chert</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/bridger-formation" hreflang="en">Bridger formation</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/geology" hreflang="en">geology</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/colorado-geology" hreflang="en">colorado geology</a></div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'links__node' --> <!-- FILE NAME SUGGESTIONS: * links--node.html.twig x links--inline.html.twig * links--node.html.twig * links.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/navigation/links--inline.html.twig' --> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/navigation/links--inline.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-references-html--encyclopedia-article.html.twig * field--node--field-references-html.html.twig x field--node--encyclopedia-article.html.twig * field--field-references-html.html.twig * field--text-long.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-references-html field--type-text-long field--label-above" id="id-field-references-html"> <div class="field__label" id="id-field-references-html">References</div> <div class="field__item" id="id-field-references-html"><p align="left"><a name="_ENREF_1" id="_ENREF_1">H. P. Buchheim, L. R. Brand, and H. T. Goodwin, “Lacustrine to fluvial floodplain deposition in the Eocene Bridger Formation,” <em>Palaeogeography, Palaeoclimatology, Palaeoecology</em> 162 (September 2000).</a></p>&#13; &#13; <p align="left">Neil Hauser, “Sourcing Bridger Chert With Laser Breakdown Spectroscopy, Technical report, Advanced Technical Solutions for Archaeology and Anthropology, Centennial, Colorado” (Montrose, CO: Alpine Archaeological Consultants, 2013).</p>&#13; &#13; <p align="left"><a name="_ENREF_3" id="_ENREF_3">Brian R. Ingalls and Lisa E. Park, “Biotic and Taphonomic Response to Lake-Level Fluctuations in the Greater Green River Basin (Eocene), Wyoming,” <em>Palaios</em> 25 (May 2010).</a></p>&#13; &#13; <p align="left">Matthew J. Landt, “Class III Survey of Select Areas in Sand Wash Basin, Moffat County, Colorado, Technical report, Alpine Archaeological Consultants, Inc., Montrose, Colorado” (Craig: Vermillion Chapter, Colorado Archaeological Society, and Bureau of Land Management, Little Snake Field Office, 2011).</p>&#13; &#13; <p align="left">Matthew J. Landt and Robyn Watkins Morris, “Lithic Procurement in the Sand Wash Basin of Northwestern Colorado: How Unpredictability Highlights Adaptations,” <em>Plains Anthropologist</em> 63 (February 2018).</p>&#13; &#13; <p align="left">Byron Loosle, “The Acquisition of Nonlocal Lithic Material by the Uinta Fremont,” <em>Journal of California and Great Basin Anthropology</em> 22, no. 2 (2000).</p>&#13; &#13; <p align="left"><a name="_ENREF_4" id="_ENREF_4">James C. Miller, “Lithic Resources,” in <em>Prehistoric Hunters of the High Plains</em>, ed. George C. Frison (San Diego: Academic Press, 1991).</a></p>&#13; &#13; <p align="left">Mark E. Miller, Michael D. Stafford, and George W. Brox, “The John Gale Site Biface Cache,” <em>Plains Anthropologist</em> 36 (February 1991).</p>&#13; &#13; <p align="left"><a name="_ENREF_5" id="_ENREF_5">Paul C. Murphey and David Daitch, “</a><a href="https://publications.anl.gov/anlpubs/2009/02/63538.pdf">Paleontological Overview of Oil Shale and Tar Sands Areas in Colorado, Utah, and Wyoming</a>,” Technical report for US Department of the Interior, Bureau of Land Management (Argonne, IL: Argonne National Laboratory, December 2007).</p>&#13; &#13; <p align="left"> </p>&#13; &#13; <p align="left"><a name="_ENREF_6" id="_ENREF_6">M. Elliot Smith, Alan R. Carroll, and Brad S. Singer, “Synoptic Reconstruction of a Major Ancient Lake System: Eocene Green River Formation, Western United States,” GSA Bulletin 120 (January–February 2008).</a></p>&#13; &#13; <p align="left"><a name="_ENREF_7" id="_ENREF_7">Richard K. Stucky, et al., “Magnetic Stratigraphy, Sedimentology, and Mammalian Faunas of the Early Uintan Washakie Formation, Sand Wash Basin, Northwestern Colorado,” in <em>The Terrestrial Eocene-Oligocene Transition in North America</em>, ed. Donald R. Prothero (New York: Cambridge University Press,1996).</a></p>&#13; &#13; <p><a name="_ENREF_8" id="_ENREF_8">Richard Keith Stucky, “Archaeological Survey of the Sand Wash Basin, Northwestern Colorado” (MA thesis, University of Colorado–Boulder, 1977).</a></p>&#13; </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-additional-information-htm--encyclopedia-article.html.twig * field--node--field-additional-information-htm.html.twig x field--node--encyclopedia-article.html.twig * field--field-additional-information-htm.html.twig * field--text-long.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-additional-information-htm field--type-text-long field--label-above" id="id-field-additional-information-htm"> <div class="field__label" id="id-field-additional-information-htm">Additional Information</div> <div class="field__item" id="id-field-additional-information-htm"><p>Claire Cleveland, “<a href="https://www.cpr.org/2020/03/16/gunnison-county-effectively-shutting-down-public-life-to-fight-covid-19/">Gunnison County Effectively Shutting Down Public Life To Fight COVID-19</a>,” Colorado Public Radio, March 16, 2020.</p>&#13; &#13; <p>Shaun Yuan, “<a href="https://www.aljazeera.com/news/2020/3/17/in-china-life-returning-to-normal-as-coronavirus-outbreak-slows">In China, life returning to normal as coronavirus outbreak slows</a>,” <em>Al Jazeera</em>, March 17, 2020.</p>&#13; </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> Thu, 19 Mar 2020 04:34:26 +0000 yongli 3196 at http://coloradoencyclopedia.org Barger Gulch Site http://coloradoencyclopedia.org/article/barger-gulch-site <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--title--encyclopedia-article.html.twig x field--node--title.html.twig * field--node--encyclopedia-article.html.twig * field--title.html.twig * field--string.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <span class="field field--name-title field--type-string field--label-hidden">Barger Gulch Site</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--uid--encyclopedia-article.html.twig x field--node--uid.html.twig * field--node--encyclopedia-article.html.twig * field--uid.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--uid.html.twig' --> <span class="field field--name-uid field--type-entity-reference field--label-hidden"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'username' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/user/username.html.twig' --> <span lang="" about="/users/yongli" typeof="schema:Person" property="schema:name" datatype="">yongli</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/user/username.html.twig' --> </span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--uid.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--created--encyclopedia-article.html.twig x field--node--created.html.twig * field--node--encyclopedia-article.html.twig * field--created.html.twig * field--created.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--created.html.twig' --> <span class="field field--name-created field--type-created field--label-hidden"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'time' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/time.html.twig' --> <time datetime="2020-01-15T15:28:06-07:00" title="Wednesday, January 15, 2020 - 15:28" class="datetime">Wed, 01/15/2020 - 15:28</time> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/time.html.twig' --> </span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--created.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'addtoany_standard' --> <!-- FILE NAME SUGGESTIONS: * addtoany-standard--node--encyclopedia-article.html.twig * addtoany-standard--node.html.twig x addtoany-standard.html.twig --> <!-- BEGIN OUTPUT from 'modules/contrib/addtoany/templates/addtoany-standard.html.twig' --> <span class="a2a_kit a2a_kit_size_32 addtoany_list" data-a2a-url="http://coloradoencyclopedia.org/article/barger-gulch-site" data-a2a-title="Barger Gulch Site"><a class="a2a_dd addtoany_share" href="https://www.addtoany.com/share#url=http%3A%2F%2Fcoloradoencyclopedia.org%2Farticle%2Fbarger-gulch-site&amp;title=Barger%20Gulch%20Site"></a><a class="a2a_button_facebook"></a><a class="a2a_button_twitter"></a><a class="a2a_button_email"></a></span> <!-- END OUTPUT from 'modules/contrib/addtoany/templates/addtoany-standard.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--body--encyclopedia-article.html.twig * field--node--body.html.twig x field--node--encyclopedia-article.html.twig * field--body.html.twig * field--text-with-summary.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-body field--type-text-with-summary field--label-hidden field__item" id="id-body"><p>There are few places in western North America richer in <a href="/article/paleo-indian-period"><strong>Paleo-Indian</strong></a> archaeology than <a href="/article/grand-county"><strong>Middle Park</strong></a>, the valley that forms the headwaters of the <a href="http://www.coloradoencyclopedia.org/article/colorado-river"><strong>Colorado River</strong></a> in <a href="/article/grand-county"><strong>Grand County</strong></a>. Within Middle Park, the Barger Gulch area preserves an impressive amount of evidence from early humans, with sites dating from roughly 12,900 to 10,000 years ago. Barger Gulch is a small, spring-fed tributary of the Colorado River, flowing south to north, draining an area east of Junction Butte, and joining the Colorado River about four miles east of <strong>Kremmling</strong>. In all, eleven Paleo-Indian localities have been documented along this drainage. Artifacts in the Barger Gulch area span the Paleo-Indian period with one exception— no <a href="https://coloradoencyclopedia.org/article/clovis"><strong>Clovis</strong></a> archaeology has yet been found in Middle Park, though <a href="https://coloradoencyclopedia.org/article/folsom-people"><strong>Folsom</strong></a>, the period that follows Clovis, is abundant.</p> <h2>Natural History</h2> <p>If you were to visit the Barger Gulch area today, you would find it to be a nondescript and fairly uninviting area. The high, flat surface that begins on the margins of the Colorado River Valley and slowly slopes upward to the south is covered with a sea of <a href="/article/sagebrush"><strong>sagebrush</strong></a> and grass with an occasional isolated <a href="/article/conifers"><strong>juniper or Douglas fir</strong></a> on north-facing slopes. It is one of the driest parts of Middle Park. Barger Gulch has a modest flow and has cut deeply through Miocene Troublesome Formation bedrock. As inhospitable as the place appears today, the archaeology suggests that it was a good place to live more than 10,000 years ago because people in that period returned to the area time and again. One of the attractions comes straight from the bedrock—Troublesome Formation chert, used to make stone tools.</p> <p>During the Miocene, approximately 20 to 5 million years ago, the valley of Middle Park was filling with sediments, and one major source of sedimentation was volcanism. Some of the ashy sediments that filled the basin later were transformed into a fine-grained silicate rock called chert, ideal for the manufacture of stone tools. Large amounts of Troublesome Formation chert, also known as Kremmling Chert, can be found in the Barger Gulch area, and all of the nearby archaeological localities are dominated by this material. Chert was one clear attraction.</p> <h2>Ancient Camp</h2> <p>The most intensively studied part of the Barger Gulch site is called Locality B, a large Folsom campsite dating to around 12,760 years ago. Locality B is remarkable for its large numbers of chipped stone artifacts, with an assemblage totaling more than 75,000 pieces. The types of nonlocal lithic raw materials recovered show that people moved into Barger Gulch from areas east and west of the <a href="/article/rocky-mountains"><strong>Rocky Mountains</strong></a>.</p> <p>Paleo-Indian peoples are renowned for the distances they moved in their seasonal rounds, but occasionally, and likely seasonally, they settled down in one spot for an extended duration of time. Barger Gulch is one of a handful of sites that show this less mobile side of early Paleo-Indian life. In the winter, large mammals are snowed out of high-elevation regions, and their density in winter grazing areas in valley bottoms increases dramatically. Current evidence suggests that the Barger Gulch site represents one or multiple cold-season occupations by Folsom hunter-gatherers, who probably camped in the valley bottom for several weeks to take advantage of <a href="/article/bison"><strong>bison</strong></a> herds wintering in Middle Park. During the winter, Folsom hunter-gatherers camping in the Barger Gulch area would have had easy access to water, stone, wood, and large game.</p> <h2>Research Findings</h2> <p>Because the Barger Gulch site has a relatively high density of artifacts and well-preserved spatial patterning, archaeologists have used it to examine several poorly studied aspects of human lifeways at the end of the last Ice Age in the Rocky Mountains. The site preserves at least four hearth features, three of which sat within households. This allows for studies of the differences in the use of interior and exterior space. For example, it was found that early-stage flintknapping—the removal of large flakes from the outer portions of chert nodules—mostly took place in exterior spaces. Later-stage knapping, such as the <a href="https://coloradoencyclopedia.org/article/fluted-points-0"><strong>fluting of projectile points</strong></a> and resharpening of tools, occurred inside. There is also evidence for artifacts produced by novice flintknappers at the site, most likely children.</p> <p>The Barger Gulch site was listed on the National Register of Historic Places in 2009.</p> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-author--encyclopedia-article.html.twig * field--node--field-author.html.twig x field--node--encyclopedia-article.html.twig * field--field-author.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-author field--type-entity-reference field--label-above" id="id-field-author"> <div class="field__label" id="id-field-author">Author</div> <div class='field__items'> <div class="field__item" id="id-field-author"><a href="/author/surovell-todd" hreflang="und">Surovell, Todd A.</a></div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-keyword--encyclopedia-article.html.twig * field--node--field-keyword.html.twig x field--node--encyclopedia-article.html.twig * field--field-keyword.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-keyword field--type-entity-reference field--label-above" id="id-field-keyword"> <div class="field__label" id="id-field-keyword">Keywords</div> <div class='field__items'> <div class="field__item" id="id-field-keyword"><a href="/keyword/archaeology" hreflang="en">archaeology</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/prehistoric-archaeology" hreflang="en">prehistoric archaeology</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/folsom" hreflang="en">Folsom</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/colorado-folsom-sites" hreflang="en">colorado folsom sites</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/prehistoric-native-americans" hreflang="en">prehistoric Native Americans</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/stone-tools" hreflang="en">stone tools</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/chert" hreflang="en">chert</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/geology" hreflang="en">geology</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/colorado-geology" hreflang="en">colorado geology</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/grand-county" hreflang="en">Grand County</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/troublesome-formation" hreflang="en">Troublesome formation</a></div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'links__node' --> <!-- FILE NAME SUGGESTIONS: * links--node.html.twig x links--inline.html.twig * links--node.html.twig * links.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/navigation/links--inline.html.twig' --> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/navigation/links--inline.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-references-html--encyclopedia-article.html.twig * field--node--field-references-html.html.twig x field--node--encyclopedia-article.html.twig * field--field-references-html.html.twig * field--text-long.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-references-html field--type-text-long field--label-above" id="id-field-references-html"> <div class="field__label" id="id-field-references-html">References</div> <div class="field__item" id="id-field-references-html"><p>Marcel Kornfeld, <em>The First Rocky Mountaineers: Coloradans Before Colorado</em> (Salt Lake City: University of Utah Press, 2013).</p> <p>Todd A. Surovell and Nicole M. Waguespack, “Folsom Hearth-Centered Use of Space at Barger Gulch, Locality B,” in <em>Frontiers in Colorado Paleoindian Archaeology: From the Dent Site to the Rocky Mountains</em>, ed. Robert H. Brunswig and Bonnie L. Pitblado (Boulder: University of Colorado Press, 2007).</p> <p>Nicole M. Waguespack and Todd A. Surovell, “A Simple Method for Identifying Households Using Lithic Assemblages: A Case Study From a Folsom Campsite in Middle Park, Colorado,” in <em>Lithics in the West: Using Lithic Analysis to Solve Archaeological Problems in Western North America</em>, ed. Douglas H. MacDonald, William Andrefsky Jr., and Pei-Lia Yu (Missoula: University of Montana Press, 2014).</p> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-additional-information-htm--encyclopedia-article.html.twig * field--node--field-additional-information-htm.html.twig x field--node--encyclopedia-article.html.twig * field--field-additional-information-htm.html.twig * field--text-long.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-additional-information-htm field--type-text-long field--label-above" id="id-field-additional-information-htm"> <div class="field__label" id="id-field-additional-information-htm">Additional Information</div> <div class="field__item" id="id-field-additional-information-htm"><p>Bob Raynolds and James Hagadorn, “<a href="https://www.coloradostratigraphy.org/strat-chart/main-strat-chart">Colorado Stratigraphy: Main Strat Chart</a>,” updated October 30, 2018.</p> <p>Todd A. Surovell, <em>Toward a Behavioral Ecology of Lithic Technology</em>: <em>Cases From Paleoindian Archaeology</em> (Tucson: University of Arizona Press, 2009).</p> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> Wed, 15 Jan 2020 22:28:06 +0000 yongli 3122 at http://coloradoencyclopedia.org Colorado Geology http://coloradoencyclopedia.org/article/colorado-geology <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--title--encyclopedia-article.html.twig x field--node--title.html.twig * field--node--encyclopedia-article.html.twig * field--title.html.twig * field--string.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <span class="field field--name-title field--type-string field--label-hidden">Colorado Geology</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: x field--node--field-article-image--encyclopedia-article.html.twig * field--node--field-article-image.html.twig * field--node--encyclopedia-article.html.twig * field--field-article-image.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--field-article-image--encyclopedia-article.html.twig' --> <div id="carouselEncyclopediaArticle" class="carousel slide" data-bs-ride="true"> <div class="carousel-inner"> <div class="carousel-item active"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'node' --> <!-- FILE NAME SUGGESTIONS: * node--937--article-detail-image.html.twig * node--937.html.twig x node--image--article-detail-image.html.twig * node--image.html.twig * node--article-detail-image.html.twig * node.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/content/node--image--article-detail-image.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-encyclopedia-image--image.html.twig * field--node--field-encyclopedia-image.html.twig * field--node--image.html.twig * field--field-encyclopedia-image.html.twig * field--image.html.twig x field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field.html.twig' --> <div class="field field--name-field-encyclopedia-image field--type-image field--label-hidden field__item"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image_formatter' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-formatter.html.twig' --> <a href="/image/roxborough-state-park-colorado"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image_style' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-style.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'image' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image.html.twig' --> <img loading="lazy" src="/sites/default/files/styles/wide/public/Roxborough-State-Park-Colorado-John-Fielder_0.jpg?itok=sZ9KrS1q" width="1090" height="852" alt="" typeof="foaf:Image" class="image-style-wide" /> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image.html.twig' --> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-style.html.twig' --> </a> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/image-formatter.html.twig' --> </div> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field.html.twig' --> <div class="carousel-caption d-none d-md-block"> <h5><a href="/image/roxborough-state-park-colorado" rel="bookmark"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--title--image.html.twig x field--node--title.html.twig * field--node--image.html.twig * field--title.html.twig * field--string.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> <span class="field field--name-title field--type-string field--label-hidden">Roxborough State Park, Colorado</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--title.html.twig' --> </a></h5> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--body--image.html.twig * field--node--body.html.twig * field--node--image.html.twig * field--body.html.twig x field--text-with-summary.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--text-with-summary.html.twig' --> <div class="clearfix text-formatted field field--name-body field--type-text-with-summary field--label-hidden field__item"><p>Much of Colorado was once covered by an ancient seafloor. The vertical red rocks at places like <a href="https://coloradoencyclopedia.org/article/roxborough-state-park-archaeological-district"><strong>Roxborough State Park</strong></a>, west of <a href="/article/denver"><strong>Denver</strong></a>, or the Flatirons west of <a href="https://coloradoencyclopedia.org/article/boulder"><strong>Boulder</strong></a>, are dramatic remnants of that seafloor, pushed up along with the rest of the <a href="/article/rocky-mountains"><strong>Rocky Mountains</strong></a> some 65 million years ago.</p>&#13; </div> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--text-with-summary.html.twig' --> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/content/node--image--article-detail-image.html.twig' --> </div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--field-article-image--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--uid--encyclopedia-article.html.twig x field--node--uid.html.twig * field--node--encyclopedia-article.html.twig * field--uid.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--uid.html.twig' --> <span class="field field--name-uid field--type-entity-reference field--label-hidden"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'username' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/user/username.html.twig' --> <span lang="" about="/users/yongli" typeof="schema:Person" property="schema:name" datatype="">yongli</span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/user/username.html.twig' --> </span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--uid.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--created--encyclopedia-article.html.twig x field--node--created.html.twig * field--node--encyclopedia-article.html.twig * field--created.html.twig * field--created.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--created.html.twig' --> <span class="field field--name-created field--type-created field--label-hidden"> <!-- THEME DEBUG --> <!-- THEME HOOK: 'time' --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/time.html.twig' --> <time datetime="2016-06-24T14:26:50-06:00" title="Friday, June 24, 2016 - 14:26" class="datetime">Fri, 06/24/2016 - 14:26</time> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/time.html.twig' --> </span> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/field/field--node--created.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'addtoany_standard' --> <!-- FILE NAME SUGGESTIONS: * addtoany-standard--node--encyclopedia-article.html.twig * addtoany-standard--node.html.twig x addtoany-standard.html.twig --> <!-- BEGIN OUTPUT from 'modules/contrib/addtoany/templates/addtoany-standard.html.twig' --> <span class="a2a_kit a2a_kit_size_32 addtoany_list" data-a2a-url="http://coloradoencyclopedia.org/article/colorado-geology" data-a2a-title="Colorado Geology"><a class="a2a_dd addtoany_share" href="https://www.addtoany.com/share#url=http%3A%2F%2Fcoloradoencyclopedia.org%2Farticle%2Fcolorado-geology&amp;title=Colorado%20Geology"></a><a class="a2a_button_facebook"></a><a class="a2a_button_twitter"></a><a class="a2a_button_email"></a></span> <!-- END OUTPUT from 'modules/contrib/addtoany/templates/addtoany-standard.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--body--encyclopedia-article.html.twig * field--node--body.html.twig x field--node--encyclopedia-article.html.twig * field--body.html.twig * field--text-with-summary.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-body field--type-text-with-summary field--label-hidden field__item" id="id-body"><p>The Earth beneath the rugged mountains and serene plains of Colorado records an ancient saga. Broad tropical seas teemed with life, while reptiles roamed on shore. Continents converged and collided, building massive mountains, only to be torn apart by the movements of colossal tectonic plates. Volcanoes raged, and scalding fluids carrying dissolved metals churned through fissures to make future riches. A huge lake ebbed and flowed, linked to the fortunes of <a href="https://coloradoencyclopedia.org/article/glaciers"><strong>glaciers</strong></a>, and fields of towering sand dunes grew against walls of new mountains. Even today, in the paper-thin history of civilization, rocks and saturated soils rush downhill to remind us that we live on a restless, dynamic Earth.</p>&#13; &#13; <h2>Tropical Seas and Pangaea</h2>&#13; &#13; <p>Late in the Paleozoic Era, some 300 million years ago, when the Ancestral <a href="/article/rocky-mountains"><strong>Rocky Mountains</strong></a> were being worn by weather to low hills, warm inland seas covered parts of Colorado. Life forms very different from those of today swam and flourished in the waters. Fossil records of those life forms are contained in layers of mudstone and limestone.</p>&#13; &#13; <p>At the end of the Paleozoic Era, the restless continental plates collided again to create the supercontinent Pangaea. As the land rose and a Sahara-like desert of enormous proportions covered the continent, the interior seas retreated. But as large as Pangaea was, it too eventually began to be torn apart by the powerful tectonic forces that made it, and the seas returned. Life on land left distinctive marks, most famously the dinosaur footprints and fossil remains throughout the state.</p>&#13; &#13; <p>As Pangaea fragmented, a breakaway piece called Laurentia drifted westward and a series of collisions with other, smaller continental pieces gave rise to the present-day Rocky Mountains. This phoenix-like rebirth of the Rockies started between 60 and 70 million years ago, during a mountain-building event called the Laramide Orogeny. As the peaks rose, they were eroded by wind, water, and ice. Wind and water carried the material eroded from the mountains, covering the area we now call the<a href="/article/colorado%E2%80%99s-great-plains"><strong> Great Plains</strong></a>. The rise of the Rockies continues today. The sedimentary rocks that formed the floor of the warm inland seas were warped upward against the new mountains, leaving huge triangular cliff facets, locally known as flatirons. From high viewpoints, it is easy to imagine the mountains pushing the flat-lying rocks upward.</p>&#13; &#13; <h2>Creation of Ore Deposits</h2>&#13; &#13; <p>As the tectonic plates jostled and collided, some were pushed deeper into the Earth, where they melted. The newly formed liquid rock burned upward to escape back to the surface, where it created volcanoes and lava fields. The mountains of south-central Colorado host the remains of an enormous ancient supervolcano, one that produced the largest single eruption known in the Earth’s entire geologic history. The single eruption rained volcanic material so fast that the thickly falling layers retained enough heat to weld back into solid rock. The molten material was mixed with gases, and during the eruption, the gigantic cavern below the volcano collapsed back on itself, creating a deep, wide crater approximately one mile deep.</p>&#13; &#13; <p>This supervolcano is named the La Garita Caldera, after a town on the west side of Colorado’s <a href="https://coloradoencyclopedia.org/article/san-luis-valley"><strong>San Luis Valley</strong></a>. The La Garita Caldera is only one of twenty-plus smaller but similar calderas throughout the <a href="https://coloradoencyclopedia.org/article/san-juan-mountains"><strong>San Juan Mountains</strong></a>. The calderas have local names, such as the <a href="https://coloradoencyclopedia.org/article/silverton-0"><strong>Silverton</strong></a>, <a href="/article/lake-city-0"><strong>Lake City</strong></a>, and <a href="/article/creede"><strong>Creede</strong></a> calderas. The calderas are deceptively nestled together in the mountains, with the remnants of their circular outlines hinting at a violent history 25 million years ago.</p>&#13; &#13; <p>The destructive eruptions of the volcanoes gave rise to a important facet of Colorado’s history: its vast mineral wealth, which lured a stampede of miners in the mid-nineteenth century. The molten rock beneath the volcanoes often gave rise to superhot and metal-rich waters that pushed for miles outward into cracks and fissures. The invading hot waters dissolved and reacted with the surrounding rocks to make rich ore deposits of gold, silver, copper, lead, zinc, and many other metal-bearing minerals throughout the state.</p>&#13; &#13; <h2>Great Sand Dunes</h2>&#13; &#13; <p>About 500,000 years ago—not so long ago in geologic time—the San Luis Valley of south-central Colorado was underwater. Lake Alamosa covered much of the valley, in a cycle of filling and drying as glaciers melted and grew again through many ice ages. Former shorelines, bays, and lagoons are still visible in the southern part of the valley, rimming what was once a body of water nearly 2,000 square miles on the surface and perhaps as deep as 200 feet over the present-day city of Alamosa. As the lake bottom filled with sediments and soils, and again with water, the lake’s surface eventually overflowed a natural dam and cut a deep channel that is now part of the Rio Grande Gorge.</p>&#13; &#13; <p>The tallest dune field in the United States lies to the east of ancient Lake Alamosa, protected in the <a href="https://coloradoencyclopedia.org/article/great-sand-dunes-national-park-and-preserve"><strong>Great Sand Dunes National Park</strong></a>. The dunes are believed to have formed after Lake Alamosa drained and prevailing winds blew much of the sand up and out of the lakebed to rest against the <strong>Sangre de Cristo Range</strong>. Today, visitors to the park climb, play, and enjoy what glaciers, winds, and water brought to a pocket in the mountains.</p>&#13; &#13; <h2>Plateaus of Western Colorado</h2>&#13; &#13; <p>To the west of the Rocky Mountains in Colorado is a region called the <a href="https://coloradoencyclopedia.org/article/western-slope"><strong>Western Slope</strong></a>. Remnants of ancient seas are also present. These ancient-sea sedimentary rocks are warped upwards in some areas with flatiron forms similar to the ones on the Eastern Slope. Where the rocks are still flat-lying, there is often a cap of younger lava, a dark-colored rock called basalt that resists weathering and erosion. The basalt creates a protective cap over the softer underlying rocks, forming distinctive flat-topped hills called mesas (Spanish for “tables”). The largest of these mesas is <strong>Grand Mesa</strong> just east of <a href="/article/grand-junction"><strong>Grand Junction</strong></a>. The mesas are often dotted with small lakes and covered with trees, providing important surface and groundwater reservoirs. Hardened sandstones also cap softer rocks in some areas, forming dramatic pillar shapes, explained by some as supernatural. In formations such as the Book Cliffs north of Grand Junction, massive cliffs tower like toppled tomes, with durable mesa covers binding pages of the Earth’s history.</p>&#13; &#13; <h2>Modern Movements</h2>&#13; &#13; <p>The geologic forces that were active in the past are still active today. In the nineteenth century, tumbling rocks and <a href="https://coloradoencyclopedia.org/article/snow"><strong>snow</strong></a> often blocked or destroyed stretches of railroad track and hampered railroad construction. Modern Coloradans were grimly reminded of the state’s geologic hazards in May 2014, when a thick rock-and-debris <a href="/article/avalanche"><strong>avalanche</strong></a> tumbled down from a high mesa in western Colorado for nearly three miles at speeds between 45 and 85 miles per hour. Three men died in the avalanche, which occurred after a period of significant rainfall saturated sediments that had been deposited millions of years earlier. The sediments had been exposed by the downward-cutting streams and rivers that carved the modern valley the avalanche rushed into. Another reminder of the precarious interplay between geology and infrastructure occurred on February 15, 2016, when a rock slide in <strong>Glenwood Canyon</strong> in <a href="/article/garfield-county"><strong>Garfield County</strong></a> forced the closure of twenty-four miles of <a href="/article/interstate-70"><strong>Interstate 70</strong></a> for about a week.</p>&#13; &#13; <h2>Reflections</h2>&#13; &#13; <p>Crossing the plains into Colorado from its eastern neighbors, it is easy to imagine the land once being the bottom of an ancient sea. Looking north and south, where the peaks spike upward from the flatlands, the immense movement of mountains seems impossible, as do the threats of lightning-filled, ash-laden volcanic clouds from millions of years ago. Continuing westward through spectacular canyons, it is hard to fathom that a small shrug of a restless Earth could change the course of a river in a flash. But pause and try to envision the dynamic processes that shaped the land, and that checkered saga will come alive.</p>&#13; </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-author--encyclopedia-article.html.twig * field--node--field-author.html.twig x field--node--encyclopedia-article.html.twig * field--field-author.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-author field--type-entity-reference field--label-above" id="id-field-author"> <div class="field__label" id="id-field-author">Author</div> <div class='field__items'> <div class="field__item" id="id-field-author"><a href="/author/benson-robert" hreflang="und">Benson, Robert</a></div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-keyword--encyclopedia-article.html.twig * field--node--field-keyword.html.twig x field--node--encyclopedia-article.html.twig * field--field-keyword.html.twig * field--entity-reference.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-keyword field--type-entity-reference field--label-above" id="id-field-keyword"> <div class="field__label" id="id-field-keyword">Keywords</div> <div class='field__items'> <div class="field__item" id="id-field-keyword"><a href="/keyword/colorado-geology" hreflang="en">colorado geology</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/rocky-mountains" hreflang="en">Rocky Mountains</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/geology" hreflang="en">geology</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/formation-rocky-mountains" hreflang="en">formation of rocky mountains</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/fossils" hreflang="en">fossils</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/ore-deposits" hreflang="en">ore deposits</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/colorado-plateau" hreflang="en">colorado plateau</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/canyons" hreflang="en">canyons</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/grand-mesa" hreflang="en">grand mesa</a></div> <div class="field__item" id="id-field-keyword"><a href="/keyword/western-slope" hreflang="en">Western Slope</a></div> </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'links__node' --> <!-- FILE NAME SUGGESTIONS: * links--node.html.twig x links--inline.html.twig * links--node.html.twig * links.html.twig --> <!-- BEGIN OUTPUT from 'themes/contrib/bootstrap_barrio/templates/navigation/links--inline.html.twig' --> <!-- END OUTPUT from 'themes/contrib/bootstrap_barrio/templates/navigation/links--inline.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-references-html--encyclopedia-article.html.twig * field--node--field-references-html.html.twig x field--node--encyclopedia-article.html.twig * field--field-references-html.html.twig * field--text-long.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-references-html field--type-text-long field--label-above" id="id-field-references-html"> <div class="field__label" id="id-field-references-html">References</div> <div class="field__item" id="id-field-references-html"><p>Chuck Hickey, “<a href="https://kdvr.com/news/one-lane-of-both-decks-of-i-70-in-glenwood-canyon-reopens-after-rock-slide/">One Lane on Both Decks of I-70 in Glenwood Canyon Reopens After Rock Slide</a>,” KDVR, March 10, 2016.</p>&#13; &#13; <p>Michael N. Machette, Mary-Margaret Coates, and Margo L. Johnson, “<a href="https://pubs.usgs.gov/of/2007/1193/">2007 Rocky Mountain Section Friends of the Pleistocene Field Trip—Quaternary Geology of the San Luis Basin of Colorado and New Mexico, September 7–9</a>,”<em> US Geological Survey Open-File Report 2007-1193 </em>(September 2007).</p>&#13; &#13; <p>R. F. Madole, J. H. Romig, J. N. Aleinikoff, D. P. VanSistine, and E. Y. Yacob, “<a href="https://www.nps.gov/grsa/learn/nature/upload/madole_geology_article-2.pdf">On the Origin and Age of the Great Sand Dunes, Colorado</a>,” <em>Geomorphology</em> 99 (October 2008).</p>&#13; &#13; <p>Vincent Matthews: <em>Messages in Stone: Colorado’s Colorful Geology,</em> 2nd ed. (Denver: Colorado Geological Survey, 2009).</p>&#13; &#13; <p>Jonathan L. White, Matthew L. Morgan, Karen A. Berry, “<a href="https://coloradogeologicalsurvey.org/publications/west-salt-creek-landslide-catastrophic-rockslide-avalanche-mesa-colorado/">The West Salt Creek Landslide: A Catastrophic Rockslide and Rock/Debris Avalanche in Mesa County, Colorado</a>,” <em>Colorado Geological Survey Bulletin</em> 55 (2015).</p>&#13; </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <!-- THEME DEBUG --> <!-- THEME HOOK: 'field' --> <!-- FILE NAME SUGGESTIONS: * field--node--field-additional-information-htm--encyclopedia-article.html.twig * field--node--field-additional-information-htm.html.twig x field--node--encyclopedia-article.html.twig * field--field-additional-information-htm.html.twig * field--text-long.html.twig * field.html.twig --> <!-- BEGIN OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> <div class="field field--name-field-additional-information-htm field--type-text-long field--label-above" id="id-field-additional-information-htm"> <div class="field__label" id="id-field-additional-information-htm">Additional Information</div> <div class="field__item" id="id-field-additional-information-htm"><p>Andrew Alden, “<a href="https://www.thoughtco.com/geologic-maps-of-the-united-states-4122863">Colorado Geologic Map</a>,” About.com, updated March 27, 2016.</p>&#13; </div> </div> <!-- END OUTPUT from 'themes/custom/encyclopedia/templates/field/field--node--encyclopedia-article.html.twig' --> Fri, 24 Jun 2016 20:26:50 +0000 yongli 1503 at http://coloradoencyclopedia.org