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44-692: The Kenosha Mountains or Kenosha Mountain are a subrange (or long mountain) of the Front Range located in Park and Jefferson counties of Colorado. Lying within the Pike National Forest , the range extends 36 miles (58 km) from where it meets the Platte River Mountains to the northwest, to Windy Peak to the southeast. This long mountain is bordered by the Platte River Mountains on

88-473: A fairly steep angle, and a volcanic arc grows above the subducting plate. During the growth of the Rocky Mountains, the angle of the subducting plate may have been significantly flattened , moving the focus of melting and mountain building much farther inland than is normally expected. It is postulated that the shallow angle of the subducting plate greatly increased the friction and other interactions with

132-580: A hardwood floor: the rug bunches up and forms wrinkles (mountains). In Canada, the subduction of the Kula plate and the terranes smashing into the continent are the feet pushing the rug, the ancestral rocks are the rug, and the Canadian Shield in the middle of the continent is the hardwood floor. Farther south, the growth of the Rocky Mountains in the United States is a geological puzzle. Mountain building

176-524: A mountain system that stretches from Northern British Columbia through central New Mexico and which is part of the great mountain system known as the North American Cordillera . The rocky cores of the mountain ranges are, in most places, formed of pieces of continental crust that are over one billion years old. In the south, an older mountain range was formed 300 million years ago, then eroded away. The rocks of that older range were reformed into

220-642: A ridge between the mountains and the plains. Over the next 35 million years, the Cretaceous seaway repeatedly widened as far as Utah and Wisconsin and narrowed to near closure. With no mountains present at the time, the Colorado area was in the line of the deepest channel of the seaway; but being on the Transcontinental Arch , the Front Range areas was relatively shallow and was near the last land to submerge as

264-519: Is normally focused between 200 and 400 miles (300 and 600 km) inland from a subduction zone boundary. Geologists continue to gather evidence to explain the rise of the Rockies so much farther inland; the answer most likely lies with the unusual subduction of the Farallon plate , or possibly due to the subduction of an oceanic plateau . At a typical subduction zone, an oceanic plate typically sinks at

308-519: The Ancestral Rockies were eroding away while the shoreline was present during the break-up of Pangaea. This formation began right after Earth's largest extinction 251 million years ago at the Permian – Triassic Boundary. Ninety percent of the planet's marine life became extinct and a great deal on land as well. After 100 million years of deposition, a new environment brought rise to a new formation,

352-797: The Bull Lake Glaciation that began about 150,000 years ago and the Pinedale Glaciation that probably remained at full glaciation until 15,000–20,000 years ago. Ninety percent of Yellowstone National Park was covered by ice during the Pinedale Glaciation. The little ice age was a period of glacial advance that lasted a few centuries from about 1550 to 1860. For example, the Agassiz and Jackson Glaciers in Glacier National Park reached their most forward positions about 1860 during

396-725: The Cretaceous period when the western part of the Western Interior Seaway covered the region. Terranes started to collide with the western edge of North America in the Mississippian age (approximately 350 million years ago), causing the Antler orogeny . During the last half of the Mesozoic Era , much of today's California , British Columbia , Oregon , and Washington were added to North America . Western North America suffered

440-510: The Denver and Salt Lake Railway , the former Rio Grande is used for freight by both Union Pacific and BNSF , and it is also used by Amtrak 's California Zephyr and Winter Park Express . Ancestral Rockies The geology of the Rocky Mountains is that of a discontinuous series of mountain ranges with distinct geological origins. Collectively these make up the Rocky Mountains ,

484-500: The Interstate 25 corridor. The area is a popular destination for mountain biking, hiking, climbing, and camping during the warmer months and for skiing and snowboarding during winter. Millions of years ago, the present-day Front Range was home to ancient mountain ranges, deserts, beaches, and even oceans. The name "Front Range" is also applied to the Front Range urban corridor , the populated region of Colorado and Wyoming just east of

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528-708: The Laramie Mountains . The Colorado orogeny was likely part of the larger Yavapai orogeny , which extended across North America and probably to other continents that were joined to North America as part of the supercontinent , Columbia . In the Paleoproterozoic, terranes also accumulated on the west side of the Wyoming Craton, forming the Selway terrane in Idaho. Mesoproterozoic (~1.4 Ga) anorthosite and syenites of

572-658: The Little Ice Age . All of the geological processes, above, have left a complex set of rocks exposed at the surface. For example, in the Rockies of Colorado, there is extensive granite and gneiss dating back to the Ancestral Rockies. In the central Canadian Rockies, the main ranges are composed of the Precambrian mudstones , while the front ranges are composed of the Paleozoic limestones and dolomites. Volcanic rock from

616-607: The Paleoproterozoic , island-arc terrane associated with the Colorado orogeny accreted to the Wyoming Craton along the Cheyenne belt , a 500-km-wide belt of Proterozoic rocks named for Cheyenne, Wyoming . As a result of the collision, older, Archean rocks of the Wyoming craton were intensely deformed and metamorphosed for at least 75 km inboard from the suture, which is marked today by

660-600: The continental margin while others represent small isolated mid-oceanic islands. Magma generated above the subducting slab rose into the North American continental crust about 200 to 300 miles (300 to 500 km) inland. Great arc-shaped volcanic mountain ranges, known as the Sierran Arc , grew as lava and ash spewed out of dozens of individual volcanoes . Beneath the surface, great masses of molten rock were injected and hardened in place. For 270 million years,

704-557: The limestone laid down in the shallow sea. The mountains eroded throughout the late Paleozoic and early Mesozoic , leaving extensive deposits of sedimentary rock . Mesozoic deposition in the Rockies occurred in a mix of marine, transitional, and continental environments as local relative sea levels changed. By the close of the Mesozoic , 10,000 to 15,000 feet (3000 to 4500 m) of sediment accumulated in 15 recognized formations . The most extensive non-marine formations were deposited in

748-636: The Colorado orogen. The breakup of the Rodinia supercontinent produced rifts between 900 million and 600 million years ago in the Neoproterozoic . These deep extensional basement faults filled with sediments, such as the Uinta rift basin and were reactivated more recently in Earth history by orogenies. The Uinta Formation and Uncompahgre Formation are both examples of remnant Precambrian rift basin sediments. The end of

792-425: The Front Range are Interstate 70 , which crosses west of Denver, Colorado, and Interstate 80 , which crosses near Laramie, Wyoming. U.S. Route 34 travels through the mountains near Loveland, Colorado , although this route is typically closed from October to May. U.S. Route 24 travels through the southern Front Range west of Colorado Springs , eventually connecting with I-70 west of Vail, Colorado . Along with

836-489: The Front Range. Eventually, at about 10 million years ago, the Front Range began to rise up again and the resistant granite in the heart of the mountains thrust upwards and stood tall, while the weaker sediments deposited above it eroded away. As the Front Range rose, streams and recent (16,000 years ago) glaciations during the Quaternary age literally unburied the range by cutting through the weaker sediment and giving rise to

880-631: The Laramie Anorthosite Complex and granite intrude into rocks of the Colorado orogen in the Laramie and adjacent Medicine Bow Mountains . Both the anorthosite and granite transect the Cheyenne belt in the Laramide Mountains, and intrude crystalline rocks of the Wyoming province. These intrusions comprise the northernmost segment of a wide belt of 1.4 Ga granitic intrusions that occur throughout

924-591: The Neoproterozoic is not known from the rock record, indicating a period of long-running terrestrial erosion which produced by the Great Unconformity , from 1.1 billion to 510 million years ago. Twelve to 24 kilometers of basement rock eroded away. During the Paleozoic , western North America lay underneath a shallow sea, which deposited many kilometers of limestone and dolomite . In the southern Rocky Mountains, near present-day Colorado and New Mexico ,

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968-667: The Precambrian and Paleozoic rocks were disturbed by mountain building approximately 300 Ma, during the Pennsylvanian . This mountain building produced the Ancestral Rocky Mountains . The uplift formed two large mountainous islands, known to geologists as Frontrangia and Uncompahgria , located roughly in the current locations of the Front Range and the San Juan Mountains . They consisted largely of Precambrian metamorphic rock , forced upward through layers of

1012-627: The Rocky Mountains were formed before the mountains were raised by tectonic forces. The oldest rock is Precambrian Wyoming craton that forms the core of the North American continent. The Wyoming Craton originated as a 100,000 km middle Archean craton that was modified by late Archean volcanic magmatism and plate movements and Proterozoic extension and rifting . The Wyoming Craton mainly consists of two rock units: granitoid plutons (2.8–2.55 Ga) and gneiss and migmatite . The granitoid rocks are mainly potassic granite and were derived principally from reworked older (3.1–2.8 Ga) gneiss. During

1056-419: The Rocky Mountains. The Rocky Mountains took shape during an intense period of plate tectonic activity that resulted in much of the rugged landscape of western North America . The Laramide orogeny , about 80–55 million years ago, was the last of the three episodes and was responsible for raising the Rocky Mountains. Subsequent erosion by glaciers has produced the current form of the mountains. The rocks in

1100-466: The earth as it recovered from this tremendous disaster. The uplifted mountains continued to constantly erode and, by 40 million years ago, the region was once again buried in material eroded from the central mountains. Suddenly, 37 million years ago, a great volcanic eruption took place in the Collegiate Range and covered the landscape in hot ash that instantly torched and consumed everything across

1144-729: The east slope of the Dakota Hogback. The non-chalky shales of the Pierre Formation formed in the final cycle of the seaway. At about 68 million years ago, the Front Range began to rise again due to the Laramide Orogeny in the western half of the state, draining from being at the bottom of a sea to land again, giving yield to another fossiliferous rock layer, the Denver Formation. The Denver Formation contains fossils of dinosaurs like Tyrannosaurus rex and Triceratops . While

1188-633: The effects of plate collisions were focused very near the edge of the North American Plate boundary, far to the west of the Rocky Mountain region. It was not until 80 MA that these effects began to reach the Rockies. The current Rocky Mountains were raised in the Laramide orogeny from between 80 and 55 Ma. For the Canadian Rockies, the mountain building is analogous to a rug being pushed on

1232-508: The effects of repeated collision as the Kula and Farallon Plates sank beneath the continental edge. Slivers of continental crust, carried along by subducting ocean plates, were swept into the subduction zone and scraped onto North America's western edge. These terranes represent a variety of tectonic environments. Some are ancient island arcs, similar to Japan, Indonesia and the Aleutians; others are fragments of oceanic crust obducted onto

1276-561: The forests of vegetation, dinosaurs, and other organisms thrived, their reign would come to an end at the Cretaceous–Paleogene boundary (which was formerly known as the K-T boundary). In an instant, millions of species were obliterated by a meteor impact in Mexico's Yucatán Peninsula . While this extinction led to the demise of the dinosaurs and other organisms, some life did prevail to repopulate

1320-486: The granite eroded with no sedimentation forming over this first uplift, resulting in a local expression of the Great Unconformity . At about 500–300 million years ago, the region began to sink and sediments began to deposit in the newly formed accommodation space. Eroded granite produced sand particles that began to form strata, layers of sediment, in the sinking basin. Sedimentation would continue to take place until about 300 million years ago. Around 300 million years ago,

1364-450: The granitic peaks present today. This was the last step in forming the present-day geologic sequence and history of today's Front Range. The Front Range includes the highest peaks along the eastern edge of the Rockies. The highest mountain peak in the Front Range is Grays Peak . Other notable mountains include Torreys Peak , Mount Blue Sky , Longs Peak , Pikes Peak , and Mount Bierstadt . The main interstate highways that run through

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1408-557: The high rocks, revealing the ancestral rocks beneath, and forming the current landscape of the Rockies. Multiple periods of glaciation occurred during the Pleistocene Epoch (1.8 million–12,000 years ago), finally receding in the Holocene Epoch (fewer than 11,000 years ago). The ice ages left their mark on the Rockies, forming extensive glacial landforms, such as U-shaped valleys and cirques . Recent glacial episodes included

1452-491: The landscape. An entire lush environment was capped in a matter of minutes with 20 feet of extremely resistant rock, rhyolite . However, as seen before, life rebounds, and after a few million years mass floods cut through the rhyolite and eroded much of it as plants and animals began to recolonize the landscape. The mass flooding and erosion of the volcanic rock formed the Castle Rock Conglomerate that can be found in

1496-534: The modern range; they are now visible in many places throughout the Rockies, and are prominently shown along the Dakota Hogback , an early Cretaceous sandstone formation that runs along the eastern flank of the modern Rockies. Immediately after the Laramide orogeny, the Rockies were like Tibet : a high plateau, probably 6,000 metres (20,000 ft) above sea level. In the last 60 million years, erosion stripped away

1540-492: The mountain range and extending from Cheyenne, Wyoming south to Pueblo, Colorado . This urban corridor benefits from the weather-moderating effect of the Front Range mountains, which help block prevailing storms. About 1 billion years ago, a mass of magma rose to the surface through a much older mantle, cooling to form what is now known as the Precambrian Pikes Peak Granite . Over the next 500 million years,

1584-517: The north and the Tarryall Mountains on the south. This Colorado state location article is a stub . You can help Misplaced Pages by expanding it . Front Range The Front Range runs north-south between Casper, Wyoming , and Pueblo, Colorado , and rises nearly 10,000 feet above the Great Plains. Longs Peak , Mount Blue Sky , and Pikes Peak are its most prominent peaks, visible from

1628-522: The roads that run through the Front Range, the Union Pacific Railroad operates two rail lines through the mountains. The first Overland Route , transiting southern Wyoming, runs parallel to I-80 for much of its way. The second is the former Denver & Rio Grande Western Railroad Moffat Route, which runs parallel to the Colorado River and through the 6.5-mile-long Moffat Tunnel . Originally

1672-511: The sandstone Morrison Formation . The Morrison Formation contains some of the best fossils of the Late Jurassic . It is especially known for its sauropod tracks and sauropod bones, among other dinosaur fossils. As identified by the fossil record, the environment was filled with various types of vegetation such as ferns and Zamites . While this time period boasts many types of plants, grass had not yet evolved. The Dakota Sandstone , which

1716-612: The seaway opened. Shale and chalk were deposited over the area as Greenhorn of the Benton Group and the Niobrara Formation . Within these beds are found abundant marine fossils ( ammonites and skeletons of fish and such marine reptiles as mosasaurs , plesiosaurs , and extinct species of sea turtles ) along with rare dinosaur and bird remains. Today, the Fort Hays Limestone member forms flatirons or secondary hogbacks on

1760-462: The sinking suddenly reversed, and the sediment-covered granite began to uplift , giving rise to the Ancestral Rocky Mountains . Over the next 150 million years, during the uplift the mountains continued to erode and cover their flanks in their own sediment. Wind, gravity, rainwater, snow, and ice-melt supplied rivers that ultimately carved through the granite mountains and eventually led to their complete removal. The sediment from these mountains lies in

1804-651: The strata making up the section. Uplifted beds of Lyons Sandstone are found along the Front range and form the gateway to the Garden of the Gods . 30 million years later, the sediment deposition was still taking place with the introduction of the Lykins Shale . This formation can be best attributed to its wavy layers of muddy limestone and signs of stromatolites that thrived in a tidal flat in present-day Colorado. 250 million years ago,

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1848-471: The thick continental mass above it. Tremendous thrusts piled sheets of crust on top of each other, building the extraordinarily broad, high Rocky Mountain range. The current southern Rockies were forced upwards through the layers of Pennsylvanian and Permian sedimentary remnants of the Ancestral Rocky Mountains. Such sedimentary remnants were often tilted at steep angles along the flanks of

1892-644: The very red Fountain Formation today. Red Rocks Amphitheatre outside of Denver, Colorado, is set within the Fountain Formation. At 280 million years ago, sea levels were low and present-day Colorado was part of the super-continent Pangaea . Sand deserts covered most of the area, spreading as dunes seen in the rock record, known today as the Lyons Sandstone . These dunes appear to be cross-bedded and show various fossil footprints and leaf imprints in many of

1936-582: Was deposited around 100 million years ago at the opening of the Cretaceous Western Interior Seaway from the Arctic to the Tropics, shows evidence of ferns and dinosaur tracks. Sheets of ripple marks can be seen on some of the strata, confirming advancing and retreating near-shore environments. These Dakota Group sandstone beds are resistant to erosion and have uplifted to form the Dakota Hogback ,

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