Colorado’s geological history began many millions of years ago. Its many geologic features have played a major role in its human history. It started as a mountain range off the coast of the Wyoming Province sitting only 4-7 degrees north of the earth’s equator (Steiner) as part of the formation of the super continent called Pangaea. The features it has developed through the eons contribute to the state’s economy today.
Pangaea and the Ancestral Rocky Mountains
Colorado was still close to the equator at the end of the Paleozoic Era, 543-248 million years before the present (BP). The formation of Pangaea was completed by the end of the era and a time of mountain building began, with the collision of Northern and Southern continents that are now North America, South America and Africa. The mountain range that formed is known as the Ancestral Rocky Mountains.
The Denver Basin was formed as the heavy Ancestral Rockies caused the land in front of them to stretch. Sedimentary rocks from eroding mountains washed down, filling the basin. By the end of the Permian Period (290-248 million BP) the Ancestral Rockies were gone. Thick heavy sediments formed into sandstone, trapping the tropical plain life, creating kimberlite formations which contain diamonds.
Other evidence of this sediment is found in the uplifts that create such tourist attractions as the Garden of the Gods, Red Rocks Amphitheatre and Maroon Bells. Longs Peak, a 14,000 ft peak that attracts mountain climbers and tourists today, has a base that sits 12-13,000 feet below the soils of the Denver Basin, covered by this sediment. This makes the mountain twice its visible size.
Mesozoic Colorado (249-65 million BP)
Millions of years passed and the earth’s crust, moving on tectonic plates, pulled Pangaea apart. By the time of the Mesozoic Era, Colorado had drifted well north of the equator:
During the Triassic Period (250-200 million BP) the mountains were flat and the climate arid. Formations that attract tourists today were formed as sand blew making dunes that became sandstone and eroded to form the beautiful spires and pinnacles of the Colorado National Monument.
At the later part of the Jurassic Period (200-147 million BP), Colorado had reached its present location north of the equator and returned to a moist climate. The Morrison Formation west of Denver is a record of this period, containing fossilized plants and animals.
During the Cretaceous Period (145-65 million BP) oceans reappeared. Colorado was 600 feet below sea level. The sand and mud deposits left by these oceans crushed ocean plants under pressure, creating a low sulfur coal seam in southwestern Colorado. The Benton Formation in eastern Colorado also buried plants, creating natural gas and oil.
Birth of the Rocky Mountains
At the beginning of the Cretaceous period Colorado underwent another mountain building period known as the Laramide Orogeny, resulting in the present day Rocky Mountains. Volcanoes dotted the Rockies bringing gold, silver and other minerals closer to the surface. This mountain building continues today with a large dome rising under the Mineral Belt, running roughly along the continental divide. Gold and other mineral deposits from the Orogeny have contributed to the Colorado economy during historic times.
Alluvial fans, created by the erosion from the Rocky Mountains, filled a basin to the east of the Rockies with up to 200 meters of lightly compacted sand and clay forming one of the region’s most important geologic structures, the Ogallala aquifer. The aquifer supplies water to present day farms and metropolitan areas that could not exist without it.
Mountain parks, broad flat areas left behind by uplift, are also economic treasures. These plains are agricultural centers. The San Luis Valley is one such park created by the Rio Grande Rift.
End of Mesozoic and New Beginning for Colorado
The Mesozoic period drew to a close with the extinction of the dinosaurs and many other species. Colorado, which had had a thriving subtropical climate became a desert. Debris and volcanic ash cooled the climate. Polar ice caps formed and ice spread south into North America. Even areas not covered by the ice sheets had mountain glaciers and cold climates.
The climate changed again at the end of the Pleistocene Epoch, around 10,000 years ago. Grasslands covered the Colorado plains. Warm blooded animals, which could withstand the colder climates, appeared. Colorado’s history moved to a new stage. Its geology created an area that for eons has drawn humankind with its abundant natural resources, providing food, water and natural materials.
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Pangaea and the Ancestral Rocky Mountains
Colorado was still close to the equator at the end of the Paleozoic Era, 543-248 million years before the present (BP). The formation of Pangaea was completed by the end of the era and a time of mountain building began, with the collision of Northern and Southern continents that are now North America, South America and Africa. The mountain range that formed is known as the Ancestral Rocky Mountains.
The Denver Basin was formed as the heavy Ancestral Rockies caused the land in front of them to stretch. Sedimentary rocks from eroding mountains washed down, filling the basin. By the end of the Permian Period (290-248 million BP) the Ancestral Rockies were gone. Thick heavy sediments formed into sandstone, trapping the tropical plain life, creating kimberlite formations which contain diamonds.
Other evidence of this sediment is found in the uplifts that create such tourist attractions as the Garden of the Gods, Red Rocks Amphitheatre and Maroon Bells. Longs Peak, a 14,000 ft peak that attracts mountain climbers and tourists today, has a base that sits 12-13,000 feet below the soils of the Denver Basin, covered by this sediment. This makes the mountain twice its visible size.
Mesozoic Colorado (249-65 million BP)
Millions of years passed and the earth’s crust, moving on tectonic plates, pulled Pangaea apart. By the time of the Mesozoic Era, Colorado had drifted well north of the equator:
During the Triassic Period (250-200 million BP) the mountains were flat and the climate arid. Formations that attract tourists today were formed as sand blew making dunes that became sandstone and eroded to form the beautiful spires and pinnacles of the Colorado National Monument.
At the later part of the Jurassic Period (200-147 million BP), Colorado had reached its present location north of the equator and returned to a moist climate. The Morrison Formation west of Denver is a record of this period, containing fossilized plants and animals.
During the Cretaceous Period (145-65 million BP) oceans reappeared. Colorado was 600 feet below sea level. The sand and mud deposits left by these oceans crushed ocean plants under pressure, creating a low sulfur coal seam in southwestern Colorado. The Benton Formation in eastern Colorado also buried plants, creating natural gas and oil.
Birth of the Rocky Mountains
At the beginning of the Cretaceous period Colorado underwent another mountain building period known as the Laramide Orogeny, resulting in the present day Rocky Mountains. Volcanoes dotted the Rockies bringing gold, silver and other minerals closer to the surface. This mountain building continues today with a large dome rising under the Mineral Belt, running roughly along the continental divide. Gold and other mineral deposits from the Orogeny have contributed to the Colorado economy during historic times.
Alluvial fans, created by the erosion from the Rocky Mountains, filled a basin to the east of the Rockies with up to 200 meters of lightly compacted sand and clay forming one of the region’s most important geologic structures, the Ogallala aquifer. The aquifer supplies water to present day farms and metropolitan areas that could not exist without it.
Mountain parks, broad flat areas left behind by uplift, are also economic treasures. These plains are agricultural centers. The San Luis Valley is one such park created by the Rio Grande Rift.
End of Mesozoic and New Beginning for Colorado
The Mesozoic period drew to a close with the extinction of the dinosaurs and many other species. Colorado, which had had a thriving subtropical climate became a desert. Debris and volcanic ash cooled the climate. Polar ice caps formed and ice spread south into North America. Even areas not covered by the ice sheets had mountain glaciers and cold climates.
The climate changed again at the end of the Pleistocene Epoch, around 10,000 years ago. Grasslands covered the Colorado plains. Warm blooded animals, which could withstand the colder climates, appeared. Colorado’s history moved to a new stage. Its geology created an area that for eons has drawn humankind with its abundant natural resources, providing food, water and natural materials.
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