Geology of 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.
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 the Laramie Mountains.
Both the anorthosite and granite transect the Cheyenne belt in the Laramide Mountains, and intrude crystalline rocks of the Wyoming province.
These deep extensional basement faults filled with sediments, such as the Uinta rift basin and were reactivated more recently in Earth history by orogenies.
[citation needed] The end of 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.
[6] During the Paleozoic, western North America lay underneath a shallow sea, which deposited many kilometers of limestone and dolomite.
They consisted largely of Precambrian metamorphic rock, forced upward through layers of the limestone laid down in the shallow sea.
[8]: 6 Mesozoic deposition in the Rockies occurred in a mix of marine, transitional, and continental environments as local relative sea levels changed.
[10] Terranes started to collide with the western edge of North America in the Mississippian age (approximately 350 million years ago), causing the Antler orogeny.
[11] 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 the effects of repeated collision as the Kula and Farallon Plates sank beneath the continental edge.
Great arc-shaped volcanic mountain ranges, known as the Sierran Arc, grew as lava and ash spewed out of dozens of individual volcanoes.
[12] It is postulated that the shallow angle of the subducting plate greatly increased the friction and other interactions with 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.
