Geog 1520 assignment 12.docx

Geog 1520 assignment 12.docx - 1 200 million years ago...

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1. 200 million years ago, tectonic forces began moving the North American Plate westwards, it eventually collided with the Pacific Plate, and the force of the collision, called the Columbia Orogeny, moved east over North America, cracking enormous masses of rock and forcing the sedimentary layers up and over the adjacent land. This process created the main ranges of the western and central Rocky Mountains. A second collision, known as the Laramide Orogeny that ended about 35 to 55 million years ago, created the foothills and the front ranges of the Rocky Mountains. This was also a time of volcanic activity in the Rocky Mountains, but eventually the volcanic activity ceased and the magma cooled, leaving craterlike formations called calderas. In the millennia that followed, water flow carried sediment from high in the mountains into the valleys and plains below, creating v-shaped valleys like Hell’s canyon at 7800 feet, which was shaped by the Snake River. Many of the features of the mountainous west were created
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  • Spring '14
  • EricC.Ewert
  • Rocky Mountains

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