Geology (Mt. Evans)
Title: Mt. Evans Geology
Entered by: BillMiddlebrook
Added: 05/03/2010, Last Updated: 05/03/2010
Sources: Halka Chronic, Roadside Geology of Colorado (Mountain Press Publishing, 1980)
Formed about 1.7 billion years ago, during Precambrian time, Mt. Evans rock is composed of granite that pushed up through metamorphic rocks as an extrusion of magma. Slow cooling of the rock provided for easy identification of minerals like white and pink feldspar, glassy quartz and black mica. As part of the Ancestral Rockies (300 million years ago), the granite was pushed upward and again 65 million years ago during the Laramide Orogeny.
Over the years since the general mountain formation, the rock has cracked and weathered. The weathering process has rounded the boulders as the mica grains break down and cause portions of the rock (often quartz and feldspar) to break off. Wind-blasting has also taken a toll on windward facing rock, above tree line.
The Summit Lake area was formed by glacier activity which created a large, east-facing cirque between Mt. Evans and 13er Mt. Spalding.