Crescent lake

This spectacular panorama was taken in Lake Clark National Park in southern Alaska.

The rocks in the foreground are part of the Chigmit Mountains. These rocks are mostly granitic and formed out to sea in the Jurassic as the base of a mountain range. The rocks solidified as part of a batholith, a huge body of mostly igneous rock formed as batches of magma moved through the crust one after another. That slice of crust eventually was carried north along with the moving oceanic plates and slammed into what is today Alaska, where we now refer to it as the Peninsular Terrane.

The high peak in the distance is Mount Redoubt, an active volcano built above the modern Aleutian Subduction Zone today. Redoubt’s last eruption sequence occurred in 2009, and it is expected to remain a major volcanic hazard in the future. Mount Redoubt is over 3100 meters high and is the highest peak in the Aleutian Range.

The valley in the foreground holding Crescent Lake is a classic glacially carved valley, as shown by the general U-shape of the valley (which is being flattened out progressively as sediments move into the lake).

-JBB

Image credit: NPS http://bit.ly/29Hha1W