Lost River Mountains

by Robert Bales

Title

Lost River Mountains

Artist

Robert Bales

Medium

Photograph - Photo

Description

The Lost River Range is a group of high mountains located in central Idaho, in the northwestern United States. It runs southeast for approximately 75 miles (121 km) from the Salmon River near the community of Challis to the Snake River Valley near Arco. To the west are the valleys of the Salmon and the Big Lost Rivers, while to the east are the Little Lost River and Pashimeroi Valleys.
The range starts at the east bank of the Salmon River, at an elevation of about 5,000 feet (1,500 m). It quickly rises to Grouse Creek Mountain (11,085 ft, 3378 m) and Dickey Peak (11,141 ft, 3395 m), and then descends to Double Springs Pass, location of one of just two roads to cross the range. Nearby is an interpretive site explaining the effects of the magnitude 6.9 Borah Peak Earthquake that hit the range on October 28, 1983. The Big Lost River Valley fell and the Lost River Range rose, leaving a fault scarp of up to 14 ft (4.3 m) along the base of the mountains.


The Lost River range, a fault block mountain range, has incredible vertical relief on the west side. A slightly less steep east side finds foothills, a small number of alpine lakes and several permanent streams.

The range is made up of folded Proterozoic and Paleozoic sedimentary rocks. The Lost River fault runs along the base of the mountains, and has been active over the last few million years. Huge alluvial fans radiate from the steep canyons and spread out over the valley.

Much of the northern end of the range, towards Challis, is covered with "Challis" volcanic rocks, making them very colorful.

Uploaded

August 18th, 2014

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