Upper Reaches of a Cirque

August 19, 2011


: Marli Bryant Miller; Marli's Web site
Summary Author: Marli Bryant Miller

Rocky Mountain National Park in Colorado contains many U-shaped glacial valleys, each of which ends at bowl-shaped region called a cirque. Cirques are the locations where glaciers accumulate most of their snow and ice, and so are the starting points for most glacial ice. Glacial erosion tends to create steep headwalls that frame in the cirque. The photo above shows the upper reaches of Glacier Gorge, which contains two cirques that merge downwards into one. The small peak (Spearhead) near the center of the photo forms a feature called an arete, as it separates the smaller cirques. From left to right, the larger peaks are Longs (14,256 ft or 4,345 m), Pagoda (13,497 ft or 4,113 m), and Chiefs Head (13,579 ft or 4,139 m), three of the four highest peaks in the national park. In the lower left corner, a hiker is perched on an outcrop of  Proterozoic granite, directly in front of Longs Peak. The bedrock in this area consists almost entirely of the same granite, although a large body of Proterozoic gneiss underlies the castellated ridge between Longs and Pagoda peaks. Photo taken July 16, 2011.

Photo details: Camera Maker: Canon; Camera Model: Canon EOS 5D Mark II; Lens: EF24-105mm f/4L IS USM; Focal Length: 24.0mm; Aperture: f/11.0; Exposure Time: 0.0040 s (1/250); ISO equiv: 100; Exposure Bias: none; Metering Mode: Spot; Exposure: program (Auto); White Balance: Manual; Flash Fired: No (enforced);
Orientation: Normal; Color Space: Adobe RGB (1998).