Physics Photo of the Week

November 2, 2012

Glaciation Evidence
In Denali National Park, Alaska, there are many active glaciers as well as glaciers that have shaped the landscape only a few thousand years ago.  The long mound in the center of this photo is a glacial lateral moraine.  A lateral moraine is a long pile of debris - mostly small rocks - that has been deposited at the edge of a moving glacier.  This glacier has obviously receded leaving the piles of rubble-like rock as evidence.  Many parts of the northern US show characteristic glacial moraines - piles of rocks of all sizes - as evidence of glacial activity.

The next picture is the active Matanuska Glacier near Anchorage.  On the far side of the Matanuska glacier we see a lateral moraine - very similar to the top photo.  Glaciers act as "conveyor belts", not as "bulldozers", in spreading rock debris.  Rocks and boulders fall onto the glaciers from the valley walls and are then transported to the terminus and areas where the glacier becomes thinner, thus leaving the carried rocks and debris either at the terminus or the side.  The bottom part of the valley in the foreground is still part of the glacier - it is completely covered with dirt and debris.  As the glacier melts in the approach toward the terminus, the rocks and debris become more concentrated on the surface.  There are parts of the Matanuska glacier that are forested with trees!

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to dcollins@warren-wilson.edu.

All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion.  These photos and discussions may be used for private individual use or educational use.  Any commercial use without written permission of the photoprovider is forbidden.

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