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.
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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