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Our Glaciers: Then and Now activity kit helps you see the changes taking place in glaciers around the world. See all our activity kits and classroom activities.
This photograph of Kelvin-Helmholtz clouds was taken in the foothills of the Rocky Mountains.
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Courtesy of Benjamin Foster/UCAR

Kelvin-Helmholtz

Kelvin-Helmholtz clouds look like breaking waves in the ocean. When wind blows up and over a landform, like a mountain, the air continues flowing in a pattern that looks like a wave.

Last modified November 30, 2007 by Becca Hatheway.

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The Fall 2009 issue of The Earth Scientist, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store.

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Altocumulus

Altocumulus clouds are part of the Middle Cloud group. They are grayish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups. Altocumulus clouds are about...more

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Altostratus clouds belong to the Middle Cloud group. An altostratus cloud usually covers the whole sky. The cloud looks gray or blue-gray. The sun or moon may shine through an altostratus cloud, but will...more

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