A rare cloud formation, called Kelvin-Helmholz waves, glides across the Victorian Alps, Australia. Kelvin-Helmholz waves are formed as two layers of air with different densities move past each other at different speeds. Just like ocean waves, the crests of Kelvin-Helmholz waves will crash as the air layer on top moves faster than the air layer on the bottom.

Photograph by Mark Pendavingh, My Shot
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cloud Encyclopedic Entry

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5 - 12 and up

Earth Science, Geography

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Clouds are visible accumulations of tiny water droplets or ice crystals in the Earth’s atmosphere