process: ventifaction location: mc murdo dry valley prevailing winter wind direction: westerly off...

Process: Ventifaction

Location: Mc Murdo Dry Valley

Prevailing winter wind direction: Westerly off Ice Sheet

Dry Valley conditions favour process of ventifaction:

• Desert conditions (lack of precipitation)

• No snow cover and little vegetation, so … plentiful supply of exposed particles of rock and ice

• Frequent strong katabatic (gravity driven) winds.

Ventifact rock - often weird and wonderful

shapes

Loose, exposed rock and snow particles

Abrasion erosion: wind carried particles are ‘sand blasted’ against facing rock surface

Katabatic (gravity driven) winds carrying rock and snow particles

(eolian transport)

Even in strong winds, particles can’t be continuously held in the air. Instead, particles bounce along ground - saltation.

This erosion is focused on base of ventifact, resulting in mushroom shaped rocks

Side of rock facing prevailing wind may become grooved or polished

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