Mountain Features



bute
The feature at the left is called a butte. Conditions for butte formation start with a hard rock lying on top of softer rock. The softer rock erodes quickly but the hard rock that forms the top of the butte helps to protect the softer rock underneath. When the hard top rock is eroded away there is no protection for the softer rock below so the quick erosion of the softer rock leaves a steep sided cliff that is relatively flat on top.
The mountain at the right, Mt. Shavano in  Colorado is an example of a glaciated mountain.  Two valleys in this mountain system show the characteristic U shape of glaciated valleys in comparison to the much steeper V shape valley of the Black Canyon. This is because the much more rigid ice erodes off sharp bends as it flows down the valley.

The sharp ridge in the middle of the two valleys is called an arete (internet fonts do not allow the ^ shape over the first e in arete).

At the top or head of the valley there is a cirque. Sometimes cirques get filled with water like the one below right. This lake is called a tarn. When 3 sides of a mountain are eroded away by glaciers the remaining point at the top is called a horn.

A col is formed when two valleys from opposite sides of the mountain run into each other forming what some call a "pass" over the mountain range.
mountain
mountain tarn
 


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