Landforms of glacial erosion - Crag and tail Flashcards
How is a crag and tail formed?
They’re formed when a glacier or ice sheet passes over an area that contains a particular resistant rock formation
What do erosional crag-and-tails consist of? ?
Erosional crag-and-tails consist of a highly resistant rock (crag) that protected less resistant rock (tail) from the full force of glacial erosion.
What type of rock surrounds a crag and tail?
Loose glacial till
On a crag and tail why is one side smooth and another side rough?
.The rough side is hard rock and there is more resistant so the gravel doesn’t make as noticeable of a difference
.The smooth side of the rock is the loose gravel, this has been smoothed out and flattened as the glacier has moved over the top of it
What has the crag resisted?
The crag has resisted glacial erosion and forms an obstruction to the ice, producing a ‘pressure shadow’ in its lee.
Describe the pressure shadow that is produced by the crag in its lee?
The pressure shadow extends in a down-ice direction in proportion to the ice velocity and thickness and creates a gradually tapering zone of minimal erosion. This is a good example of differential erosion.
What is differential erosion?
Differential erosion is erosion that occurs at varying rates, caused by the differences in the resistance and hardness of surface materials. Softer and weaker rocks are rapidly worn away, whereas harder and more resistant rocks remain to form ridges, hills or mountains.
