in terms of a glacier, it is a similar principal; the moving of rocks over a surface wears it away with friction, digging a channel that, when the glacier moves away, is called a u-shaped valley. short treatment time - a typical treatment takes less than 5 minutes. even in doing this, the seeds may not germinate. ), see the articles for those races. this is to give the illusion of height. he started the competition at the second round. they screwed shut and could hinge open to completely release the rope. 