What types of erosion help create V-shaped valleys?

V-shaped valley
As the river erodes downwards the sides of the valley are exposed to freeze-thaw weathering which loosens the rocks (some of which will fall into the river) and steepens the valley sides. The rocks which have fallen into the river help the process of corrasion and this leads to further erosion.

If you get a map and put the countries a states all together it forms all one piece you can also tell because of the earth quakes