All the crumbly-looking layers in the gorge wall are shale. It was once se-bottom mud or clay. It is weak and easily destroyed by the action of water, freezing and other forces. As shale crumbles it often undermines a tougher layer above, leaving an overhanging ledge. In this way waterfalls commonly undermine themselves and gradually recede upstream.
Streams naturally attempt to assume a snake-like course called meandering.
Erosion of the bank is greater on the outside of a curve or meander. The cliff opposite is being undercut by the stream during high water and stones that fall from above are swept away. The grove on this side is within the inside of the meander. Floods rarely touch it. Rocks and soil that have fallen from above have accumulated and trees have been able to grow.