German to English Science Geology Glaciers

Unter den Firsten der Gebirgskämme trifft man steilwandig in die Hänge eingelassene Felskessel, die einen flachen, oft von einem See bedeckten Boden haben und eine Schwelle aus ausgelagertem Schutt.

This is what I have for this sentence so far:
Under the mountain ridges you can find eroded hollows inserted vertically into the overhangs that have a flat floor which is often covered by a lake and cusp of deposited debris.

All assistance gratefully accepted. It's a book on cruising along the Norwegian coast.