Answer:
a huge depression
Step-by-step explanation:
Mesa Verde is a place geologically famous for the 'alcove formation'. These alcoves are the depressions formed when water goes into the cracks, it gets freezed and due to freezing it exerts pressure on the surrounding, causing surrounding walls/rocks to move away or apart from each other. This the alcoves are formed. They are depressions similar to caves, but caves are formed underground.