Large natural rock cavity along with many smaller ones seen here are the result of fractures and erosion that continues even today in Quebec Eastern Townships forested mountains.
This scene is from last November 2017, in woods not very far from cottage, after a light dusting of snow, the start of this year’s hard winter.
The hard grey rock ledge shows a lot of cavitation and fracture common in this area which experienced the last ice age when massive glaciers scraped and sliced the area while receding after temperatures rose additionally, there was natural erosion caused by winds and abrasive dust.
Furthermore, vegetation primarily trees have contributed to even more to the transformation when their root systems invade the cracks and cavities expanding them and allowing water from rains in to accumulate inside and freeze into ice in winter rupturing rock even more.
This is my contribution for WP single word prompt:”CAVITY”.