The promontory at Stony Ledge looking down into the Hopper, showing the Greylock Schist

The backbone of the mountain was formed from the remnants of an ancient sea bed. According to geologists, between 600 to 450 million years ago, the older Greylock Schist and quartzite formations of mountain are believed to have been thrust up and folded over on top of the younger limestone and marble of the Hoosac Valley to the east. At one time reaching perhaps 20,000 feet in height, the Greylock massif has been reduced to its present size over eons by constant erosion, a process that still continues, and on the rare occasion in the form of a landslide.

Mammals that can be found on Greylock include moose, white-tailed deer, black bear more...