Saturday, March 06, 2010
This rock in Squantum was formed about 6 billion years ago and sculpted by the Wisconsin glacier which moved across the South Shore about 15,000 years ago. The oldest of the rocks at the base of the rocky formation are basalt, gneiss and an early granite; on top is a crumbly rock called tillite. You can really see the mixture of colored pebbles held together in a fine matrix in the second image.
Geologists and others have long been fascinated by Squantum's interesting geology. It's hard to fathom this land covered by giant sheets of mud first and then ice, both more than 100 feet thick.
John Adams wrote about this place on October 22nd, 1762: "The rocks seem to be a vast collection of pebbles as big as hens eggs, thrown into melted cement and cooled in. You may pull them to pieces with your fingers, as fast as you please."