The James River Park System - Richmond, VA

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North Geology Tour

Stop 7b: What a Flake

DIRECTIONS: Look across the river for rocks that appear to have layers and wrinkles. They are undergoing a weathering process called EXFOLIATION.

exfoliation

How does EXFOLIATION occur?
Granite is formed far underground and rocks that lie above the granite are heavy and act as compressors. As the James River carved down into the river valley, the pressure from above was reduced, and the granite underneath expanded into sheet-like rock, formed like an onion.

The layers look like ridges in the bedrock and can be millimeters to meters thick.

When the first block of rock is cut and removed from a mass of granite, it cannot be put back the next day because the underlying rock expands a little in response to the void.


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