The James River Park System - Richmond, VA

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South Geology Tour

Stop 6: Mother Nature's Curves

DIRECTIONS: Walk to the middle of the river bed. Look to your left at the large rock mass. Note that the edges are  rounded. (37.526240° N, 077.454791° W)

Rocks are shaped in two ways. Look to your left  to see the sculpting by Mother Nature.

Curves in rocks

Rounded shapes occur from WEATHERING.

ABRASION is a process by which sediments grind down rough edges during flood events.

SPHEROIDAL WEATHERING is a process by which granite breaks down most rapidly at corners, less rapidly at edges, and slowest at the center of the faces of the block. This process occurs most rapidly at the corners, causing the rounded edges you see.

Weathering in rocks

EXFOLIATION lines of stress are created in layers as overlying rock weathers away and the underlying granite expands. These lines are points of weakness along which the  granite tends to break. These surfaces can be millimeters to meters thick.

Exfoliation cracks

Notice how these layers of rock are peeling off from the layers beneath, making it easier to remove the rock.

Example of exfoliation

This rock is a good example of EXFOLIATION.

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