Mud Cracks

By William T. Hathaway

Mud Cracks

The White Oak Mountain Range within Pittsylvania County is composed of sedimentary rocks (although mostly indurated) that are made up mostly of sandstones, siltstones, shale, and conglomerates. Scattered throughout the sediments are dikes of igneous diabasic rocks which are considered younger formations due to their intrusive penetration into the older sedimentary formations. To geologists these particular sedimentary deposits are known as The Triassic Formations or Triassic Basin (indicating the presence of a prehistoric lake).

Since the Triassic Period is considered to have existed from 248 to 206 million years ago, students are fascinated when they run across specimens of well preserved mud cracks which are found at a few locations in the county. Present-day mud cracks are formed when the soft wet mud dries out quickly — imagine finding evidence of such a situation's having taken place millions of years ago!


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