The Explosive Origins of Pilot Knob


Leon Long examines the crystal structure of a volcanic rock sample he had previously collected from the Pilot Knob area. Sarah Beal photo

By Patrick Beach 

Not far from Austin-Bergstrom International Airport and McKinney Falls State Park, a mound rises on the landscape, maybe 150 feet above the flatter land surrounding it in southeastern Travis County. It is called Pilot Knob, and it doesn’t look like much.

But about 80 million years ago — the day before yesterday in geologic time — this hump was a very big and active vol- cano. It is believed to be Texas’ only example of an exposed volcano that was formed underwater.

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