There are an estimated 200 volcanoes in Texas, expert says

Ancient Texas volcano responsible for the formation of several waterfalls near Austin

Nontronite at McKinney Falls State Park
Nontronite at McKinney Falls State Park (Texas Parks & Wildlife)

AUSTIN, Texas – Volcanoes in Texas? It’s true.

Texas history is rich with dinosaur footprints, fossils and gemstones but Texas was also once home to active volcanoes.

Linda McCall, an information geologist at the University of Texas at Austin, estimates that there are about 200 or so volcanoes in Texas and while none are active, she told KSAT it’s still possible they could become active again.

However, McCall noted that the last time a volcano erupted in Texas was about 30 million years ago in the Trans Pecos region.

“The Davis, Christmas, Bofecitos, and Chinati Mountains are all volcanic. In South and Central Texas, there are many remnants of marine volcanos that were present in the shallow seas about 80 million years ago. An example is Pilot Knob in Travis County and there are many others near Uvalde,” McCall said.

Pilot Knob is the closest volcano to San Antonio, just a few miles outside McKinney Falls State Park near Austin.

It may not look like a volcano to the common eye -- it appears to be just a rolling hill -- but Pilot Knob used to be active.

According to Tommy Cude, superintendent at McKinney Falls State Park, Pilot Knob was active around 80 million years ago.

Cude said visitors can see traces of the volcano’s past presence in the park because of something called nontronite.

“In the park, Pilot Knob deposited a layer of ash called nontronite. There is a layer of limestone on top of the ash and it erodes quicker than the limestone and created some of the waterfalls and rock shelters in the park,” Cude told KSAT.

“The volcanic rocks are very different in composition from sedimentary rocks, and the environment in these areas support special plants and animals,” McCall said. “The rocks and associated hydrothermal deposits are often rich in mineral deposits such as copper, silver, and lead. Mining operations are sometimes found in these areas.”

The Texas Parks and Wildlife website lists swimming as one of the many activities you can do at McKinney Falls State Park but cautions that Onion Creek can sometimes flood after heavy rains.

Pilot Knob itself is not accessible to the public because it is located on private property.

Charles “Chock” Woodruff previously told FOX 7 in Austin that Pilot Knob is the stump of a marine volcano and is actually part of series of long-dormant volcanoes that run northeast through Williamson County.

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