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Big Bend National Park
Spires and cliffs of volcanic rocks on Pullman Mountain in the Chisos Mountains are part of the eroded remnants of the Sierra Quemada Caldera, a large intrusive and volcanic eruption complex that formed about 34 million years ago.
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U.S. Department of the Interior - U.S. Geological Survey - Geology Discipline
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Last modified: 4/1/2005

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