Geologic Provinces of the United States: Interior Plains gallery
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The Green River Valley
Mammoth Caves National Park
Photo by Phil Stoffer, USGS
The Green River has incised into the Pennyroal Plateau, a part of the ancient landscape surface that extended across the entire midwest region prior to the periods of glaciation starting in the Pliocene Epoch (about 5 million years ago). |
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Trail to Historic Cave Entrance
Mammoth Cave National Park
Photo by Phil Stoffer, USGS
The caprock of the Pennyroyal Plateau in the Mammoth Cave region are sandstone, shale, and conglomeratic beds. |
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First Creek Trail
Mammoth Cave National Park
Photo by Phil Stoffer, USGS
The Delaware River makes a sweeping bend as it heads throogh the
world-famous Delaware Water Gap. The bend of the river mimics the
underlying geology. |
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