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USGS Geology in the Parks

Geologic Provinces of the United States: Appalachian Highlands gallery

Great Falls of the Potomac River

Great Falls of the Potomac River

Great Falls Park
Photo by Avery A. Drake, Jr, USGS

Erosion-resistant Late Proterozoic rock forms the Great Falls of the Potomac River in the Piedmont province of northern Virginia (left) and Maryland (right).

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Entrance to Delaware Water Gap

Entrance to Delaware Water Gap

Delaware Water Gap National Recreation Area
Photo by Jack B Epstein, USGS

The entrance to Delaware Water Gap National Recreation Area as viewed from atop Kittatinny Mountain, Pennsylvania on the right, New Jersey on the left.

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Delaware River

Delaware River

Delaware Water Gap National Recreation Area
Photo by Jack B Epstein, 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. Click here to learn more.

Ordovician and Silurian rocks

Ordovician and Silurian rocks

Delaware Water Gap National Recreation Area
Photo by Jack B Epstein, USGS

Exposure of Ordovician (Martinsburg) and Silurian (Shawangunk) rocks in Delaware Water Gap, New Jersey side. Click here to learn more.

Looking west from Loudoun Heights, Virginia

Looking west from Loudoun Heights, Virginia

Harpers Ferry National Historical Park
Photo by Scott Southworth, USGS

Looking west from Loudoun Heights, Virginia, to Harpers Ferry National Historical Park, West Virginia, at the confluence of the Shenandoah (left) and Potomac (right) Rivers. The low ridge just west of the terraced top of the town is underlain by fossil-bearing Cambrian metasandstone.

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Elk Ridge at Maryland Heights, Maryland

Elk Ridge at Maryland Heights, Maryland

Harpers Ferry National Historical Park
Photo by Scott Southworth, USGS

Looking north from Blue Ridge at Loudoun Heights, Virginia, to Elk Ridge, a large fold of Lower Cambrian rock is exposed along the water gap of the Potomac River. The C&O Canal National Historical Park is along the Potomac River in the lower part of the photograph.

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Clingmans Dome

Clingmans Dome

Great Smoky Mountains National Park
Photo by photo by Bob McDowell, USGS

At 6643 feet above sea level, Clingmans Dome is one of the highest peaks in the Appalachians. Click here to learn more.

Gregory Bald

Gregory Bald

Great Smoky Mountains National Park
Photo by Scott Southworth, USGS

Gregory Bald, at 4949 feet elevation above sea level, straddles the Tennessee and North Carolina border in Great Smoky Mountains National Park. The grassy "bald" in the immediate foreground is underlain by meter-deep, organic-rich soil developed on Precambrian graphitic slate and metasandstone. Click here to learn more.

Old Rag Mountain

Old Rag Mountain

Shenandoah National Park
Photo by Paul Hackley, USGS

View looking north to Old Rag Mountain, Shenandoah National Park, in the Blue Ridge province of Virginia. The craggy rock peak is exposed billion year old granitic gneiss called the Old Rag Granite. The low land in the foreground is a fluvial valley more characteristic of the Piedmont province to the east.

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Blue Ridge

Blue Ridge

Shenandoah National Park
Photo by Paul Hackley, USGS

View looking west to Blue Ridge from the crest of Old Rag Mountain. Outcrop and weathered boulders of billion-year-old Old Rag Granite is in the foreground. Blue Ridge forms the provincial boundary with the Great Valley of the Valley and Ridge province.

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Looking east from Blue Ridge

Looking east from Blue Ridge

Shenandoah National Park
Photo by Paul Hackley, USGS

Looking east from Blue Ridge. The craggy peaks are billion-year-old Old Rag Granite. Click here to learn more.

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