Download Geology of Virginia Notes

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Geology of Virginia Notes
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The Coastal Plain extends from the Fall Zone eastward to the Atlantic Ocean.
Through the Fall Zone, the larger streams cascade off the resistant igneous and
metamorphic rocks of the Piedmont to sea level. (A fall zone is the break between
an upland region of relatively hard rock and a coastal plain of softer sedimentary
rock).
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The Chesapeake Bay was created about 5000 to 6000 years ago when the lower
course of the Susquehanna River was flooded as meltwater from the continental
glaciers raised sea level.
The Virginia Coastal Plain is underlain by sediments. These sediments were
stripped from the Appalachian Mountains, carried eastward by rivers and
deposited in deltas in the newly formed Atlantic Ocean basin.
The Peidmont has gently rolling topography and deeply weathered bedrock
because of the humid climate.
A variety of igneous and metamorphic rocks make up the bedrock of the
Piedmont province. Most of these rocks range in age from Proterozoic to
Paleozoic and form the internal core of the ancient Appalachian mountain belt.
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Sedimentary rocks, dikes, and basalt flows are present in a number of grabens
that formed during the early stages of rifting associated with the opening of the
Atlantic Ocean.
Some igneous rocks are thought to be the remains of an ancient volcanic arc that
collided with and accreted (attached) onto the eastern edge of North America
during a period of Appalachian mountain building.
The Blue Ridge province has been thrust to the northwest over Paleozoic rocks
of the Valley & Ridge Province .
The Blue Ridge experienced the intrusion of plutons.
In the western Blue Ridge, shallow marine sediments were deposited in the early
Cambrian and eventually gave way to carbonates.
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The Valley & Ridge province consists of parallel ridges and valleys that are
underlain by folded sedimentary rock. The characteristic topography of this
region is the result of differential weathering of linear belts of rocks that have
been repeated by folding and faulting.
For at least 70 million years carbonates were deposited in a shallow tropical
ocean along the southeast edge of North America.
Well-developed karst topography is characteristic of the Shenandoah Valley and
many caverns are located in the subsurface.
Much of the Appalachian Plateau is strongly eroded by streams and the
topography is rugged.
The upper strata of the Plateau are rich in mineral resources such as coal,
Natural gas and petroleum.