Background Information: Virginia’s Physiographic Provinces

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Background Information: Virginia’s Physiographic Provinces

Introduction

The Appalachian Mountains extend from Nova Scotia to Alabama, and include the state of Virginia.
Geographers and Geomorphologists recgnize more than 20 physiographic provinces in North
America. Virginia extends westward from the Atlantic Ocean to include parts of five provinces. The
topography and geology of the five provinces are unique unto themselves and are described below.

The Coastal Plain

The Coastal Plain is the youngest of Virginia’s physiographic provinces, it’s rocks having been
deposited after the Atlantic Ocean began to form early in the Mesozoic Era. It covers the eastern one-
fourth of the state and was once referred to as “Tidewater.” Today “Tidewater” designates the
Norfolk area.

The western boundary of the Coastal Plain is the Fall Line; this topographic break extends southward
from Washington, D.C. through Fredericksburg, Richmond, Petersburg, Emporia, and into North
Carolina. It was called the Fall Line because the zone of rapids or falls marks the transition from the
more resistant rocks to the west to the less resistant rocks and sediments of the Coastal Plain to the
east.

From the Piedmont where the elevation is about 200 feet above sea level, the Coastal Plain slopes
seaward continuing beneath the Atlantic Ocean to the edge of the continental shelf, about 600 feet
below sea level. The shoreline has been moving up (transgressing) for about 18,000 years at a rate of
2 to 3 feet every 100 years.

During the ice ages of the Pleistocene, sea level was lowered, exposing the shelf. Streams flowed
across the shelf and carved their valleys into it. One such large valley became the Chesapeake Bay
when sea levels rose again and flooded the shelf.

In the sediments of the Coastal Plain are reefs and fossilized shells, bones, and teeth. A fossil clam,
Chesapecten jeffersonius, was named the Virginia state fossil in 1992 because of its relative
abundance within the Pliocene-age Yorktown Formation and its name honors Thomas Jefferson’s
interest in fossils.

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The Piedmont

The largest of the provinces, the Piedmont, is directly west of the Coastal Plain and literally means
“foot of the hill” because the Blue Ridge, the highest mountains, is directly west. The Piedmont
covers the middle one-third of the state.

The Piedmont is an area of rolling landscape – gentle hills and valleys with a few isolated mountains
made of more resistant rocks. The Piedmont is characterized by deep weathered, very old erosion
surface. It widens from the northwest to the southwest, from 30 miles on the Maryland border to
about 160 miles at the North Carolina line. Elevation is from 1000-1300 feet to 200 feet at the Fall
Line.

Regionally, the Piedmont extends from Alabama to New Jersey. It is underlain by Precambrian and
Paleozoic metamorphic and igneous rocks and is more resistant to erosion than the Coastal Plain, so it
is a higher area. Within the Piedmont, there are found low-lying areas (basins) covered by Triassic
and Jurassic sediments intruded by igneous dikes and sills (also Mesozoic). These basins contain
unmetamorphosed sandstone and shale where dinosaur tracks have been preserved.

The Blue Ridge

The Blue Ridge is a long narrow area extending from southwest Virginia through the west-central
portion through the north-central part of the state. It has the highest peaks in the state.

The Blue Ridge is divided into two distinct parts: 1. Northeast of Roanoke – Very narrow (less than 2
miles across in some places like Afton Mountain on I-64), fairly rugged and reaches 4100 feet near
Luray. 2. Southwest of Roanoke – Here the Blue Ridge broadens into very high mature erosion
surfaces up to 50 miles wide. On the surface are peaks such as Mt. Rogers (5719 feet and the
highest), Whitetop Mountain, and Peaks of Otter.

Regionally, the Blue Ridge extends from Northwest Georgia to South-central Pennsylvania with the
widest part in eastern Tennessee to western North Carolina, and is called the Great Smokies.

The Blue Ridge contains mainly granite, gneiss, and metamorphosed igneous and sedimentary rocks.
They are very hard and resistant rocks and create the highest area in Virginia.

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The Valley and Ridge

The Valley and Ridge covers the western part of Virginia, from the Tennessee border to Maryland –
West Virginia. It consists of long, linear ridges (some greater than 4000 feet above sea level) with
well-defined long linear valleys in between. Trending northwest to southwest, the Valley and Ridge
is bounded by the Blue Ridge and the Plateau. Its long valley runs the length of the province on the
eastern border adjacent to the Blue Ridge and is known as the Shenandoah Valley in northern
Virginia, but it is generally called the Great Valley.

This province is composed of folded and faulted 550 to 300 million-year-old sedimentary rocks
(Paleozoic-age). Most ridges are held up by resistant sandstone, and most valleys are underlain by
less resistant shale, limestone, and dolostone. Underlain by mostly carbonate rocks, the valley of this
province is a region of Karst. Solution of the carbonate bedrock has created sinkholes on the surface
and many caves and large caverns beneath the surface.

Regionally, the Valley and Ridge extends from Alabama to Canada.

The Appalachian Plateau

In Virginia, the Appalachian Plateau province encompasses only the southwestern counties and
includes the Southwest Virginia coal field. This province contains a portion of the Cumberland
Plateau and is characterized by deep narrow valleys and steep, rugged mountainsides.

This province generally contains 320 to 280 million-year-old sandstone and shale formations with
coal beds. The rocks in this province have not been deformed as in the Valley and Ridge and still
occur today in horizontal beds.

Regionally, the Plateau extends from Alabama to New York.

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