Transcript Virginia Physical Geography

Virginia Physical Geography
The Physiographic Provinces of Virginia
Virginia has had a long, complex geologic history,
over 1.1 billion years
 Events that have led to the formation of a rich
diversity of rocks, and events that have folded, faulted
and rearranged those rocks in complex patterns.
 A physiographic province is a landform region, areas
divided according to similar terrain that has been
shaped by a common geologic history.
 Geographers recognize more than 20 physiographic
provinces in North America; five of these are in the
state of Virginia.

The Physiographic Provinces of
Virginia

Each province is characterized overall by
its elevation, relief, lithology, and geologic
structure. Because of the region’s history
of rock formation, deformation, and
erosion, specific types of landforms or
other geologic features may be associated
with a given province.
The Physiographic Provinces of
Virginia
Coastal Plain
The Coastal Plain is a flat area underlain by
young, unconsolidated sediments.
 Includes all of Virginia East of the Fall Line.
 The Fall Line is where Rivers cross from the
hard igneous and metamorphic rocks of the
Piedmont onto the soft roundest rocks in
Virginia.
 Deposits of sand, silt and clay including
marine fossils deposited by rivers.
 Layers of sediment were produced by
erosion of the Appalachian Mountains and
then deposited on the Coastal Plain.

Coastal Plain
The tilted beds of the Coastal Plain
extend offshore some 50 to 75 miles to
the edge of the North American
continent.
 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 Chesapeake Bay when sea
levels rose again and flooded the shelf

Coastal Plain
Piedmont
The Piedmont is an area of rolling hills underlain
by mostly ancient igneous and metamorphic
rocks.
 Igneous rocks are the roots of volcanoes formed
during an ancient episode of subduction that
occurred before the formation of the Appalachian
Mountains.
 The Piedmont is underlain by metamorphic
rocks of various origins that were folded during
the Paleozoic as the North American and African
plates converged. Later, in the Mesozoic, it was
affected by rifting as Pangaea broke apart and the
Atlantic Ocean formed.

Piedmont





Largest physiographic province.
Bounded on the east by the Fall Zone, and on
the west by the mountains of the Blue Ridge.
Rolling topography, deeply weathered bedrock
and rocks are strongly weathered.
Rocks are generally buried under a thick (220m) blanket of saprolite. ( a chemically
weathered rock)
Topography is more rugged closer to the Blue
Ridge.
Piedmont
Blue Ridge





The Blue Ridge is a high ridge of crystalline rock
separating the Piedmont from the Valley and Ridge
Province.
The billion-year old igneous and metamorphic rocks
of the Blue Ridge are the oldest in the state.
The Blue Ridge province experienced mountain
building during the late Neoproterozoic era (750700Ma).
In central and northern Virginia, the 570 million year
old basalts are over sedimentary rock.
Some metamorphism of these rocks occurred during
the formation of the Appalachian Mountains.
Blue Ridge
The Blue Ridge is composed of complexly
folded and faulted igneous (granitic) and
metamorphic rocks. These rocks date to the
PreCambrian and Paleozoic and represent parts
of the basement rock of the North American
continent.
 When Africa and North America converged
during the Paleozoic, these rocks were thrust
upward and many miles westward over younger
rock materials.

Blue Ridge
Valley and Ridge






Long parallel ridges and valleys of sedimentary rock which
were folded and faulted, and eroded differently.
540 million years old sandstones are overlain by carbonates
that make up a region of limestone and dolomite.
The folding and faulting of the sedimentary rocks occurred
during a collision between Africa and North America.
The collision, which occurred in the late Paleozoic, produced
the Appalachian Mountains.
Carbonates were deposited in a shallow tropical ocean
along the southeast edge of North America.
Carbonates in the Shenandoah Valley create the correct
environment for caves and sinkholes (Karst Topography)
Valley and Ridge
Appalachian Plateau




The Appalachian Plateau has rugged irregular
topography and is underlain by ancient, flatlying sedimentary rocks.
Large folds of rock found in the Valley and
Ridge become smaller folds and flat-lying
rocks in the Plateau.
Some parts of the Plateau are relatively flat,
and some are hilly and rugged.
The area is actually a series of plateaus
separated by faults. The upper layers of the
Plateau are rich in mineral resources like
coal, natural gas, and petroleum.
Appalachian Plateau
Watersheds of Virginia
Virginia is drained by three watersheds
 The Chesapeake Bay watershed which drain the
Northern and Eastern portion of the state This includes
The James, Rappahannock, Potomac, & York
 The North Carolina Sounds drain the south central
part of the state include the Chowan, and Roanoke
 The Mississippi River drains the western part of the
state includes the New and Big sandy Rivers

Watersheds of Virginia

Virginia Watersheds