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Volcanic Highlights and Features:
[This list is just a sample of
various West Virginia volcanic features or events and is by no means inclusive.]
- West Virginia
- West Virginia Regions
- West Virginia - Brief Geologic History
- West Virginia's Volcanic Rocks
- Volcanic Ash Deposits
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"The Mountain State"
With a nickname like "The Mountain State," there can be little doubt that
mountains have a special influence on the
hearts and minds of West Virginians. Mountains add immeasurably to
the majesty and beauty of the State.
West Virginia's Oldest Rocks:
In the extreme eastern part of the State are the oldest rocks,
and as one proceeds westward, the rocks are younger and
younger.
More specifically, the oldest rocks in the
east are very late Precambrian (the Catoctin
Formation) and then a nearly complete section
of the Paleozoic is exposed moving to the west.
There are no significant Mesozoic or Cenozoic
rocks in the State, but overlying most
formations is Quaternary alluvium.
Volcanoes in the Past:
While there are no volcanoes in West Virginia today,
they may have been present in the western part of
the State more that 550 million years ago.
Ash deposits from ancient volcanoes to the
east are found in the State.
Excerpts from:
West Virginia Geological Survey Website, 2001
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West Virginia's Physiographic Provinces:1
West Virginia is basically composed of two areas:
the western two-thirds of relatively flat-lying rocks
containing minable coal, and the eastern one-third
comprised of folded and faulted rocks with no
minable coal. The former area is the
Appalachian Plateau Province and the
latter is the Valley and Ridge Province
and they are separated by the Allegheny Front.
West Virginia's Appalachian Plateau:1
The Appalachian Plateau Province covers
the western two-thirds of the State where the
rock formations are relatively flat,
except for several distinct folds and faults on the eastern
side of the Province. The oldest rocks
are located in these eastern fold sequences and range
in age from late Ordovician up through
the Mississippian.
The majority of the Appalachian
Plateau is comprised of Pennsylvanian
and Permian strata and is where all the minable coal
is located. The rocks exposed in the
northern part of the Plateau are younger than those
exposed in the southern part.
West Virginia's Valley and Ridge:1
The Valley and Ridge Province in the east
is composed of folded and faulted rocks that
range in age from late Precambrian to early
Mississippian. The late Precambrian Catoctin
Formation is technically in the Blue Ridge
Province, but we only have limited outcrops
exposed on the Blue Ridge Mountains. From
the Blue Ridge Mountains westward for about
20 miles is the Great Valley. This relatively flat,
agriculturally rich region is composed of
complexly folded and faulted Cambrian and
Ordovician limestone and dolomite with one
prominent Ordovician shale (the Martinsburg Shale).
The Great Valley ends at North
Mountain and from here to the Allegheny Front,
a distance of about 50 miles, are a series of
northeast-trending mountains and valleys. The
rocks in this part of the Valley and Ridge
range in age from late Ordovician to
early Mississippian. The valleys are primarily
composed of less-resistant shale and siltstone,
while the mountain ridges are
mainly resistant sandstone and limestone.
West Virginia's Allegheny Front:1
The boundary between the two provinces, the
Allegheny Front, is a complex and rather
abrupt change in the topography, stratigraphy,
and structure. This boundary
extends southwestward across the
eastern part of the State, passes through Virginia,
and reenters the State in the southeast
in Monroe County.
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West Virginia - Brief Geologic History
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Precambrian - Earliest Rocks:2
Prior to one billion years ago, the geologic history of
West Virginia is obscure. Sometime between
about 1,100 and 800 million
years ago,
lava was deposited in the extreme eastern
part of the State forming our oldest exposed rock,
the Catoctin Greenstone.
Precambrian:1
Greenstone, present only in extreme eastern Jefferson County
Cambrian:1
Limestones and dolomites, some sandstone and shale
Ordovician:1
Limestone, dolomite, sandstone, others
Cambrian and Ordovician:2
Later, perhaps about 800 million years ago, a
narrow trough began to form in extreme eastern
West Virginia. An arm of the sea entered and
sediments accumulated. As time went on, this
shallow sea transgressed westward. By the end
of Cambrian time, about 300 million years later,
this shallow sea covered essentially all of
West Virginia. Marine deposition took place throughout
most of this and the succeeding Ordovician Period.
During this total interval of about 370 million
years, most of the rocks exposed in Jefferson
and eastern Berkeley counties and in scattered
areas southwestward along the Virginia boundary
were deposited. Rocks of the same age are
found in abundance in the deep wells throughout the State.
Taconic Orogeny:2
The Taconic Orogeny near the end of
Ordovician time formed a high mountainous area east of
West Virginia. These highlands formed
the main source of sediments for the succeeding Silurian
Period and part of the Devonian Period.
Both clastics and carbonates were deposited in a mixed
marine and nonmarine environment, with
clastics predominating in the eastern part of the State.
Evaporites were deposited in northern
West Virginia in Late Silurian time.
Devonian:1
Shale, sandstone, limestone, and chert.
Middle and Late Devonian - Acadian Orogeny:2
During Middle and Late Devonian time the
Acadian Orogeny, with the main uplift to the
northeast, resulted in a further source
for the predominantly clastic marine deposits
of these epochs. However, near the end of Devonian time,
the sea was rapidly
retreating westward and the continental red
beds of the Hampshire Formation were being
deposited over most of the State.
Mississippian:1
Limestone, shale, and sandstone
Middle Mississippian:2
The sea made one more important intrusion into
West Virginia during Middle Mississippian time,
approximately 330 million years
ago, resulting in the deposition of the
Greenbrier Formation, predominantly limestone,
the last marine deposit of significance in
the State.
Pennsylvanian:2
At the close of Mississippian time, about
310 million years ago, West Virginia was
essentially a land area, subject to erosion.
Early in the succeeding Pennsylvanian Period,
the area dropped to near sea level and for more
than 50 million years continued to
sink at about the same rate that deposition
was taking place. Only occasionally and for
very short periods of time did the area fall
below sea level. Swamp conditions prevailed,
resulting in the deposition of thousands of
feet of nonmarine sandstone and shale
and the many important coal seams that we know today.
Permian - Appalachian Orogeny:2
Sometime during the Permian Period,
roughly 270 to 225 million years ago,
the Appalachian Orogeny began. West Virginia was
uplifted, important deposition of
sediments ceased, and erosion began taking place.
Much folding and thrust faulting occurred,
especially in the eastern part of the State.
This orogeny played a major part in the formation of
the Appalachian Mountains as we
know them today. Never again has the
sea invaded West Virginia.
Mesozoic:2
So far as is known, no sedimentary rocks
were deposited in West Virginia during the
Mesozoic Era, which extended from 225 to
66 million years ago.
During the early part
of the era,
considerable
igneous activity
took place in neighboring states to the east,
and a few dikes of
diabase and other basic rock
extended into Pendleton and surrounding counties.
Cenozoic - Glaciers:2
Late in the Cenozoic Era, in fact
extending to less than 100,000 years ago,
glaciers covered the northern part of the North
American continent, extending almost to
the Northern Panhandle of West Virginia,
but not into the State. Prior to the advance of
these ice sheets, drainage of the Monongahela River
was northward to the St. Lawrence River system. The ice sheet caused
damming and a lake extended as far south as Weston.
Important lake deposits, predominantly clay,
were thus laid down in the
Monongahela River basin. Drainage was diverted
westward into the Ohio River system.
Divergence of the New River system
that formerly drained northwestward caused the
deposition of similar deposits in the
old Teays River channel between
Charleston and Huntington. Except for recent
alluvial deposits, there are no other
known Cenozoic rocks.
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West Virginia's Volcanic Rocks
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Catoctin Greenstone:1
Prior to one billion years ago, the geologic history
of West Virginia is obscure. Sometime between about 1,100 and
800 million years ago, lava
was deposited in the extreme eastern part
of the State forming the oldest exposed rock,
the Catoctin Greenstone.
The oldest bedrock (rock in place)
exposed at the surface is found
in the southeastern tip of Jefferson County.
These rocks, of the
Catoctin Formation, are approximately 570 million years old
(Precambrian age) and consist of metamorphosed basalt lava flows.
It is possible that some rock fragments even older than this
(such as granites)
were transported in glacial till and occur in Ohio River
outwash, but these are not native to West Virginia.
Dikes, Sills, Plugs:1
There are no granite
bodies exposed in West Virginia.
Workers from the Survey have identified a number of "shallow," intrusive
igneous dikes, sills, and plugs with compositions ranging from
basalt to andesite that cut across sedimentary rocks
of Ordovician through Devonian age. These rocks are
exposed at the surface in
Pendleton County and are reported
in subsurface well drilling records
from other counties such as Pocahontas.
These dikes, sills, and plugs are younger than the rocks they cut.
Research by the U.S. Geological Survey and others indicate that the
majority of these igneous intrusive rocks are Middle Eocene
in age and thus, are considerably younger than the last stages of
mountain-building associated with the Appalachian Orogeny or the
Mesozoic rifting that opened the present-day Atlantic Ocean.
During the Middle Eocene, the eastern coast of North America
is thought to have been a "passive" continental margin, much like today.
The presence of igneous activity in such a
setting is unexpected and, as yet, unexplained.
Diabase Dikes:2
So far as is known, no sedimentary rocks
were deposited in West Virginia during the
Mesozoic Era, which extended from 225 to
66 million years ago.
During the early part
of the era,
considerable igneous activity
took place in neighboring states to the east,
and a few dikes of
diabase and other basic rock
extended into Pendleton and surrounding counties.
Volcanic Ash Deposits:1
There is evidence of multiple ash falls from ancient
volcanoes preserved in rocks of Cambrian,
Ordovician, and Devonian age in outcrops
in eastern West Virginia and in the subsurface in
the western part of the State, and in a
flint clay in the Hernshaw coal bed of
Middle Pennsylvanian age (Kanawha Formation) in
southern West Virginia. The sources of
these ash falls are speculated to have been
ancient volcanoes -- long ago eroded -- to the
southeast of what is now West Virginia.
All of these events occurred more than
300 million years ago.
Excerpts from:
1) West Virginia Geological Survey Website, 2001
2) West Virginia Geological Survey Website, 2002,
West Virginia Historical Geology,
Originally adapted from an
educational booklet by Dudley Cardwell, 1975
3) USGS/NPS Geology in the Parks Website, 2001
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