Geology of Pennsylvania
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The Geology of Pennsylvania consists of six distinct physiographic provinces, three of which are subdivided into different sections. Each province has its own economic advantages and geologic hazards and play an important role in shaping every day life in the state. They are: (listed from the southeast corner to the northwest corner) the Atlantic Coastal Plain Province, the Piedmont Province, the New England Province, the Ridge and Valley Province, the Appalachian Plateau Province, and the Central Lowlands Province.[1]
The most famous rock from Pennsylvania is Anthracite coal. Before it was mined there was an estimated 22.8 billion tons of anthracite in Pennsylvania. As of 2001, 12 billion tons still remain in the ground. (Most of which is not economically feasible to mine)[2] American geologists recongized the importance of Pennsylvania's coal region and named the Upper Carboniferous Period the Pennsylvanian Period because of the abundance of coal in the state.
Pennsylvania is also home to the famous Drake Oil Well in Titusville.
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[edit] Atlantic Costal Plain
One of the smallest provinces in the state and is confined to Philadelphia, Delaware, and Bucks counties along the Delaware River. Local relief is less than 200 feet and much of the bedrock is burried under recent alluvial deposits. The costal plain in Pennsylvania was once home to thousands of acres of fresh water tidal marsh. This was important in the early devlopment of Philadelphia and Chester. Many of the small tributaries to the Delaware have cut small but impressive gorges into the bedrock including the Ridley Creek, the Chester Creek, and the Wissahickon Creek. Flash floods are becoming a local problem in the province.
[edit] Piedmont
The piedmont in Pennsylvania is divided into three distinct sections: the Piedmont Uplands, the Piedmont Lowlands, and the Gettysburg-Newark Lowlands. Much of the Piedmont is becoming urbanized and developed. Some of the best farmland in the state is in this region, specifically Lancaster and Chester counties.
[edit] Piedmont Uplands
This section is characterized by the metamorphic rocks that provide much of the bedrock for this area. Gneiss, Schist, Quartzite, and Serpentinite are some of the rocks that make up this region. These rocks have a complex history that is still being researched to this day. The Baltimore Gneiss is a Pre-Cambrian basement rock that has been dated as much as 1 billion years old. Most of the hills are broad and rolling with shallow vallies.
[edit] Piedmont Lowlands
The lowlands are underlain primairly by more easily eroded rocks such as limestone, dolostone, and phyllite. Relief is low and generally never rises above 700 feet. Karst terrain is problematic in this section.
[edit] Gettysburg-Newark Lowlands
This section is a bit misleading since there are hills as high as 1,200 feet in this section. It is separated from the rest of the Piedmont sections due to the distinctive rock types found here. Also called the Triassic Basin, most of the bedock are red sandstone, siltstone, and shale. A few formations are brown and black. The sediment accumulated during the rifting of Pangea in the Triassic age. Also, a basaltic igneous rock called diabase formed dykes and sills later in the Jurassic as the Atlantic Ocean began to form.[3] Much of the rocks from this area ave been eroded away, but the more erosion resistant diabase has left hills and small elevated regions throughout the section. The erosion patterns of these rocks played a pivotal role in the Battle of Gettysburg.[4]
[edit] New England
Only a small and fragmented province in Pennsylvania called the Reading Prong. This is the southern end of the Hudson Highlands of New York and New Jersey (known as the Ramapo Mountains in New Jersey) and the Taconic Mountains of New York. The granitic rocks and quartzite of this area are highly metamorphosed and are Pre-Cambrian to Cambrian in age. Hills and ridges are locally steep and rounded at the top and form the hills around Reading, and to the south of the Allentown-Bethlehem-Easton metropolitan area. (See also South Mountain)
[edit] Ridge and Valley
A region in Pennsylvania made famous by NASA's LANDSAT images. This province is the second largest in the state and is home to the famous anthracite fields. The rocks here are severly folded and contain numerous anticlines and synclines that plunge and fold back over each other. There are numerous thrust faults that help create a chaotic mess. Most of the deformation is result of continent to continent collision during the Alleghenian orogeny. There are seven distinct regions of the provence and are listed below. Much of the drainage patterns in the province is trellis.
[edit] South Mountain
South Mountain is the northern tip of the Blue Ridge Mountains. This region is charcterized by broad flat ridges with deep narrow valleys. The rocks here are highly metamorphosed igneous and sedimentry rocks with some occasional dolomite. These rocks are Pre-cambrian in age.
[edit] Great Valley
The Great Appalachian Valley is a long broad valley that extends from Canada to Alabama. In Pennsylvania, the valley is known by three names: (listed from north to south) the Lehigh Valley, the Lebanon Valley, and the Cumberland Valley. Rocks that characterize this region include: limestone, dolostone, slate, shale, sandstone, siltstone, and some scattered basalt. Almost all of the rocks in the Great Valley in Pennsylvania are Ordovician in age and were deposited during a quiet period before the Taconic orogeny. The limestones and dolostones of this area are extensively quarried in Pennsylvania. These carbonate rocks are used for variety of purposes inculding, crushed stone, cement manufacturing, fertilizers, and coal-mine dust (reduces acid mine drainage)[5] Karst features are problematic in the Great Valley.
[edit] Blue Mountain
This region is not to be confused with the Blue Ridge Mountains but instead, represents the sharp escarpment separating the Appalachian Mountains from the Great Valley. Many of Pennsylvania's water gaps cut through Blue Mountain including Delaware Water Gap, Lehigh Gap, Schuylkill Gap, and Susquehanna Gap. Also along the ridge, many "wind gaps" also exist. (see separate article) The rocks of the Blue Mountain section include mostly Silurian aged sandstone, conglomerate, siltstone, shale, and some limestone. Blue mountain is also known by the names: Kittatinny Mountain (especially in New Jersey) and Hawk Mountain. One of the most promient rock types of this section is the Shawangunk Formation which is named after the Shawangunk Ridge of New York.
[edit] Anthracite Upland
Arguably the most complex and most studied section in the state. This area is home to one of Pennsylvania's most profitable coal fields ever, containing high-grade Anthracite coal. Mountains are steep-sided and valleys are canoe-shaped, largely due to its complex folded structure. Other than coal, cyclical sequences of shale, sandstone, and conglomerate also make up this region. The rocks are from the Carboniferous period, divided into the Mississippian and Pennsylvanian periods with almost all of the coal being mined from Pennsylvanian-aged formations. Along with the Mazon Creek fossil field in Illinois, a tremendous amount of plant fossils have been studied from this area.[6] Landsides and acid mine drainage are two principle hazards of the area. In the past, underground mine fires have also been a threat. The Centralia Mine Fire is located within this section.
[edit] Anthracite Valley
Detached from the rest of Pennsylvania's anthracite fields, this canoe shaped valley is also known as the Lackawanna Valley and his home to Scranton and Wilkes-Barre. The whole strcture of the section is a double plunging syncline with sharp mountain ridges on either side of the valley. The ridges meet just north of Carbondale. The East Branch of the Susquehanna River along with the Lackawanna River flow through this valley. Large-scale coal minning along with its accompanying industry, railroads, have long been abandonned.
Unlike the southern and middle anthracite fields, the anthracite valley has been recently glaciated repeatedly. This has left many talus slopes at the base of Moosic Mountain, and the soils often contain large boulders making excavation difficult.
[edit] Susquahanna Lowland
This region has also seen its landscape altered by glaciation and the fluvial processes of the Susquehanna River. Most of the ridges in this region are parallel to the streams that drain the area. The Susquehanna also cuts through many of the mountain ridges leading some to believe that the Susquehanna is an ancient river system that existed even before the recent continental glaciation. (Some speculate as far back as the Cretaceous Period)[7] None of the mountains in this section rise above 1,700 feet and the river valley is as low as 250 feet.
[edit] Appalachian Mountain
The standard long, narrow, and steep sided ridges with narrow valleys that define the state in LANDSAT photos. Many of the valleys have karst features due to carbonate rocks that reside in them. Road building generally follows the vallleys and rarely cut across the ridges. The Pennsylvania Turnpike cut tunnels into the ridges rather than scale the mountain tops. Mount Nittany, Tuscarora Mountain and Sideling Hill are three prominent mountains in this section
[edit] Appalachian Plateau
By far the large provience in the state, most of the rocks in this region are not folded and faulted and sit relatively flat. In western Pennsylvania, large bituminous coal fields exist in rocks with a simialr age as the rocks in the anthracite region. Many of the folds in the province are high amplitude and strech for miles. In glaciated sections, steep canyons developed and much of the terrain have many glacial features. The drainage pattern in this area is dendritic.
[edit] Glaciated Pocono Plateau
The Pocono Mountain section of Pennsylvania is the same (geologically speaking) as the Catskill Mountains of New York. The red-green-gray sedimentary rocks of the Catskill Formation are the predomiant bedrock type in the Poconos. The elevation of the plateau is between 1,200 and 2,300 feet with only a few steep hills. (Camelback Mountain for example) Much of the rock sits in gently dipping horizontal beds, unlike the neighbooring Appalachian Mountain section.
[edit] Glaciated Low Plateau
Considered a part of the Pocono Plateau, this area lies to the north of the poconos and contains many of the same types of rock. The local relief is less than that of the Pocono region and bounded to the southeast by the Delaware River. The Bush Kill cuts a gorge through this section and has many waterfalls especially around the area of Resica Falls Scout Reservation. Dingmans Falls and Bushkill Falls are waterfalls within the Delaware Water Gap National Recreation Area. Also a part of the Endless Mountain region of Pennsylvania.
[edit] Glaciated High Plateau
Also an extension of the Catskill Mountains of New York, this section generally has higher elevations that the low plateau section as well as deeper valleys. Younger strata also outcrops in this area with a few minor coal beds. The uplands are rounded or flat along mostly broad hills. An excellent example of the escarpment that divides this section are Ricketts and Ganoga Glen located within Ricketts Glen State Park.
[edit] Deep Valleys
This section is home to the Grand Canyon of Pennsylvania and some of the most remote areas of the state. As the name implies, the streams of this area have cut deep valleys with steep sided slopes of the surrounding ridges. Some of the gorges are at least 1,000 feet deep. Much of the area was forested at the end of the 19th century and much of the area is owned by the Pennsylvania Buraeu of Forestry.
[edit] Allegheny Front
This section includes the abrupt escarpment that divides the Ridge and Valley Provience from the Allegheny Plateau. The region is a large broad ridge with a steep ascent from east to west and rolling hills away from the ridge. Streams that do cut into the ridge are often shallow and steep.
[edit] Allegheny Mountain
This section includes Pennsylvania's highest point, Mount Davis which stands at 3,213 feet above sea level. Many of the mountains are long and broad with realtively shallow and broad valleys. Unlike the Appalachian Mountain section, the streams of this area have not cut deep and well defined valleys into the earth. Much of the drainage pattern is dendrtic with a little trellis where erosion resistant rocks have created higher and more well defined ridges. Elevations increase to the south and Mt. Davis resides only 50 miles from the Maryland border. A few of the ridge tops contain some Low-volatile bitminous coal fields including the Broad Top field.[2] This region is also home to two national stories: the Quecreek Mine Rescue and the crash of United Airlines Flight 93.
[edit] Waynesburg Hills
Located in the southwest corner of the state, the Waynesburg hills are another major coal producing area for state. Much of the 64.4 billion tons of bituminous coal that is remaining in the state resides under these hills in near horiztonal beds. The hills are narrow and steep sided with some deeper valleys.[2]
[edit] Pittsburgh Low Plateau
Another section that is a significant coal producer. It is similar to the Waynesbrug hills section expect for higher local relief and deeper valleys. Landslides and mine subsidence are common hazards.
[edit] High Plateau
This section consists of high, broad, and flat uplands cut by sharp and shallow river valleys. Much of this area was not covered by the Late Wisconsinan glacier but there is evidence of pre-Wisconsinan glaciers in the area.
[edit] Northwestern Glaciated Plateau
This section has been influenced by glaciers and many of the valleys cutinto the bedrock trend northwestward- in the direction of the retreating glaciers. There are many signs of glaciers including kames, kettles, and moraines. Some of the drainage patterns have shifted and only a few of streams flow into Lake Erie.
[edit] Central Lowlands
Along with the Coastal Plain Province, the smallest province in the state, the central lowlands are a part of the Great Lakes area and exists along a glacial escarpement adjecent to Lake Erie. The only economic factor in this province is the port of Erie.
[edit] Geologic Features
The following is a lsit of notable Pennsylvania geologic features noted for their bueaty and/or uniqueness.
[edit] Glacial
- Archbald Pothole
- Grand Canyon of Pennsylvania
- Hickory Run State Park
- McConnells Mill State Park
- Moraine State Park
- Presque Isle
- Promised Land State Park
- Ricketts Glen State Park
[edit] Structural
- Chickies Rock
- Delaware Water Gap
- Ringing Rocks
- The Pinnacle
- Whale Back
[edit] Notable Rock Formations
- Allegheny Formation
- Bloomsburg Formation
- Catskill Formation
- Conemaugh Group
- Dunkard Group
- Llewellyn Formation
- Martinsburg Formation
- Mauch Chunk Formation
- Passaic Formation (former Brunswick Formation)
- Pottsville Formation
- Shawangunk Formation
- Tuscarora Formation
- Wissahickon Formation
[edit] Trivia
- Celestine was proposed as the state mineral in 2002. The proposal however, was not approved.[8][9]
- Quaker State (now owned by Royal Dutch Shell) and Pennzoil are brand name motor oils that originate from the oil fields of Pennsylvania.
[edit] Outside Links
- The Pennsylvania Geologic Survey
- Physiographic Provinces of Pennsylvania
- The Geologic Story of Pennsylvania
[edit] References
- ^ Sevon, W.D. (2000). Physiographic Provinces of Pennsylvania, Map 13. Pennsylvania Geologic Survey. Harrisburg, PA.
- ^ a b c Edmunds, W.E., (2002), Coal in Pennsylvania (2nd ed.): Pennsylvania Geological Survey, Educational Series 7, p. 17.
- ^ Faill, R.T. (2004). The Birdsboro Basin. Pennsylvania Geology, Pennsylvania Geologic Survey, Harrisburg, PA. V 34 n 4.
- ^ Smith, R.C. and Keen, R.C., (2004). Regional Rifts and the Battle of Gettysburg. Pennsylvania Geology, Pennsylvania Geological Survey, Harrisburg, PA. V 34 n 3.
- ^ Barnes, J.H. and Smith, R.C., II, (2001). The nonfuel mineral resources of Pennsylvania: Pennsylvania Geological Survey, Educational Series 12.
- ^ Oleksyshyn, J., (1982). Fossil plants from the anthracite coal fields of eastern Pennsylvania: Pennsylvania Geological Survey, Harrisburg, PA.
- ^ citation needed
- ^ http://www.dcnr.state.pa.us/topogeo/collecting/rocks.aspx
- ^ Edwin, C., (2003). Celestine, the Proposed State Mineral. Pennsylvania Geology, Pennsylvania Geological Survey, Harrisburg, PA. V 33 n 1.
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