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162-550: 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 plays an important role in shaping everyday life in the state. From the southeast corner to the northwest corner of the state, they include: the Atlantic Plain Province , the Piedmont Province ,
324-1045: A Farmer in Pennsylvania, To the Inhabitants of the British Colonies , which were published in the Pennsylvania Chronicle between December 2, 1767, and February 15, 1768. When the Founding Fathers convened in Philadelphia in 1774, 12 colonies sent representatives to the First Continental Congress . The Second Continental Congress , which began in May 1775, authored and signed the Declaration of Independence in Philadelphia, but when Philadelphia fell to
486-766: A century, the Pennsylvania General Assembly met at various places in the Philadelphia area before it began meeting regularly in Independence Hall in Philadelphia for 63 years. However, events such as the Paxton Boys massacres of 1763 had made the legislature aware of the need for a central capital. In 1799, the General Assembly moved to the Lancaster Courthouse. The Pennsylvania General Assembly met in
648-408: A distinctive composition or mode or origin. Special names still in wide use include amphibolite, greenschist , phyllite, marble, serpentinite , eclogite, migmatite , skarn , granulite , mylonite, and slate. The basic classification can be supplemented by terms describing mineral content or texture. For example, a metabasalt showing weak schistosity might be described as a gneissic metabasalt, and
810-455: A distinctive layering called foliation (derived from the Latin word folia , meaning "leaves"). Foliation develops when a rock is being shortened along one axis during recrystallization. This causes crystals of platy minerals, such as mica and chlorite , to become rotated such that their short axes are parallel to the direction of shortening. This results in a banded, or foliated, rock, with
972-520: A grant that incorporated all lands included in the original Virginia Company of Plymouth Grant and other lands. This grant was in conflict with the Dutch claim for New Netherland , which included parts of today's Pennsylvania. On June 24, 1664, the Duke of York sold the portion of his large grant that included present-day New Jersey to John Berkeley and George Carteret for a proprietary colony. The land
1134-451: A heavy snowstorm, presumably because of a faulty flue . The General Assembly met at a nearby Methodist Church until a new capitol could be built. Following an architectural selection contest, Chicago architect Henry Ives Cobb was asked to design and build a replacement building. However, the legislature had little money to allocate to the project. When they dubbed the roughly finished, somewhat industrial Cobb Capitol building complete,
1296-457: A leader in technology and healthcare. Similarly, Philadelphia has a concentration of university expertise. Healthcare, retail, transportation, and tourism are some of the state's growing industries of the postindustrial era. As in the rest of the nation, most residential population growth has occurred in suburban rather than central city areas, although both major cities have had significant revitalization in their downtown areas. Philadelphia anchors
1458-701: A local problem in the province. 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. This section is characterized by the metamorphic rocks that provide much of
1620-469: A marble will not be identical with the amphibolite facies of a pelite. However, the facies are defined such that metamorphic rock with as broad a range of compositions as is practical can be assigned to a particular facies. The present definition of metamorphic facies is largely based on the work of the Finnish geologist, Pentti Eskola , with refinements based on subsequent experimental work. Eskola drew upon
1782-533: A metamorphic rock to be classified in this manner, the protolith should be identifiable from the characteristics of the metamorphic rock itself, and not inferred from other information. Under the British Geological Survey's classification system, if all that can be determined about the protolith is its general type, such as sedimentary or volcanic, the classification is based on the mineral mode (the volume percentages of different minerals in
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#17327880352741944-709: A part of the Endless Mountains region of Pennsylvania. Also an extension of the Catskill Mountains of New York, this section generally has higher elevations than 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 . This section
2106-413: A pelite containing abundant staurolite might be described as a staurolite pelite. [REDACTED] A metamorphic facies is a set of distinctive assemblages of minerals that are found in metamorphic rock that formed under a specific combination of pressure and temperature. The particular assemblage is somewhat dependent on the composition of that protolith, so that (for example) the amphibolite facies of
2268-516: A quiet period before the Taconic orogeny . The limestones and dolomites of this area are extensively quarried in Pennsylvania. These carbonate rocks are used for variety of purposes including, crushed stone, cement manufacturing, fertilizers, and coal-mine dust (reduces acid mine drainage ) Karst features are problematic in the Great Valley. The Blue Mountain or Blue Ridge region, like
2430-504: A quiet stretch of shallow sea deposition. Some of the rocks deposited during this time are also found in the Great Valley section but have been separated by the Gettysburg-Newark Lowland section. Relief is low and generally never rises above 700 feet (210 m). Karst terrain is problematic in this section. This section is a bit misleading since there are hills as high as 1,200 feet (366 m) in this section. It
2592-519: A relatively mild grade of metamorphism, at temperatures of 350–500 °C (662–932 °F) and pressures of 200–500 MPa (2,000–5,000 bar). They can be divided into a lower group of metabasalts, including rare meta komatiites ; a middle group of meta-intermediate-rock and meta-felsic-rock; and an upper group of metasedimentary rock. The greenstone belts are surrounded by high-grade gneiss terrains showing highly deformed low-pressure, high-temperature (over 500 °C (932 °F)) metamorphism to
2754-502: A similar age as the rocks in the anthracite region. Many of the folds in the province are high amplitude and stretch 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 . The Pocono Mountains section of Pennsylvania is the same geologically as the Catskill Mountains of New York. The red-green-gray sedimentary rocks of
2916-538: A tremendous amount of plant fossils has been studied from this area. Landslides and acid mine drainage are two principal hazards of the area. In the past, underground mine fires have also been a threat. The Centralia Mine Fire is located within this section of the Ridge and Valley province. Detached from the rest of Pennsylvania's anthracite fields, this canoe-shaped valley is also known as the Wyoming Valley and
3078-410: A variety of metamorphic facies. Where subduction is taking place, the basalt of the subducting slab is metamorphosed to high-pressure metamorphic facies. It initially undergoes low-grade metamorphism to metabasalt of the zeolite and prehnite-pumpellyite facies , but as the basalt subducts to greater depths, it is metamorphosed to the blueschist facies and then the eclogite facies . Metamorphism to
3240-417: Is a great variety of metamorphic rock types. In general, if the protolith of a metamorphic rock can be determined, the rock is described by adding the prefix meta- to the protolith rock name. For example, if the protolith is known to be basalt , the rock will be described as a metabasalt. Likewise, a metamorphic rock whose protolith is known to be a conglomerate will be described as a metaconglomerate . For
3402-490: Is a list of Pennsylvania geologic features noted for their beauty and/or uniqueness. Pennsylvania has been updating its base geologic map last printed in 1980. New research has shifted the names of several formations and promoted or demoted many different sequences on the stratigraphic chart. Pennsylvania Pennsylvania ( / ˌ p ɛ n s ɪ l ˈ v eɪ n i ə / PEN -sil- VAY -nee-ə , lit. ' Penn's forest country ' ), officially
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#17327880352743564-648: 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, dolomite, 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
3726-766: Is also known by the names Kittatinny Mountain (especially in New Jersey) and Hawk Mountain . One of the most prominent rock types of this section is the Shawangunk Formation , which is named after the Shawangunk Ridge of New York state. The sediments that comprise Blue Mountain were deposited as a result of the highlands that formed after the Taconic orogeny. The first wave of sediments were coarse, gray, and poorly sorted. (The Shawngunk Formation) This combination of depositional features means that
3888-426: Is called a paired metamorphic belt . The main islands of Japan show three distinct paired metamorphic belts, corresponding to different episodes of subduction. Metamorphic rock is also exposed in metamorphic core complexes , which form in region of crustal extension. They are characterized by low-angle faulting that exposes domes of middle or lower crust metamorphic rock. These were first recognized and studied in
4050-515: Is dominated by metamorphic rock that has reached the amphibolite facies. Within the upper crust, which is the only part of the Earth's crust geologists can directly sample, metamorphic rock forms only from processes that can occur at shallow depth. These are contact (thermal) metamorphism , dynamic (cataclastic) metamorphism , hydrothermal metamorphism , and impact metamorphism . These processes are relatively local in occurrence and usually reach only
4212-476: Is formed as tectonic plates move apart. Hydrothermal metamorphism is extensive here. This is characterized by metasomatism by hot fluids circulating through the rock. This produces metamorphic rock of the greenschist facies. The metamorphic rock, serpentinite , is particularly characteristic of these settings, and represents chemical transformation of olivine and pyroxene in ultramafic rock to serpentine group minerals. Contact metamorphism takes place when magma
4374-577: Is home to Pennsylvania's largest natural lake, Conneaut Lake as well as one of the longest eskers in the state, West Liberty Esker . Some of the drainage patterns have shifted and only a few of the streams flow into Lake Erie. Along with the Coastal Plain Province, the smallest province in the state, the central lowlands are a part of the Great Lakes area and exist along a glacial escapement adjacent to Lake Erie . The following
4536-579: 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 on the surrounding ridges. Some of the gorges are at least 1,000 feet (305 m) deep. Much of the area was forested at the end of the 19th century, and much of the area is owned by the Pennsylvania Bureau of Forestry . The Allegheny Front section includes
4698-639: Is home to the cities of Scranton and Wilkes-Barre . The largest city in the Wyoming Valley is Scranton, with a population of 77,291. The whole structure 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 North Branch of the Susquehanna River and the Lackawanna River flow through this valley. Large-scale coal mining and its accompanying industry and railroads have long been abandoned. Unlike
4860-849: Is in Duncannon in Perry County . According to the U.S. Department of Housing and Urban Development 's 2022 Annual Homeless Assessment Report , there were an estimated 12,691 homeless people in Pennsylvania. Among Pennsylvania residents, as of 2020, nearly three out of four, 74.5%, are native to the state and were born in Pennsylvania, 18.4% were born in a different U.S. state, 1.5% were born in Puerto Rico , U.S. Island areas, or born abroad to American parent(s), and 5.6% were foreign born. Foreign-born Pennsylvanians are largely from Asia (36.0%), Europe (35.9%), and Latin America (30.6%) with
5022-403: Is injected into the surrounding solid rock ( country rock ). The changes that occur are greatest wherever the magma comes into contact with the rock because the temperatures are highest at this boundary and decrease with distance from it. Around the igneous rock that forms from the cooling magma is a metamorphosed zone called a contact aureole . Aureoles may show all degrees of metamorphism from
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5184-405: Is known as burial metamorphism . This tends to produce low-grade metamorphic rock. Much more common is metamorphic rock formed during the collision process itself. The collision of plates causes high temperatures, pressures and deformation in the rocks along these belts. Metamorphic rock formed in these settings tends to shown well-developed schistosity. Metamorphic rock of orogenic belts shows
5346-521: Is remaining in the state resides under these hills in near horizontal beds. The hills are narrow and steep-sided, with some deeper valleys. Another section that is a significant coal producer. It is similar to the Waynesburg hills section except for higher local relief and deeper valleys. Landslides and mine subsidence are common hazards. This section consists of high, broad, and flat uplands cut by sharp and shallow river valleys. Much of this area
5508-520: 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 bedrock 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
5670-506: Is sufficiently hard and dense that it is difficult to quarry. However, some quartzite is used as dimension stone , often as slabs for flooring, walls, or stairsteps. About 6% of crushed stone, used mostly for road aggregate, is quartzite. Marble is also prized for building construction and as a medium for sculpture. Schistose bedrock can pose a challenge for civil engineering because of its pronounced planes of weakness. A hazard may exist even in undisturbed terrain. On August 17, 1959,
5832-610: Is the 33rd-largest by area and has the ninth-highest population density among all states. The largest metropolitan statistical area is the southeastern Delaware Valley , which includes and surrounds Philadelphia, the state's largest and nation's sixth-most populous city. The second-largest metropolitan area, Greater Pittsburgh , is centered in and around Pittsburgh , the state's second-largest city. The state's subsequent five most populous cities are Allentown , Reading , Erie , Scranton , and Bethlehem . Pennsylvania's history of human habitation extends thousands of years before
5994-464: Is the fifth-most populated state in the U.S. after California , Texas , Florida , and New York . In 2019, net migration to other states resulted in a decrease of 27,718, and immigration from other countries resulted in an increase of 127,007. Net migration to Pennsylvania was 98,289. Migration of native Pennsylvanians resulted in a decrease of 100,000 people. 7.2% of the population was foreign-born as of 2021. Pennsylvania's center of population
6156-475: Is the second-largest in the state and home to the famous anthracite fields. The rocks here are severely 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
6318-707: 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 Lehigh Valley on South Mountain . This region in Pennsylvania, made famous by NASA 's LANDSAT images,
6480-553: Is transformed physically or chemically at elevated temperature, without actually melting to any great degree. The importance of heating in the formation of metamorphic rock was first noted by the pioneering Scottish naturalist, James Hutton , who is often described as the father of modern geology. Hutton wrote in 1795 that some rock beds of the Scottish Highlands had originally been sedimentary rock but had been transformed by great heat. Hutton also speculated that pressure
6642-400: Is uncertain. Special classifications exist for metamorphic rocks with a volcaniclastic protolith or formed along a fault or through hydrothermal circulation . A few special names are used for rocks of unknown protolith but known modal composition, such as marble, eclogite , or amphibolite . Special names may also be applied more generally to rocks dominated by a single mineral, or with
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6804-426: Is used only when very little else is known about the rock that would allow a more definite classification. Textural classifications may be prefixed to indicate a sedimentary protolith ( para- , such as paraschist) or igneous protolith ( ortho- , such as orthogneiss). When nothing is known about the protolith, the textural name is used without a prefix. For example, a schist is a rock with schistose texture whose protolith
6966-475: Is usually devoid of schistosity and forms a tough, equigranular rock. If the rock was originally banded or foliated (as, for example, a laminated sandstone or a foliated calc- schist ) this character may not be obliterated, and a banded hornfels is the product. Contact metamorphism close to the surface produces distinctive low-pressure metamorphic minerals, such as spinel , andalusite, vesuvianite , or wollastonite . Similar changes may be induced in shales by
7128-470: Is very low in silica) to metafelsic-rock (with a high silica content). Where the mineral mode cannot be determined, as is often the case when rock is first examined in the field , then classification must be based on texture. The textural types are: A hornfels is a granofels that is known to result from contact metamorphism. A slate is a fine-grained metamorphic rock that easily splits into thin plates but shows no obvious compositional layering. The term
7290-528: The Appalachian Basin . During the Appalachian orogeny, these sediments became folded, faulted, and moved around. Only during the past few million years has the landscape we see today taken shape. The relatively softer or easily weathered rocks became valleys while the harder and erosion-resistant rocks became the mountain ridges. The development of this landscape continues to this day. Uplift of
7452-570: The Basin and Range Province of southwestern North America, but are also found in southern Aegean Sea , in the D'Entrecasteaux Islands , and in other areas of extension. Continental shields are regions of exposed ancient rock that make up the stable cores of continents. The rock exposed in the oldest regions of shields, which is of Archean age (over 2500 million years old), mostly belong to granite-greenstone belts. The greenstone belts contain metavolcanic and metasedimentary rock that has undergone
7614-865: The British in the Philadelphia campaign , the Continental Congress moved west, where it met at the Lancaster courthouse on Saturday, September 27, 1777, and then to York . In York, the Second Continental Congress adopted the Articles of Confederation , largely authored by Pennsylvania delegate John Dickinson, that formed 13 independent States into a new union. Later, the Constitution was written, and Philadelphia
7776-474: The Canadian province of Ontario to its northwest via Lake Erie . Pennsylvania was founded in 1681 through a royal land grant to William Penn , the son of the state's namesake . Prior to that, between 1638 and 1655, a southeast portion of the state was part of New Sweden , a Swedish Empire colony. Established as a haven for religious and political tolerance, the colonial-era Province of Pennsylvania
7938-594: The Catskill Formation are the predominant bedrock type in the Poconos. The elevation of the plateau is between 1,200 feet (366 m) and 2,300 feet (701 m) with only a few steep hills such as Camelback Mountain . Much of the rock sits in gently dipping horizontal beds, unlike the neighboring Appalachian Mountain section. Considered a part of the Pocono Plateau, this area lies to the north of
8100-746: The Commonwealth of Pennsylvania ( Pennsylvania Dutch : Pennsilfaani ), is a U.S. state spanning the Mid-Atlantic , Northeastern , Appalachian , and Great Lakes regions of the United States . It borders Delaware to its southeast, Maryland to its south, West Virginia to its southwest, Ohio and the Ohio River to its west, Lake Erie and New York to its north, the Delaware River and New Jersey to its east, and
8262-536: The Declaration of Independence the following year. On December 12, 1787, Pennsylvania was the second state to ratify the U.S. Constitution . In July 1863, the Battle of Gettysburg , fought over three days in and around Gettysburg , was the bloodiest and most decisive battle of the American Civil War , claiming over 50,000 Union and Confederate fatalities and repelling Robert E. Lee 's invasion of
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#17327880352748424-724: The Delaware River in the east and the Susquehanna River in central Pennsylvania. The second tribe, the Susquehannock , spoke an Iroquoian language and were based in Western Pennsylvania from New York state in the north to West Virginia in the southwest, including the Susquehanna, Allegheny , and Monongahela rivers near present-day Pittsburgh . European disease and constant warfare with several neighboring tribes and groups of Europeans weakened these two tribes, and they were grossly outpaced financially as
8586-482: The Delaware River to the east, 80°31' W to the west, and the 42° N to the north, except for a short segment on the western end where a triangle extends north to Lake Erie . The state has five geographical regions: Allegheny Plateau , Ridge and Valley , Atlantic Coastal Plain , Piedmont , and Erie Plain . Pennsylvania's diverse topography produces a variety of climates, though the entire state experiences cold winters and humid summers. Straddling two major zones,
8748-547: The Dominican Republic , China , Mexico , and Vietnam . Metamorphic rocks Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism . The original rock ( protolith ) is subjected to temperatures greater than 150 to 200 °C (300 to 400 °F) and, often, elevated pressure of 100 megapascals (1,000 bar ) or more, causing profound physical or chemical changes. During this process,
8910-884: The Hurons and Iroquois blocked them from proceeding west into Ohio during the Beaver Wars . As they lost numbers and land, the Hurons abandoned much of their western territory and moved closer to the Susquehanna River, and the Iroquois and Mohawk tribes moved further north. Northwest of the Allegheny River was the Iroquoian Petun , who were fragmented into three groups during the Beaver Wars:
9072-605: The Jurassic as the Atlantic Ocean began to form. Much of the rocks from this area have 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 . A small slice of Paleozoic rocks, mostly carbonates, exists in Buckingham Township . These rocks lie north of
9234-502: The Late Mississippian , forests of Lycopodiophyta , Arthrophyta , Pteridophyta , and Pteridospermatophyta began to grow in these plains. As the conditions became more favorable for the dense forests to survive for hundred of thousands of years, much of the dead plant material became preserved in oxygen -depleted environments. The accumulation of this material became preserved in the vast coal deposits. The rise and fall of
9396-614: The Maryland border. A few of the ridge tops contain some low-volatile bituminous coal fields including the Broad Top field. This region is also home to two national stories: the Quecreek Mine Rescue and the crash of United Airlines Flight 93 . Located in the southwest corner of the state, the Waynesburg hills are another major coal-producing area for the state. Much of the 64.4 billion tons of bituminous coal that
9558-453: The Mississippian Period came from highlands located to the southeast. Waves of mountain-building occasionally brought coarser-grained sediments onto the plain. As the mountains eroded, the sediments became more fine-grained. As the highlands became more distant, or eroded, the sands would grade into silt or clay. Since the North American Plate was near the equator, a tropical climate existed and allowed dense forests to flourish. Beginning in
9720-457: The Northeast megalopolis and is associated with the Northeastern United States . Pittsburgh is part of the Great Lakes megalopolis and is often associated with the Rust Belt . During the September 11, 2001, terrorist attacks on the United States , the small town of Shanksville, Pennsylvania , received worldwide attention after United Airlines Flight 93 crashed into a field in Stonycreek Township , located 1.75 miles (2.82 km) north of
9882-498: The Pennsylvania Dutch in southern Pennsylvania called the Great Valley A physiographic province, as are these section titles. Many of Pennsylvania's water gaps cut through Blue Mountain including Delaware Water Gap , Lehigh Gap , Schuylkill Gap , Susquehanna Gap , and Swatara Gap . Also along the ridge, many " wind gaps " also exist. The rocks of the Blue Mountain section include mostly Silurian aged sandstone, conglomerate , siltstone, shale, and some limestone. Blue mountain
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#173278803527410044-403: The Secretary of War under President Abraham Lincoln . Control of the machine was subsequently passed on to Cameron's son J. Donald Cameron , whose ineffectiveness resulted in a transfer of power to the more shrewd Matthew Quay and finally to Boies Penrose . The post-Civil War era, known as the Gilded Age , saw the continued rise of industry in Pennsylvania. Pennsylvania was home to some of
10206-485: The Spanish–American War . Pennsylvania was an important industrial center in World War I , and the state provided over 300,000 soldiers for the military. On May 31, 1918, the Pittsburgh Agreement was signed in Pittsburgh to declare the formation of the independent state of Czechoslovakia with future Czechoslovak president Tomáš Masaryk . In 1922, 310,000 Pennsylvania miners joined the UMW General coal strike , which lasted 163 days and shut down most coal mines within
10368-415: The United States . Pennsylvania has 51 miles (82 km) of coastline along Lake Erie and 57 miles (92 km) of shoreline along the Delaware Estuary . Of the original Thirteen Colonies , Pennsylvania is the only state that does not border the Atlantic Ocean . The boundaries of the state are the Mason–Dixon line (39°43' N) to the south, Twelve-Mile Circle on the Pennsylvania- Delaware border,
10530-445: The University of Pennsylvania in Philadelphia . The university, one of nine colonial colleges , was the first college established in Pennsylvania and one of the first in the nation. Today, it is an Ivy League university, which is routinely ranked among the world's best universities. Dickinson College in Carlisle , founded by Benjamin Rush and named after John Dickinson, was the first college founded after Revolutionary War and
10692-450: The atoms and ions in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact. Metamorphic rocks are characterized by their distinctive mineral composition and texture. Because every mineral is stable only within certain limits, the presence of certain minerals in metamorphic rocks indicates the approximate temperatures and pressures at which
10854-431: The county commission and freedom of religion , which were subsequently replicated in many of the Thirteen Colonies . What had been Upland on the Pennsylvania side of the Pennsylvania-Delaware border was renamed Chester County when Pennsylvania instituted its colonial governments on March 4, 1681. Penn signed a peace treaty with Tamanend , leader of the Lenape, which began a long period of friendly relations between
11016-402: The crystallization of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process. Metamorphic rocks are typically more coarsely crystalline than the protolith from which they formed. Atoms in the interior of a crystal are surrounded by a stable arrangement of neighboring atoms. This is partially missing at the surface of
11178-447: The seventh-largest metropolitan area in the country and one of the largest metropolitan areas in the world, and Pittsburgh is the center of the nation's 27th-largest metropolitan areas. As of 2020, the Lehigh Valley in eastern Pennsylvania is the nation's 69th-largest metropolitan area. Pennsylvania also has six additional metropolitan areas that rank among the nation's 200-most populous metropolitan areas. Philadelphia forms part of
11340-514: The 15th U.S. president and was the first president to be born in Pennsylvania. The Battle of Gettysburg , the major turning point of the American Civil War , took place near Gettysburg in July 1863. An estimated 350,000 Pennsylvanians served in the Union Army forces, including 8,600 African American military volunteers . The politics of Pennsylvania were for decades dominated by the financially conservative Republican -aligned Cameron machine , established by U.S. Senator Simon Cameron , later
11502-417: The 45th President of the United States Donald Trump occurred. Pennsylvania is 170 miles (274 km) north to south and 283 miles (455 km) east to west. Of a total 46,055 square miles (119,282 km ), 44,817 square miles (116,075 km ) are land, 490 square miles (1,269 km ) are inland waters, and 749 square miles (1,940 km ) are waters in Lake Erie . It is the 33rd-largest state in
11664-428: The 48 states. The Philadelphia Naval Shipyard served as an important naval base, and Pennsylvania produced important military leaders, including George C. Marshall , Hap Arnold , Jacob Devers , and Carl Spaatz . During the war, over a million Pennsylvanians served in the armed forces, and more Medals of Honor were awarded to Pennsylvanians than to individuals from any other state. The Three Mile Island accident
11826-516: The Americas began, at least two major Native American tribes inhabited Pennsylvania. The first, the Lenape , spoke an Algonquian language and inhabited the eastern region of the state, then known as Lenapehoking . It included most of present-day New Jersey and the Lehigh Valley and Delaware Valley regions in eastern and southeastern Pennsylvania. The Lenape's territory ended somewhere between
11988-686: The Commonwealth including the Grenville orogeny , the Taconic orogeny , the Acadian orogeny , and the Appalachian orogeny . The Appalachian event has left the most evidence and has continued to shape the landscape of the state. The Pennsylvania terrain has also been affected by continental rifting during the Mesozoic era . Pleistocene glaciers have also repeatedly visited the state over
12150-746: The Dutch began settling the Delmarva Peninsula by establishing the Zwaanendael Colony on the site of present-day Lewes, Delaware . In 1638, Sweden established the New Sweden Colony in the region of Fort Christina on the site of present-day Wilmington, Delaware . New Sweden claimed and, for the most part, controlled the lower Delaware River region, including parts of present-day Delaware, New Jersey, and Pennsylvania, but settled few colonists there. On March 12, 1664, King Charles II of England gave James, Duke of York
12312-456: The Earth's surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth's crust. Some examples of metamorphic rocks are gneiss , slate , marble , schist , and quartzite . Slate and quartzite tiles are used in building construction. Marble is also prized for building construction and as a medium for sculpture. On
12474-435: The Earth's surface, where they are subject to high temperatures and the great pressure of the rock layers above. They can also form from tectonic processes such as continental collisions, which cause horizontal pressure, friction, and distortion. Metamorphic rock can be formed locally when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior. The study of metamorphic rocks (now exposed at
12636-632: The Furlong fault which is an offshoot of the larger Chalfont fault. Buckingham Mountain rises south of the valley and comprises quartzite. The other ridge is less prominent and is underlain by the conglomerates of the Stockton Formation . Karst is a localized problem in this area. A small and fragmented province in northeastern Pennsylvania called the Reading Prong is akin to the crystalline bedrock found in much of New England . This
12798-480: The General Assembly refused to occupy the building. In 1901, political and popular indignation prompted a second contest that was restricted to Pennsylvania architects; Joseph Miller Huston of Philadelphia was chosen to design the present Pennsylvania State Capitol that incorporated Cobb's building into a magnificent public work, finished and dedicated in 1907. James Buchanan , a Franklin County native, served as
12960-596: The Netherlands confirmed the English conquest on July 21, 1667, although there were temporary reversions. On September 12, 1672, during the Third Anglo-Dutch War , the Dutch reconquered New York Colony / New Amsterdam , establishing three County Courts, which went on to become original Counties in present-day Delaware and Pennsylvania. The one that later transferred to Pennsylvania was Upland. This
13122-741: The New England Province, the Ridge and Valley Province , the Appalachain Province , and the Central Lowlands Province. A majority of the rocks in Pennsylvania exposed at the surface are sedimentary and were deposited during the Paleozoic Era . Almost all of the metamorphic and igneous rocks are confined to the southeast portion of the state. A total of four orogenies have affected the rocks of
13284-654: The North, leading to the Union's preservation . Throughout the late 19th and 20th centuries, the state's manufacturing-based economy contributed to the development of much of the nation's early infrastructure, including key bridges, skyscrapers , and military hardware used in U.S.-led victories in World War I , World War II , and the Cold War . Pennsylvania's geography is highly diverse. The Appalachian Mountains run through
13446-834: The Petun of New York, the Wyandot of Ohio, and the Tiontatecaga of the Kanawha River in southern West Virginia. South of the Allegheny River was a nation known as Calicua, which may have been part of the Monongahela culture . In the 17th century, the Dutch and the English each claimed both sides of the Delaware River as part of their colonial lands in America. The Dutch were the first to take possession. By June 3, 1631,
13608-649: 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 Big Bushkill Creek 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
13770-804: The Quakers and the Indians. Additional treaties between Quakers and other tribes followed. The Treaty of Shackamaxon of William Penn was never violated. Between 1730 and when the Pennsylvania Colony was shut down by Parliament with the Currency Act in 1764, the Pennsylvania Colony made its own paper money to account for the shortage of actual gold and silver. The paper money was called Colonial Scrip . The Colony issued bills of credit, which were as good as gold or silver coins because of their legal tender status. Since they were issued by
13932-471: The Taconic orogeny, more igneous intrusions and metamorphism occurred as the ancestral Taconic Mountains were pushed up. The sediments that were deposited in a sea between an island-arc and the Iapetus eventually were squeezed and deformed along a subduction zone. The sediments deposited in that sea are now located in the Great Valley section. (See below) The sediments placed from the rifting of Rodinia became
14094-624: The abrupt escarpment that divides the Ridge and Valley Province 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. The Allegheny Front reaches its highest elevation in Pennsylvania at Blue Knob , 3,136 feet (956 m), an unusual bulge along this symmetrical ridgeline. Streams that cut into the ridge are often shallow and steep. This section includes Pennsylvania's highest point, Mount Davis , which stands at 3,213 feet (979 m) above sea level. Many of
14256-482: The amphibolite or granulite facies. These form most of the exposed rock in Archean cratons. The granite-greenstone belts are intruded by a distinctive group of granitic rocks called the tonalite - trondhjemite - granodiorite or TTG suite. These are the most voluminous rocks in the craton and may represent an important early phase in the formation of continental crust. Mid-ocean ridges are where new oceanic crust
14418-404: The bands showing the colors of the minerals that formed them. Foliated rock often develops planes of cleavage . Slate is an example of a foliated metamorphic rock, originating from shale , and it typically shows well-developed cleavage that allows slate to be split into thin plates. The type of foliation that develops depends on the metamorphic grade. For instance, starting with a mudstone ,
14580-557: The bedrock for this area. The oldest exposed rocks in Pennsylvania are found here and consist of the Baltimore Gneiss . These rocks have a complex history and a vast array of different minerals. They are similar in many respects to their cousins in northern and central Maryland , immediately to the south. Much of the rock was altered during the formation of Rodinia during the Grenville orogeny. These rocks eventually provided
14742-420: The bulk composition of a rock. Hot fluids circulating through pore space in the rock can dissolve existing minerals and precipitate new minerals. Dissolved substances are transported out of the rock by the fluids while new substances are brought in by fresh fluids. This can obviously change the mineral makeup of the rock. However, changes in the mineral composition can take place even when the bulk composition of
14904-399: The burning of coal seams. This produces a rock type named clinker . There is also a tendency for metasomatism between the igneous magma and sedimentary country rock, whereby the chemicals in each are exchanged or introduced into the other. In that case, hybrid rocks called skarn arise. Dynamic (cataclastic) metamorphism takes place locally along faults . Here intense shearing of
15066-543: The center of the state; the Allegheny and Pocono mountains span much of Northeastern Pennsylvania ; close to 60% of the state is forested . While it has no ocean shoreline, it has 140 miles (225 km) of waterfront along Lake Erie and the tidal Delaware River. Pennsylvania is the fifth-most populous state in the United States , with over 13 million residents as of the 2020 United States census . The state
15228-435: The circulation of fluids through buried rock, to the list of processes that help bring about metamorphism. However, metamorphism can take place without metasomatism ( isochemical metamorphism ) or at depths of just a few hundred meters where pressures are relatively low (for example, in contact metamorphism ). Metamorphic processes change the texture or mineral composition of the metamorphosed rock. Metasomatism can change
15390-429: The city's population as of 2000. In the 20th century, as Pennsylvania's historical national and even global leadership in mining largely ceased and its steelmaking and other heavy manufacturing sectors slowed, the state sought to grow its service and other industries to replace the jobs and economic productivity lost from the downturn of these industries. Pittsburgh's concentration of universities has enabled it to be
15552-722: The coastal plain is the Fall Line . The coastal plain in Pennsylvania was once home to thousands of acres of fresh water tidal marsh . This was important in the early development 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
15714-427: The collision of tectonic plates at convergent boundaries . Here formerly deeply buried rock has been brought to the surface by uplift and erosion. The metamorphic rock exposed in orogenic belts may have been metamorphosed simply by being at great depths below the Earth's surface, subjected to high temperatures and the great pressure caused by the immense weight of the rock layers above. This kind of regional metamorphism
15876-491: The contact area to unmetamorphosed (unchanged) country rock some distance away. The formation of important ore minerals may occur by the process of metasomatism at or near the contact zone. Contact aureoles around large plutons may be as much as several kilometers wide. The term hornfels is often used by geologists to signify those fine grained, compact, non-foliated products of contact metamorphism. The contact aureole typically shows little deformation, and so hornfels
16038-612: The crystal, producing a surface energy that makes the surface thermodynamically unstable. Recrystallization to coarser crystals reduces the surface area and so minimizes the surface energy. Although grain coarsening is a common result of metamorphism, rock that is intensely deformed may eliminate strain energy by recrystallizing as a fine-grained rock called mylonite . Certain kinds of rock, such as those rich in quartz, carbonate minerals , or olivine, are particularly prone to form mylonites, while feldspar and garnet are resistant to mylonitization. Many kinds of metamorphic rocks show
16200-614: The development of labor unions helped them gain living wages. However, the rise of unions also led to a rise of union busting with several private police forces springing up. Pennsylvania was the location of the first documented organized strike in North America, and Pennsylvania was the location of two hugely prominent strikes, the Great Railroad Strike of 1877 and the Coal Strike of 1902 . The eight-hour day
16362-484: The earliest known signs of human activity in Pennsylvania and perhaps all of North America, including the remains of a civilization that existed over 10,000 years ago and possibly pre-dated the Clovis culture . By 1000 CE, in contrast to their nomadic hunter-gatherer ancestors , the native population of Pennsylvania had developed agricultural techniques and a mixed food economy. By the time European colonization of
16524-423: The eclogite facies releases a great deal of water vapor from the rock, which drives volcanism in the overlying volcanic arc . Eclogite is also significantly denser than blueschist, which drives further subduction of the slab deep into the Earth's mantle . Metabasalt and blueschist may be preserved in blueschist metamorphic belts formed by collisions between continents. They may also be preserved by obduction onto
16686-417: The fifth and currently the sixth-largest city after decades of being among the top three. After 1990, as information-based industries became more important in the economy, state and local governments put more resources into the old, well-established public library system. Some localities, however, used new state funding to cut local taxes. New ethnic groups, especially Hispanics and Latinos , began entering
16848-577: The first. At the time, Pennsylvania was the most ethnically and religiously diverse of the thirteen colonies. Because a third of Pennsylvania's population spoke German , the Constitution was presented in German so those citizens could participate in the discussion about it. Reverend Frederick Muhlenberg , a Lutheran minister and the first Speaker of the U.S. House of Representatives , acted as chairman of Pennsylvania's ratifying convention. For half
17010-437: The following sequence develops with increasing temperature: The mudstone is first converted to slate, which is a very fine-grained, foliated metamorphic rock, characteristic of very low grade metamorphism. Slate in turn is converted to phyllite , which is fine-grained and found in areas of low grade metamorphism. Schist is medium to coarse-grained and found in areas of medium grade metamorphism. High-grade metamorphism transforms
17172-648: The foundation of the colonial Province of Pennsylvania in 1681. Archaeologists believe the first settlement of the Americas occurred at least 15,000 years ago, during the Last Glacial Period , though it is unclear when humans first inhabited present-day Pennsylvania. Between 10,000 and 16,000 years ago, Native Americans crossed the two continents, arriving in North America . Meadowcroft Rockshelter in Jefferson Township includes
17334-571: The government and not a banking institution, they were interest-free, largely defraying the expense of the government and therefore taxation of the people. It also promoted general employment and prosperity, since the government used discretion and did not issue excessive amounts that inflated the currency. Benjamin Franklin had a hand in creating this currency, whose utility, he said, was never to be disputed. The currency also met with "cautious approval" by Adam Smith . In 1740, Franklin also founded
17496-449: The identical composition, Al 2 SiO 5 . Likewise, forsterite is stable over a broad range of pressure and temperature in marble , but is converted to pyroxene at elevated pressure and temperature in more silicate-rich rock containing plagioclase , with which the forsterite reacts chemically. Many complex high-temperature reactions may take place between minerals without them melting, and each mineral assemblage produced indicates
17658-836: 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. Despite this, Celestine was proposed as the state mineral in 2002. The proposal however, was not approved by the state legislature. Pennsylvania is also home to the famous Drake Oil Well in Titusville which helped give rise to the modern oil industry and two brand name motor oils, Quaker State (now owned by Royal Dutch Shell) and Pennzoil . Pennsylvania also has reserves of natural gas from both deeply buried source rocks and coal-bed areas. One of
17820-433: The land be called New Wales, but there were objections to that name, so he recommended Sylvania (from the Latin silva : "forest, woods"). The King named it Pennsylvania (literally "Penn's Woods") in honor of Admiral Penn. The younger Penn was embarrassed at this name, fearing that people would think he had named it after himself, but King Charles would not rename the grant. Penn established a government with two innovations,
17982-567: The largest chocolate manufacturer in North America. Heinz Company was also founded during this period. These huge companies exercised a large influence on the politics of Pennsylvania; as Henry Demarest Lloyd put it, oil baron John D. Rockefeller "had done everything with the Pennsylvania legislature except refine it". Pennsylvania created a Department of Highways and engaged in a vast program of road-building, while railroads continued to see heavy usage. The growth of industry eventually provided middle class incomes to working-class households after
18144-587: The largest steel companies in the world. Andrew Carnegie founded the Carnegie Steel Company in Pittsburgh and Charles M. Schwab founded Bethlehem Steel in Bethlehem . Other titans of industry, including John D. Rockefeller and Jay Gould , also operated in Pennsylvania. In the latter half of the 19th century, the U.S. oil industry was born in Western Pennsylvania , which supplied
18306-450: The last 100,000 years. These glaciers have left some evidence and carved out much of the landscape of the northern tier of the state. A rock with high economic value from Pennsylvania is anthracite coal . Before mining began, there was an estimated 22.8 billion tons of anthracite in Pennsylvania. In 2001, 12 billion tons still remained in the ground, most of which was not economically feasible to mine. American geologists recognized
18468-437: The low-pressure facies, such as the hornfels and sanidinite facies . Most metamorphic rock is formed by regional metamorphism in the middle and lower crust, where the rock reaches the higher-pressure metamorphic facies. This rock is found at the surface only where extensive uplift and erosion has exhumed rock that was formerly much deeper in the crust. Metamorphic rock is extensively exposed in orogenic belts produced by
18630-417: The majority of the state, except for the southeastern corner, has a humid continental climate ( Köppen climate classification Dfb ). The southern portion of the state has a humid subtropical climate. The largest city, Philadelphia , has a humid subtropical climate (Köppen Cfa ). Summers are generally hot and humid. Moving toward the mountainous interior of the state, the winter climate becomes colder,
18792-504: The mountains are long and broad with relatively 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 dendritic 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 4.5 miles (7 km) from
18954-491: The mountains, along with changes in sea level, occurred numerous times (often in conjunction). These cyclical stratagraphic events sequences are preserved in the rock record and are often called cyclothems . By the Late Permian , much of the continental plate collision had subsided; the mountain building however, still continued. All of the sediments deposited during the previous 30 million years became folded and faulted as
19116-442: The north-central region with York , Carlisle , and the state capital Harrisburg on the Susquehanna River in the east-central region of the state. Altoona and Johnstown are in the state's west-central region. The state's three-most populated cities, in order of size, are Philadelphia, Pittsburgh, and Allentown. As of the 2020 U.S. census , Pennsylvania had a population of 13,011,844, up from 12,702,379 in 2010. Pennsylvania
19278-627: The number of cloudy days increases, and snowfall amounts are greater. Western areas of the state, particularly locations near Lake Erie , can receive over 100 inches (250 cm) of snowfall annually, and the entire state receives plentiful precipitation throughout the year. The state may be subject to severe weather from spring through summer into autumn. Tornadoes occur annually in the state, sometimes in large numbers, such as 30 recorded tornadoes in 2011; generally speaking, these tornadoes do not cause significant damage. Cities in Pennsylvania include Philadelphia , Reading , Lebanon , and Lancaster in
19440-654: The old Dauphin County Court House until December 1821 when the Federal -style Hills Capitol, named for Lancaster architect Stephen Hills , was constructed on a hilltop land grant of four acres set aside for a seat of state government in Harrisburg by the son and namesake of John Harris, Sr. , a Yorkshire native who founded a trading post and ferry on the east shore of the Susquehanna River in 1705. The Hills Capitol burned down on February 2, 1897, during
19602-453: The other hand, schist bedrock can pose a challenge for civil engineering because of its pronounced planes of weakness. Metamorphic rocks form one of the three great divisions of rock types. They are distinguished from igneous rocks , which form from molten magma , and sedimentary rocks , which form from sediments eroded from existing rock or precipitated chemically from bodies of water. Metamorphic rocks are formed when existing rock
19764-460: The overriding plate as part of ophiolites . Eclogites are occasionally found at sites of continental collision, where the subducted rock is rapidly brought back to the surface, before it can be converted to the granulite facies in the hot upper mantle. Many samples of eclogite are xenoliths brought to the surface by volcanic activity. Many orogenic belts contain higher-temperature, lower-pressure metamorphic belts. These may form through heating of
19926-673: The platform for the deposition of sediment that would become the Wissahickon Formation during a rifting of Rodinia. Sea floor spreading continued until a passive margin developed along the new Iapetus Ocean and a beach strandline developed. These sediments eventually became the Chickies Formation . Siliclasitc and carbonate deposition continued through the Cambrian and into the Ordovician period. During
20088-488: The province and they are listed below. Much of the drainage patterns in the province is trellis . South Mountain is the northern tip of the Blue Ridge Mountains . This region is characterized by broad flat ridges with deep narrow valleys. The rocks here are highly metamorphosed igneous and sedimentary rocks with some occasional dolomite . These rocks are Pre-Cambrian in age. The Great Appalachian Valley
20250-563: The province has caused rivers to cut water gaps through the mountain ranges, and has continuously presented new softer rocks in the valleys to be eroded away. This is by far the largest province in the state, and most of the rocks in this region are not folded and faulted and sit relatively flat. However, parts of the Appalachian Plateau appear to be mountainous due to erosion caused by streams and glaciers. In western Pennsylvania, large bituminous coal fields exist in rocks with
20412-429: The remainder from Africa (5%), North America (3.1%), and Oceania (0.4%). The state's largest ancestry groups, expressed as a percentage of total people who responded with a particular ancestry for the 2010 census, were German 28.5%, Irish 18.2%, Italian 12.8%, African Americans 9.6%, English 8.5%, Polish 7.2%, and French 4.2%. As of 2018, the top countries of origin for Pennsylvania's immigrants were India ,
20574-550: The ridgelines to its north and west, is one of a series of near parallel ridges that run for tens of miles, and are equally likely to be called Ridge or Mountain. Hence Blue Mountain is not to be confused with the Blue Ridge Mountains but instead, represents the sharp escarpment , a step in elevation separating the Appalachian Mountains from the pastoral basin famous as the landscape associated with
20736-475: The rock by ascending magmas of volcanic arcs, but on a regional scale. Deformation and crustal thickening in an orogenic belt may also produce these kinds of metamorphic rocks. These rocks reach the greenschist , amphibolite, or granulite facies and are the most common of metamorphic rocks produced by regional metamorphosis. The association of an outer high-pressure, low-temperature metamorphic zone with an inner zone of low-pressure, high-temperature metamorphic rocks
20898-421: The rock does not change. This is possible because all minerals are stable only within certain limits of temperature, pressure, and chemical environment. For example, at atmospheric pressure, the mineral kyanite transforms to andalusite at a temperature of about 190 °C (374 °F). Andalusite, in turn, transforms to sillimanite when the temperature reaches about 800 °C (1,470 °F). All three have
21060-458: The rock remains mostly in the solid state, but gradually recrystallizes to a new texture or mineral composition. The protolith may be an igneous , sedimentary , or existing metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by their protolith, their chemical and mineral makeup, and their texture . They may be formed simply by being deeply buried beneath
21222-423: The rock to gneiss , which is coarse to very coarse-grained. Rocks that were subjected to uniform pressure from all sides, or those that lack minerals with distinctive growth habits, will not be foliated. Marble lacks platy minerals and is generally not foliated, which allows its use as a material for sculpture and architecture. Metamorphic rocks are one of the three great divisions of all rock types, and so there
21384-495: The rock typically forms mylonites. Impact metamorphism is unlike other forms of metamorphism in that it takes place during impact events by extraterrestrial bodies. It produces rare ultrahigh pressure metamorphic minerals, such as coesite and stishovite . Coesite is rarely found in eclogite brought to the surface in kimberlite pipes , but the presence of stishovite is unique to impact structures. Slate tiles are used in construction, particularly as roof shingle. Quartzite
21546-407: The rock underwent metamorphism. These minerals are known as index minerals . Examples include sillimanite , kyanite , staurolite , andalusite , and some garnet . Other minerals, such as olivines , pyroxenes , hornblende , micas , feldspars , and quartz , may be found in metamorphic rocks but are not necessarily the result of the process of metamorphism. These minerals can also form during
21708-486: The rock). Metasedimentary rocks are divided into carbonate-rich rock (metacarbonates or calcsilicate-rocks) or carbonate-poor rocks, and the latter are further classified by the relative abundance of mica in their composition. This ranges from low-mica psammite through semipelite to high-mica pelite . Psammites composed mostly of quartz are classified as quartzite. Metaigneous rocks are classified similarly to igneous rocks, by silica content, from meta-ultramafic-rock (which
21870-468: The roots of the ancestral Taconics and went through their first wave of metamorphism during the Taconic orogeny. Additional waves of metamorphism continued up until the Alleghanian orogeny. The lowlands are underlain primarily by more easily eroded rocks such as limestone , dolomite , and phyllite . These rocks are relatively younger in age than the surrounding uplands and are likely the result of
22032-406: The sedimentary rock limestone and chalk change into larger crystals in the metamorphic rock marble . In metamorphosed sandstone, recrystallization of the original quartz sand grains results in very compact quartzite, also known as metaquartzite, in which the often larger quartz crystals are interlocked. Both high temperatures and pressures contribute to recrystallization. High temperatures allow
22194-443: The smallest physiographic provinces in the state is confined to Philadelphia , Delaware , and Bucks counties along the Delaware River . Local relief is less than 200 feet (61 m) and much of the bedrock is buried under recent alluvial deposits. On the geologic map, "Trenton Gravel" is used to describe most of these sediments. Much of the alluvial sediments that exist here are sand, silt, and clays. The traditional boundary of
22356-576: The source area was relatively close and deposited in a moist climate. These sediments grade into finer reddish sands and silts, (Bloomsburg Formation) as the source area became more distant and/or less productive. The climate during this time was drier. Arguably the most complex and most studied section in the Pennsylvania . The state's Ridge and Valley province is home to one of Pennsylvania's most profitable coal fields in history, containing high-grade anthracite coal. The sediments deposited during
22518-404: The southeast, Pittsburgh in the southwest, and the tri-cities of Allentown , Bethlehem , and Easton in the central east, known as the Lehigh Valley . The northeast includes the former anthracite coal mining cities of Scranton , Wilkes-Barre , Pittston , Nanticoke , and Hazleton . Erie is located in the northwest. State College is located in the central region. Williamsport is in
22680-423: The southern and middle anthracite fields, the anthracite valley has been recently glaciated repeatedly. This action has left many talus slopes at the base of Moosic Mountains , and the soils often contain large boulders that make excavation difficult. 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
22842-579: 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 valleys and rarely cuts across the ridges. The Pennsylvania Turnpike used tunnels cut through the ridges rather than scaling the mountain tops. Mount Nittany , Tuscarora Mountain , Jacks Mountain , Wills Mountain , and Sideling Hill are five prominent mountains in this section. The section contains Cambrian- through Pennsylvanian-aged sediments all deposited into
23004-581: The state to fill low-skill jobs in agriculture and service industries. For example, in Chester County , Mexican immigrants brought the Spanish language , increased Catholicism , high birth rates, and cuisine when they were hired as agricultural laborers; in some rural localities, they made up half or more of the population. Stateside Puerto Ricans built a large community in the state's third-largest city, Allentown , where they comprise over 40% of
23166-827: The state. In 1923, President Calvin Coolidge established the Allegheny National Forest under the authority of the Weeks Act of 1911. The forest is located in the northwest part of the state in Elk , Forest , McKean , and Warren Counties for the purposes of timber production and watershed protection in the Allegheny River basin. The Allegheny is the state's only national forest. Pennsylvania manufactured 6.6 percent of total U.S. military armaments produced during World War II , ranking sixth among
23328-601: The state." The ensuing hostilities became known as Pontiac's War . After the Stamp Act Congress of 1765, delegate John Dickinson of Philadelphia wrote the Declaration of Rights and Grievances . The Congress was the first meeting of the Thirteen Colonies , which convened at the request of the Massachusetts assembly; nine of the 13 colonies sent delegates. Dickinson then wrote Letters from
23490-556: 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 Jurassic Period) None of the mountains in this section rise above 1,700 feet (518 m) and the river valley is as low as 250 feet (76 m). Standard long, narrow, and steep-sided ridges with narrow valleys define
23652-592: The supercontinent Pangea was finally formed. It would take 150 million years for the mountains of this area to achieve the shapes seen today. These mountains are steep-sided and valleys are canoe-shaped, largely due to the area's complex folded structure. Most of the coal being mined from this section is from the Pennsylvanian-aged formations. Along with the Mazon Creek fossil field in Illinois ,
23814-404: The temperatures and pressures at the time of metamorphism. These reactions are possible because of rapid diffusion of atoms at elevated temperature. Pore fluid between mineral grains can be an important medium through which atoms are exchanged. The change in the particle size of the rock during the process of metamorphism is called recrystallization . For instance, the small calcite crystals in
23976-549: The town. All 40 civilians and 4 Al-Qaeda hijackers on board were killed. The hijackers had intended to crash the plane into either the United States Capitol or The White House . After learning from family members via air phone of the earlier attacks on the World Trade Center , however, Flight 93's passengers revolted against the hijackers and fought for control of the plane, causing it to crash. It
24138-426: The unification of the states. Established in 1773, it was ratified on September 9, 1783, five days after the Treaty of Paris . James Smith wrote that in 1763, "the Indians again commenced hostilities, and were busily engaged in killing and scalping the frontier inhabitants in various parts of Pennsylvania. This state was then a Quaker government, and at the first of this war the frontiers received no assistance from
24300-451: The use of granulite as a classification for rock metamorphosed to the granulite facies. Instead, such rock will often be classified as a granofels. However, this approach is not universally accepted. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. The lower continental crust is mostly metamafic-rock and pelite which have reached the granulite facies . The middle continental crust
24462-462: The vast majority of kerosene for years thereafter. As the Pennsylvania oil rush developed, Pennsylvania's oil boom towns, such as Titusville , rose and later fell. Coal mining, primarily in the state's Coal Region in the northeast region of the state, also was a major industry for much of the 19th and 20th centuries. In 1903, Milton S. Hershey began construction on a chocolate factory in Hershey, Pennsylvania ; The Hershey Company grew to become
24624-511: The zonal schemes, based on index minerals, that were pioneered by the British geologist, George Barrow . The metamorphic facies is not usually considered when classifying metamorphic rock based on protolith, mineral mode, or texture. However, a few metamorphic facies produce rock of such distinctive character that the facies name is used for the rock when more precise classification is not possible. The chief examples are amphibolite and eclogite . The British Geological Survey strongly discourages
24786-550: Was eventually adopted, and the coal and iron police were banned. At the beginning of the 20th century, Pennsylvania's economy centered on steel production, logging , coal mining , textile production, and other forms of industrial manufacturing . A surge in immigration to the U.S. during the late 19th and early 20th centuries provided a steady flow of cheap labor for these industries, which often employed children and people who could not speak English from Southern and Eastern Europe . Thousands of Pennsylvanians volunteered during
24948-419: Was important in metamorphism. This hypothesis was tested by his friend, James Hall , who sealed chalk into a makeshift pressure vessel constructed from a cannon barrel and heated it in an iron foundry furnace. Hall found that this produced a material strongly resembling marble , rather than the usual quicklime produced by heating of chalk in the open air. French geologists subsequently added metasomatism ,
25110-477: Was known for its relatively peaceful relations with native tribes, innovative government system , and religious pluralism . Pennsylvania played a vital and historic role in the American Revolution and the ultimately successful quest for independence from the British Empire , hosting the First and Second Continental Congress in Philadelphia , which formed the Continental Army and appointed George Washington as its commander in 1775, and unanimously adopted
25272-474: Was not covered by the Late Wisconsinan glacier , but there is evidence of pre-Wisconsinan glaciers in the area. Along with the Endless Mountains, it is one of the most remote places in the eastern United States. This section has been influenced by glaciers and many of the valleys cut into the bedrock trend northwestward- in the direction of the retreating glaciers. There are many signs of glaciers including kames , eskers , kettles , and moraines . This section
25434-476: Was not yet in British possession, but the sale boxed in the portion of New Netherland on the West side of the Delaware River. The British conquest of New Netherland began on August 29, 1664, when New Amsterdam was coerced to surrender while facing cannons on British ships in New York Harbor . The conquest was completed in October 1664, when the British captured Fort Casimir in what today is New Castle, Delaware . The Treaty of Breda between England, France, and
25596-407: Was once again chosen to be cradle to the new nation. The Constitution was drafted and signed at the Pennsylvania State House in Philadelphia, now known as Independence Hall , the same building where the Declaration of Independence was previously adopted and signed in 1776. On December 12, 1787, Pennsylvania was the second state to ratify the U.S. Constitution , five days after Delaware became
25758-419: Was partially reversed on February 9, 1674, when the Treaty of Westminster ended the Third Anglo-Dutch War and reverted all political situations to the status quo ante bellum . The British retained the Dutch Counties with their Dutch names. By June 11, 1674, New York reasserted control over the outlying colonies, including Upland, and the names started to be changed to British names by November 11, 1674. Upland
25920-439: Was partitioned on November 12, 1674, producing the general outline of the current border between Pennsylvania and Delaware. On February 28, 1681, Charles II granted a land charter to Quaker leader William Penn to repay a debt of £16,000 (around £2,100,000 in 2008, adjusting for retail inflation) owed to William's father. The transaction represents one of the largest land grants to an individual in history. Penn proposed that
26082-441: Was the most significant nuclear accident in U.S. commercial nuclear power plant history. The state was hard-hit by the decline and restructuring of the steel industry and other heavy industries during the late 20th century. With job losses came heavy population losses, especially in the state's largest cities. Pittsburgh lost its place among the top ten most populous cities in the United States by 1950, and Philadelphia dropped to
26244-497: Was the only one of the four aircraft hijacked that day that never reached its intended target and the heroism of the passengers has been commemorated. Since 2003, the Tekko anime convention has been held annually in Pittsburgh. In October 2018, the Tree of Life – Or L'Simcha Congregation , a conservative Jewish synagogue, experienced the Pittsburgh synagogue shooting , which resulted in 11 fatalities. On July 13, 2024, near Butler, Pennsylvania , an assassination attempt on
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