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Pennsylvania Geography: The Land
Pennsylvania is one of the Mid-Atlantic states. It is known as the Keystone State because it is geographically in the center of the "arch" formed by the original 13 states. Six are located to the north and six to the south. Pennsylvania's width is 312 miles. The distance between its northern and southern boundaries is 158 miles. It is America's 33rd largest state.
The Allegheny Mountains run diagonally from the southwest to the northeast with piedmont and coastal plains in the southeast triangle. The Allegheny Front, as it's called, cuts a diagonal line across the state. In the northwest, the plateau falls to the Lake Erie lowlands and, finally, Lake Erie.
Pennsylvania is made up of these Physiographic Areas
The Allegheny Plateau covers much of west-central Pennsylvania, the southern tier of New York to the base of the Adirondack Mt., and a portion of northeast Ohio. This area consists primarily of extensively forested uplands, including the Catskill Mountains in NY, Pocono Mountains in PA, and Allegheny National Forest in both states. This is a transitional area dominated by oak-hickory forests towards the south and beech-maple forests towards the north. White pine and hemlocks also are an important component of the forests, more so historically. Small but important patches of spruce-fir forest occur on the Catskill High Peaks and at a few sites in northeastern PA. Several major river valleys dissect the highlands, and the Finger Lakes of central NY drain the northern portion of the physiographic area towards Lake Ontario. Roughly 70% of this area is forested today, with agriculture dominating primarily at lower elevations in western New York, the Susquehanna River valley, and in Ohio.
The eastern border of the Piedmont is the fall line, where resistant volcanic rock gives way to the sands and clays of the Coastal Plain. To the west, the Piedmont ends with the edge of the higher and more rugged Blue Ridge and Ridge and Valley regions of the Appalachian Mountains The Mid-Atlantic Piedmont is arbitrarily separated from the Southern Piedmont at the North Carolina-Virginia line, and extends north through Virginia, Maryland, and Pennsylvania before terminating in northern New Jersey. The rolling topography of the Piedmont formerly supported an extensive hardwood forest, with an oak-hickory type predominant in southern portions and Appalachian oak to the north. Large areas in the Virginia portion were dominated by Loblolly-shortleaf pine or pine-oak forests. Today, roughly 45% of the physiographic area is forested, and about an equal portion is in agricultural production. The remainder is experiencing rapid urbanization, especially in the vicinity of Washington D.C. and Philadelphia.
Northern Ridge and Valley
The Northern Ridge and Valley extends from southeastern Pennsylvania, through northwestern New Jersey and southeastern New York nearly to the base of the Adirondack Mts. It includes portions of several major river valleys, including the Hudson, Delaware, and Susquehanna Rivers. Ecologically, this is a transitional area, with forested ridges grading from primarily oak-hickory forests in the south to northern hardwood forests further north. Pine-oak woodlands and barrens and hemlock ravine forests are also important along ridges, whereas bottomland and riparian forests are important in the valleys, which are now largely cleared for agricultural and urban development. Roughly 50% of the physiographic area is forested today, the vast majority occurring at higher elevations. About 40% of the area is in agricultural production, primarily a mixture of dairy pastureland and corn. Over 200,000 ha is state forest land in PA and NJ; other important public lands include High Point State Park (NJ) and Wallkill National Wildlife Refuge.
Landforms within the Ohio Hills consist primarily of dissected, unglaciated plateaus ranging in elevation from 150 m to 450 m, with some valleys as low as 100 m and some mountainous areas reaching 1,100 m. A majority of the planning unit was dominated historically by oak-hickory forests; today these cover roughly 4.3 million ha (10.7 million ac), or 54% of the physiographic area. Numerous patches of northern hardwood forest occur on north-facing hillsides, particularly near the edges of the Allegheny Mountains in West Virginia and Allegheny Plateau in Ohio. Historically, oak-hickory and oak-pine regeneration was dependent on fire, and recent policies of fires suppression in the southern Appalachians has had major (primarily negative) effects on native forest composition and structure. Human populations are relatively sparse through most the physiographic area and are largely confined to the larger valleys; Pittsburgh, PA and Morgantown, WV are the largest cities. Roughly 40% of the physiographic area is in agricultural production or urban development, mostly in the northern half. Timber extraction has been a major activity throughout the history of this region, and it continues to be important on both public (10% of area) and privately owned forest lands. Extraction of minerals, oil and gas, and coal are also important land uses throughout this region, with a new wave of mining underway in the form of highly destructive mountaintop removal.
Pennsylvania Landscape and Landforms:
Atlantic Coastal Plain
This region runs across the southeastern corner of the state. A flat low area that falls to sea level where it meets the Delaware River.
This area is some of the richest farmland in the state consists of an area of low hills, ridges and valleys. It is located in the southeastern part of the state.
Appalachian Ridge and Valley Region
This area consists of a series of fertile valleys and long parallel ridges that are part of the Appalachian Mountain range. This region arcs from the south-central border with Maryland to the eastern border with New Jersey.
The Blue Ridge runs north form the south-central border. The Gettysburg National Park and the Southern Mountain are located in this area.
The Appalachian Plateau is the largest geographic region in the state. Mount Davis (the state's highest point) is 3,213 feet and is in this area. The Appalachian Plateau is located in the northern and western part of the state.
This is a flat region once covered by the waters of Lake Erie. This area covers the extreme northwestern corner of Pennsylvania.
Geography (from Greek γεωγραφία, geographia, lit. "earth description") is a field of science dedicated to the study of the lands, the features, the inhabitants, and the phenomena of the Earth.