Ridge-and-Valley Appalachians

The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian Highlands division. The physiographic province is divided into three sections, the Hudson Valley, the Central, and the Tennessee. [1]

Valley and Ridge province as part of the Appalachian Highlands division using the USGS physiographic classification

The river valleys were areas of indigenous settlements for thousands of years. In the historic period, the Cherokee people had towns along many of the rivers in western South Carolina and North Carolina, as well as on the western side of the Appalachian Mountains in present-day Tennessee. Similarly, the Catawba people occupied areas along the upper Catawba River in Western North Carolina, to the east of Cherokee County.

The ridge and valley system presents an important obstacle to east–west land travel even with today's technology. It was a nearly insurmountable barrier to European-American migrants who walked or rode horses traveling west to settle the Ohio Country, and later the Northwest Territory and Oregon Country. In the era when animal power dominated transportation, there was no safe way to cross east–west in the middle of the range; crossing was only possible nearer its extremes except for a few rough passages opened mid-range during the colonial era, such as Cumberland Gap, Braddock's Road and Forbes Road.

These were later improved as America's first National Roads, including Wilderness Road, Cumberland Road, Lincoln Highway, designated as U.S. Route 40 and U.S. Route 30 in later years. Early settlers of Ohio Country tended to enter it via the Ohio River; river systems were the most important transportation corridors. It was difficult in the late 19th and 20th centuries to construct railroads and modern highways through this area.

Geography
Valley and Ridge province of the Appalachian Highlands and its three physiographic sections: the Hudson, the Central, and the Tennessee Rivers

The eastern head of the Ridge and Valley region is marked by the Great Appalachian Valley, which lies just west of the Blue Ridge. The western side of the Ridge and Valley region is marked by steep escarpments such as the Allegheny Front, the Cumberland Mountains, and Walden Ridge. The Valley and Ridge is located on the west side of the Blue Ridge Mountains.

An aerial view of Bedford County, Pennsylvania, showing (from center to right): Wills, Evitts, and Tussey Mountains in December 2006

The province extends from southeastern New York in the north through northwestern New Jersey, westward into Pennsylvania through the Lehigh Valley, and southward into Maryland, West Virginia, Virginia, Kentucky, Tennessee, Georgia, and Alabama. They form a broad arc between the Blue Ridge Mountains and the Appalachian Plateau physiographic province, which includes the Allegheny and Cumberland plateaus. They are characterized by long, even ridges, with long, continuous valleys in between.

Significant ridges (from north to south)
NameState
Shawangunk RidgeNew York
Kittatinny MountainNew Jersey
Bald Eagle MountainPennsylvania
Blue MountainPennsylvania
South MountainPennsylvania
Jacks MountainPennsylvania
Moosic MountainsPennsylvania
Nittany MountainPennsylvania
Tuscarora MountainPennsylvania
Tussey MountainPennsylvania
Wills MountainPennsylvania and Maryland
Dans MountainMaryland
Sideling HillWest Virginia, Maryland, and Pennsylvania
Cacapon MountainWest Virginia
Knobly MountainWest Virginia
Mill Creek MountainWest Virginia
New Creek MountainWest Virginia
North Fork MountainWest Virginia
Patterson Creek MountainWest Virginia
Sleepy Creek MountainWest Virginia
South Branch MountainWest Virginia
Allegheny MountainVirginia and West Virginia
Great North MountainVirginia and West Virginia
North MountainVirginia and West Virginia
Shenandoah MountainVirginia and West Virginia
Massanutten MountainVirginia
Pine MountainKentucky, Virginia, and Tennessee
Clinch MountainTennessee and Virginia
Powell MountainTennessee and Virginia
Bays MountainTennessee
House MountainTennessee
Sharp's RidgeTennessee
Taylor Ridge (Georgia)Georgia
White Oak MountainTennessee and Georgia
Missionary RidgeTennessee and Georgia
Stringer's RidgeTennessee
Lookout MountainTennessee, Georgia, and Alabama
Red MountainAlabama


Ridges and valleys near Norton, Virginia in Wise County, Virginia
A map of the Cumberland Plateau and Ridge and Valley Appalachians on the border between Virginia and West Virginia
An aerial view Massanutten Mountain, including the south fork of the Shenandoah River (on left) and part of the Blue Ridge Mountains in Virginia

Geology

The Valley and Ridge Province was formed during the Alleghanian orogeny, a mountain-building event that occurred between 325 and 260 million years ago. [2] The rocks in the region were subjected to immense pressure and heat, causing them to deform and fold. The softer parts of these rock units (chiefly shale and limestone) were eroded to form the valleys and the harder parts of the folds (quartzites) formed the mountain tops and ridges. [3] The ridges represent the edges of the erosion-resistant strata, and the valleys portray the absence of the more erodible strata. Smaller streams have developed their valleys following the lines of the more easily eroded strata. [4] [5]


Blue Mountain in the Lehigh Valley region of Pennsylvania
Pennsylvania's ridge country seen from Clarks Knob in Franklin County, Pennsylvania

A few major rivers, including the Delaware River, the Susquehanna River, the New River, and the Potomac River, are older than the present mountains, having cut water gaps that are perpendicular to hard strata ridges. The evidence points to a wearing down of the entire region to a low level with little relief, so that major rivers were flowing in unconsolidated sediments unaffected by the underlying rock structure. The region was then uplifted slowly enough so that the rivers could maintain their course, cutting through the ridges as they developed.

Valleys in the region are either synclinal or anticlinal.

These mountains are at their development in central Pennsylvania, a phenomenon termed the Pennsylvania climax.

See also

References
  1. "Physiographic divisions of the conterminous U. S." water.usgs.gov. Retrieved September 6, 2023.
  2. Hatcher, R.D. "Tracking lower-to-mid-to-upper crustal deformation processes through time and space through three Paleozoic orogenies in the Southern Appalachians using dated metamorphic assemblages and faults". Geological Society of America Abstracts with Programs. Geological Society of America. Archived from the original on August 6, 2018. Retrieved January 23, 2012.
  3. Stanley, 421-2
  4. Stanley, 421-2
  5. "Valley and Ridge Province (U.S. National Park Service)". www.nps.gov. Retrieved September 6, 2023.

Further reading
  • WPA, Kentucky: A Guide to the Bluegrass State (1939); classic guide from the Federal Writers Project; covers main themes and describes every town and feature, with capsule histories online
  • Stanley, Steven M. Earth System History. New York: W.H. Freeman and Company, 1999. ISBN 0-7167-2882-6
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