Blue Ridge and Shenandoah Valley
The collisions of continents and the erosion by rivers have left impacts obvious to even the untrained eye. In 1670, the early explorer John Lederer understood that Virginia was not a homogenous place. He recognized that every part of the colony did not look just the same as every other part, and the landscape could be classified by the topography or landforms:
John Lederer recognized the distinct character of what today we call the Coastal Plain (between the Atlantic Ocean and the "falls of the great Rivers," where Washington, Fredericksburg, and Richmond developed), the Piedmont (the "Highlands" stretching westward from modern Interstate 95 to the base of the Blue Ridge Mountains), and the Blue Ridge (the "great ridge of Mountains" or Apalakin, from which we may get the name Appalachia). Lederer probably looked west from the Blue Ridge, and may have gone down into the Shenandoah Valley after climbing through different passes or low "gaps" in the ridge.
Virginia is divided into various physiographic regions defined primarily by a combination of geology (the rocks underneath the soil) and topography (hills, valleys, and flat spots). Political boundaries are well-marked in Virginia, with signs on roads identifying when you cross a boundary between counties/cities. However, it's less obvious where to draw the line between physiographic regions. Not everyone might draw the exact same physiographic boundaries for locations in Virginia area. Typically, geologic boundaries are defined more precisely than physiographic region boundaries.
A map of the different ages of the rocks in the state provides a clue, but the boundaries of geologic provinces based on bedrock do not match up exactly with the edges of physiographic provinces. The geologic and physiographic maps on William and Mary's Geology of Virginia site, shows the bedrock of the Blue Ridge east of the steep slopes of the mountains. The bedrock that could define the eastern edge of the Blue Ridge geologic provice extends beyond Charlottesville, but many people would describe that ciy as being located in the Piedmont physiographic province (rather than the Blue Ridge).
The standard list of physiographic provinces for Virginia includes:
This list omits the area east of the Coastal Plain, under the Atlantic Ocean. There, the Continental Shelf can be treated as an additional physiographic province, extending from the shoreline into the Atlantic Ocean. The shelf extends eastward to a depth of 100-200 meters, and then the edge of the continent drops down relatively steeply to the deep bottom of the Atlantic Ocean. If you want to be very specific about the underwater physiographic provinces, then you can separate the flat continental shelf from deep ocean bottom, and define a zone in-between the two.
The flat Continental Shelf extends from the edge of the shoreline (where surfers ride the waves) eastward to the Continental Slope (or Rise). The Continental Slope is a steep underwater hillside, droping down from the Continental Shelf to the deep ocean bottom known as the Abyssal Plain. The Continental Slope marks the edge of the continental tectonic plate. West of the Continental Slope is the lighter silica-rick bedrock of Virginia, "floating" on the silica-poor oceanic basalt. East of the Continental Slope - out into the middle of the ocean - is the heavy black basalt. The oceanic crust extends eastward to the Mid-Atlantic Ridge, a range of underwater mountains in the middle of the Atlantic Ocean where basalt magma oozes up regularly via a crack in the crust.
John Lederer was one of the first Europeans to leave a record of a transect across the physiographic provinces on the land. There may have been earlier explorers who created no reports; someone with less culture but more moxie may have beaten Lederer to the western edge of the colony, but any such explorer left no records - so Lederer gets the credit.
There's a monument to John Lederer on Route 55 at Markham, east of Front Royal. It's on his supposed route through Manassas Gap. There's a fair chance that he once stood at that spot. The monument is one of the many pieces of visual clutter that, if you slow down and look carefully out the window, can make traffic headaches a little less burdensome.
From the top of the Blue Ridge, Lederer saw the Shenandoah Valley and the Allegheny Front. The "front" is the edge of the Appalachian Plateau, on the west side of the Valley and Ridge province. On the Appalachian Plateau, the layers of rock are no longer folded extensively, in contrast to the extensive deformation of rock in the Valley and Ridge province.
Note that the Blue Ridge (the location of Shenandoah National Park) can be classified in a different physiographic province than Massanutten Mountain, the ridge just to the west. The bedrock of the Blue Ridge is dramatically different from the bedrock of Massanutten Mountain, which is treated as one of the ridges in the Valley and Ridge province.
Massanutten separates the North Fork of the Shenandoah River from the South Fork. If you stood on the Skyline Drive and looked west from Swift Run Gap, you'd see the southern edge of Massanutten - and then a wider valley south of Massanutten Mountain.
If you're a physiographic province "lumper" rather than a "splitter," you can lump all the western Virginia bumps (including the Blue Ridge) together into one or two provinces, eliminating the Blue Ridge as a unique province. Lumpers treat the Blue Ridge as just one of the many ridges in an expanded interpretation of the Valley and Ridge province. Cultural geographers may even lump the Blue Ridge together with the Appalachian Plateau and refer to the "Appalachians" in various discussions of colonial history and frontier settlement. (John Lederer, who knew little about the mountains west of the Shenandoah Valley, was a lumper.)
If you are a splitter, you can separate not only the Blue Ridge from the Valley and Ridge, but also the "Great Valley" or Shenandoah Valley into a sub-unit of the Valley and Ridge physiographic province:
The edges of physiographic regions are not based on cultural or biological features, such as political/urban boundaries or forested/developed lands. So - why would anyone bother to define areas with consistent landforms?
The Virginia Natural Heritage Program identifies areas of special significance within separate sections of the state. Physiographic provinces are particularly useful for identifying natural communities and where rare/endangered species should be protected. Type in "physiographic region" or "physiographic province" in a search engine and note how many studies of birds, plants, and preservation of natural areas organize information and make recommendations based on physiographic province boundaries.
The names of physiographic regions may not match up exactly - but the boundaries are consistent with other classification systems. The "Cumberland Plateau" of the Virginia Natural Heritage Program is equivalent to the "Appalachian Plateau" defined by others. Also, you'll see different spellings in different places. If you want to know if Allegheny or Alleghany is the correct spelling, ask a local resident... and go with their advice.
Note that the edges of physiographic provinces are not mapped at a detailed scale, such as the 1:24,000 quadrangle maps used by hikers or the 1:400 scale plats used by county assessors for property tax purposes. Physiographic provinces define regional boundaries intended for general orientation, so specific sites (such as those being examined in environmental impact statements) can be put into context. Locations of property boundaries, roads, archeological sites, and wetlands are mapped far with far more detail that the edges of the physiographic regions.
| For example, one study at the Virginia Institute of Marine Sciences drew a map showing the provinces based on county boundaries. Obviously the straight lines defined by surveyors don't have a direct relationship with Virginia's natural features, but organizing information by county and physiographic province can still be useful.
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 simplified physiographic boundaries Source: "A Review of Nontidal Wetland Projects and Impacts in Virginia, 1991 - 1993 |
The boundaries of the current physiographic provinces are not permanent. During the last Ice Age, sea levels were 350-400 feet lower and much of today's Outer Continental Shelf was exposed. Some of Virginia's earliest archeological sites are probably buried under salt water and sediments deposited in the last 10,000 years as the sea levels have risen. During warmer epochs when glaciers melted and sea level rose even higher, the edge of the Atlantic Ocean would have been roughly where I-95 is located today. Go back further in geologic time, such as 200 million years ago when Pangaea was splitting up, and the physiographic provinces of Virginia would have been dramatically different...
