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 even looked west from the Blue Ridge, down into the Shenandoah Valley, after climbing through different passes or low "gaps" in the ridge.
East of the Coastal Plain, the Continental Shelf can be treated as a specific 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 Rise. The Continental Rise is a steep underwater hillside, droping down from the Continental Shelf to the deep ocean bottom or the Abyssal Plain. The Continental Rise marks the edge of the continental tectonic plate. West of the Continental Rise is the lighter rock of Virginia, "floating" on the oceanic basalt. East of the Continental Rise is the heavy black basalt, the oceanic crust extending eastward to a range of underwater mountains in the middle of the Atlantic Ocean where basalt magma oozes up regularly via a crack in the crust.
The standard list of physiographic provinces for Virginia is usually land-centric, and includes:
Lederer was one of the first Europeans to make a transect across these provinces. From the Blue Ridge, he saw the Shenandoah Valley and the Allegheny Front (the edge of the Appalachian Plateau, on the west side of the Valley and Ridge province). There's a monument to him on Route 55 at Markham, east of Front Royal, on his supposed route through Manassas Gap. It's one of the many pieces of visual clutter that, if you slow down and look carefully out the window, can make the traffic headaches a little less burdensome.
How is the Blue Ridge (the location of Shenandoah National Park) different from Massanutten Mountain, the ridge just to the west that separates the North Fork of the Shenandoah River from the South Fork?
If you're a geologic province "lumper" rather than a "splitter," you can lump all the western Virginia bumps (including ther 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. Other geographers even lump the Blue Ridge together with the Appalachian Plateau and refer to the "Appalachians" in various discussions of colonial history and frontier settlement.
If you are a splitter, however, you can split 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 Virginia Natural Heritage Program also reflects a "splitter" perspective, because that program tries to identify areas of special significance within separate sections of the state.
Note that 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.
Physiographic region boundaries are based on geology, soil types, and topography. Contrast the geologic and physiographic maps on William and Mary's Geology of Virginia site, and you can see that the geology is defined in far greater detail than the physiographic region. The same is true for other categorization schemes, such as the Hydrogeomorphic Regions in the Chesapeake Bay Watershed
Physiographic regions are not based on cultural or biological features. The edges of cities or forests do not define the edges of physiographic provinces. Physiographic regions bear little relationship to political boundaries either. Instead, physiographic regions are defined by geology, soil types, and topography.
So - why would anyone bother to define areas with consistent landforms?
Looking at the areas with a similar geomorphology (shape of the land) helped scientists to identify the processes that created those physical features. That helps us identify likely mineral deposits (Virginia was once a major gold mining state...) and to anticipate environmental impacts from various changes in land use. Coors located a beer packaging plant in the Shenandoah Valley in large part because of the quantity and quality of groundwater near Elkton, which is a reflection of the limestone geology of that region.
In the Blue Ridge, ground water is less reliable - drilling a well does not guarantee finding water. There are cracks in the dense volcanic rock in the Blue Ridge, but there are places where the cracks are so tiny that little water is able to flow between them. In some areas, it's hard to pump enough water from underground to supply the 100 gallons or so that a family requires daily for drinking water, showers, laundry, flushing toilets, etc. Smart people drill their well before building their house, and some people still pay for "dowsers" to "witch" for water before spending $1,000-$4,000 on drilling a new well.
Our interpretation of the features that we can see on satellite images of the Earth also provides insights into the nature of other planets, such as Mars and Venus. That may sound marginal and esoteric - - but re-examining planetary geology (crater formation from meteor and comet impacts in particular) is helping scientists decipher the complex groundwater patterns near the mouth of the Chesapeake Bay. Newport News is struggling to find new supplies of fresh water, and those geomorphic patterns that shape the availability of drinking-quality groundwater could end up constraining economic growth on the Peninsula between the cities of Williamsburg and Hampton.
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.
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...
