Environment of Virginia - Physiogeographic Regions and Geology

Physiogeographic Regions and Geology

Geologically, Virginia is divided into five regions, while the EPA lists seven ecoregions with further precision. From east to west, the regions are as follows:

• The Tidewater is a coastal plain between the Atlantic coast and the fall line. It includes the Eastern Shore and major estuaries which enter the Chesapeake Bay. This region corresponds to the EPA's Middle Atlantic Coastal Plain (#63) and Southeastern Plains (#65) regions.

The Chesapeake Bay separates the contiguous portion of the Commonwealth from the two-county peninsula of Virginia's Eastern Shore. The bay was formed following a meteoroid impact crater during the Eocene. Many of Virginia's rivers flow into the Chesapeake Bay, including the Potomac, Rappahannock, James, and York, which create three peninsulas in the bay.

• The Piedmont is a series of sedimentary and igneous rock-based foothills east of the mountains which were formed in the Mesozoic. The region, known for its heavy clay soil, includes the Southwest Mountains. This region corresponds to the EPA's Piedmont (#45) and Northern Piedmont (#64) regions.

• The Blue Ridge Mountains are a physiographic province of the chain of Appalachian Mountains with the highest points in the state, the tallest being Mount Rogers at 5,729 feet (1,746 m). This corresponds to the EPA's Blue Ridge (#66) region.

• The Ridge and Valley region is west of the mountains, and includes the Great Appalachian Valley, which includes the Shenandoah Valley. This region corresponds to the EPA's Ridge and Valley (#67) region. The region is carbonate rock based (primarily limestone), and includes Massanutten Mountain. Because of the areas of carbonate rock and resulting karst formations, more than 4,000 caves exist in Virginia, with ten open for tourism. Likewise, another feature that resulted from limestone erosion in the valley region is the Natural Bridge.

• The Cumberland Plateau (also called the Appalachian Plateau) and the Cumberland Mountains are in the south-west corner of Virginia, below the Allegheny Plateau. In this region rivers flow northwest, with a dendritic drainage system, into the Ohio River basin. This region corresponds to the EPA's Central Appalachians (#69) region.

Coal mining takes place in the three mountainous regions at 40 distinct coal beds near Mesozoic basins. Besides coal, resources such as slate, kyanite, sand, and gravel are mined, with an annual value over $2 billion as of 2006.

Virginia has a low risk on earthquakes, especially in the northern part of the state. The Virginia seismic zone has not had a history of regular earthquake activity. Earthquakes are rarely above 4.5 in magnitude because Virginia is located centrally on the North American Plate, far from plate boundaries. Locations near tectonic plates suffer earthquakes frequently. The largest recorded earthquake, at an estimated 5.9 magnitude, was in 1897 near Blacksburg. The largest since then was in August 2011, when a 5.8 magnitude quake struck near Mineral, Virginia and was felt moderately to strongly throughout the state.