VA Geology Notes
- A Region of sedimentary strata, unconsolidated layers consisting of sand, mud, and gravel.
- Youngest rocks are located in this province.
- The coastal plains form a terraced (flat stair-stepped) landscape. Rivers are wide and meandering, with lots of marshes and wetlands.
- Extends from the Fall Line on the west boundary to
the Chesapeake Bay/Atlantic on the east.
- A mile-wide asteroid struck near the mouth of the Chesapeake Bay 35 million years ago.
- A region of gently rolling hills, good arable (fertile) farmland.
- Amazonite is an important gem from Amelia County
- Willis Mountain is the largest producer of Kyanite in the world. It is used in Sparkplugs and Space Shuttle Heat tiles.
- Largest province from the Fall Line on the east and then westward to the Blue Ridge Mountains.
- Dinosaur footprints are found in the province.
- Important rocks and minerals include slate (metamorphic rock from shale), and kyanite.
Blue Ridge Mountains
- A long narrow, northeast-southwest trending mountain chain.
- Granite is the oldest rock.
- The highest mountain in the state is Mount Rogers is elevation 5,719 ft in elevation.
Valley and Ridges
- Composed of folded and faulted sedimentary rocks.
- Most ridges are held up by harder erosion-resistant sandstone, and most valleys are underlain by softer less resistant shale, limestone, and dolostone.
- This is an example of Differentiated Weathering – harder rocks stay and softer erode away. Limestone easily dissolves in acidic groundwater.
- Karst features, such as caves and sinkholes are common throughout this province.
- The term “karst” is derived from a Slavic word that means barren, stony ground.
Karst is the name of a region in Slovenia near Italy that is known for its sinkholes and caves.
Ridge Valley Ridge
Harder Sandstone Softer Limestone Harder Sandstone
- Most of the rock layers are relatively flat-lying, with rugged erosion caused by streams.
- Overall a flat plateau but with steep, rugged, narrow twisting valleys caused by downcutting by streams.
- Consists of 320 to 280 million-year-old sandstone and shale with layers of coal beds.
- Coal is Virginia’s most important mineral resource. Wait… Coal – a mineral ???
Coal is not a mineral because it is organic, and minerals are inorganic.
Virginia Department of Mines, Minerals, and Energy lists coal in its mining
tax base which is why you might see coal identified under a mineral list.
It is NOT a mineral but it is taxed as a mined resource.