Eastern Virginia's bedrock is buried under glacial-till dirt.
The bedrock structures underlying eastern Virginia influenced the formation of the region's topography and land forms. The Atlantic coastal plain region of eastern Virginia is one of the East Coast's flattest geological provinces. It was formed early in the Mesozoic Era as volcanic rift zones of molten magma, or melted rock, broke up the Pangea supercontinent.
Mesozoic Erosion
Western Virginia's Blue Ridge Mountains and the Piedmont physiographic province was home to Himalayan-sized mountains. Millions of years of weathering and erosion during the Mesozoic and Cenozoic Eras created large amounts fine sediment composed of tiny rock particles. The sediment was blown by the wind and carried by running water to be deposited on the lower eastern Piedmont and Coastal Plain geological regions of Virginia. The fine-grained sediment accumulated in low spots, including ancient river beds, large lakes and oceans.
Coastal Sedimentary Bedrock
Coastal plain sediments were laid down in distinctive layers. As the sediment beds built up, water was squeezed out and the layers cemented together, bonding into solid rock. The coastal plain sedimentary bedrock structures are wedge-shaped, increasing in thickness toward the east and thinning out as the rock aproaches the Piedmont. The bedrock structure determined the gentle slope of the Atlantic coastal plain as it continued into the ocean to form the continental shelf.
Piedmont Bedrock
The bedrock under the Piedmont region is composed of igneous and metamorphic rocks formed during the Late Proterozoic and Paleozoic Eras. The ancient bedrock is covered with a layer of Mesozoic-age sedimentary rock marked by intrusions of hard-rock granite from the Late Paleozoic Era. The granite sometimes contains gold. Bedrock outcrops in the Piedmont are heavily weathered and exposed along river banks and stream bottoms. The Piedmont bedrock structure produced a largely flat and featureless terrain.
Triassic Basins
The eastern parts of Virginia contain sporadic bedrock fault formations called Triassic Basins, though the basins' lower levels contain older lower Jurassic-age rocks. The basins were formed by the separation of Africa from North America. The basins filled with layers of eroded rock compressed into sedimentary stone. The basins often contain red rocks, coal deposits, fish fossils and fossilized dinosaur tracks from ancient tropical lakes and mudflats. Isolated intrusions of igneous bedrock and lava flows cut through the sedimentary bedrock of the basins.
Tags: Atlantic coastal, Atlantic coastal plain, bedrock structure, bedrock structures, coastal plain, eastern Virginia
