Virginia Geology and Soil Sciences – Master Naturalist Training

The following is what I learned about Virginia’s geology and soil sciences during my first session of Virginia Master Naturalist training.

Virginia Geology

Plate tectonics drive a cycle for the creation and transformation of igneous, sedimentary, and metamorphic rocks. Plate tectonics includes divergent plates with fresh material in the middle, transform boundaries where two plates slip past each other (earthquakes), and convergent plates where one plate subducts underneath the other creating volcanoes (e.g., pacific northwest US).

Igneous rock are lava or magma cooled above or the the below the earth’s surface. Intrusive igneous rocks cool slowly below the surface and have large crystals. Extrusive igneous rocks cool quickly above the surface and have small crystals. Chemical (i.e., dissolving) and physical (i.e., wind, ice) weathering on igneous rocks creates small particles that are transported (e.g., water, wind) and deposited. Weight pressure from layers of deposits create sedimentary rock. Sedimentary and igneous rocks that are forced downwards experience increases in heat and pressure that transform them into metamorphic rocks.

Virginia has a low risk of earthquakes because it is far away from convergent plates and relatively far away from the New Madrid Fault Line in Missouri. Eastern and western Virginia are comprised primarily of sedimentary rocks whereas the central regions of the state include metamorphic and igneous rocks. Virginia’s caves are the result of chemically weathered limestone. An interesting note is that I-95 was built to connect port towns that ships used to be able to reach via waterways. Finally, North America is moving an inch/year towards Japan (human nails and hair grow an inch/year).

A high level geological history of Virginia includes the original super-continent Rodinia breaking apart putting Virginia on the continent’s edge where thick layers of basalt and charnockite formed. In addition, remains of tiny sea creatures were deposited and have created limestone in the state that is 25,000 feet thick. Further, the Appalachian mountains were formed when the continent of Africa rammed into North America.

Soil Sciences

Soils are the interface between the earth and the sun’s energy. They are a complex ecosystem comprised of living and non-living things. In addition, they grow plants, regulate water, and recycle raw materials.

Virginia’s soils are typically red which means they are weathered and well drained (i.e., rich in oxygen). Grey/blue soils are saturated with water and poorly drained. Blacks soils (e.g., coal) are comprised of organic matter. Western Virginia has a moist climate and soils classified as inceptisols. Eastern Virginia has old temperate soils classified as ultisols.

Particle size affects soil properties. Sandy soils comprised of small particles do not hold water and are not compacted. Clay soils comprised of larger particles hold water and are compacted.


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