1. Virginia Geologic History and Regions

2. Take a look at cities you might have visited

3. There are 5 regions…. These are on your notes sheet provided to you

4. Coastal Plain Youngest sedimentary rocks in VA Low topographic relief:
Elevation on land: ft
Lands slopes east under the Atlantic Ocean & forms continental shelf; extends 200 miles offshore

5. Coastal Plain continued
Swamps: Great Dismal Swamp
Bays (Chesapeake) & estuaries
Extends westward to the “fall line”

6. The Fall Line…

7. Piedmont Rolling landscape
Slopes eastward from 1000ft to 300ft in the east
Weathering over long time has produced soils 150ft deep
Metamorphic, igneous, & sedimentary rocks present
Profile of the James River across the Fall Zone
Elevation
Distance from source

9. Blue Ridge Long & narrow region Elevations between 2300ft & 3200ft
Highest peak: 5719ft
Metamorphic & igneous

10. Valley and Ridge
Large valley: Shenandoah & other narrow, parallel valleys
Valleys in SW are 1000ft or higher than in NE valleys
Folded Appalachians
Sedimentary:limestone

11. Reported or known caves in Virginia

13. Appalachian Plateau SW part of state Flat high elevations
Sedimentary rocks (coal)
Drained by Tennessee River (to the W)

14. Observe the watersheds

15. On the next slides… Read each slide Copy what is underlined

16. Virginia’s Geologic History
Virginia is unique because it has:
Mountains
Hills and valleys
foothills
Sandy beaches…
All in 1 state!!

17. 1 bya (billion years ago)
VA was a little chain of volcanoes where the Blue Ridge Mountains are today
Everything else was underwater

18. 500 mya (million years ago)
Still underwater and a chain of volcanoes
Coastline located where valley and ridge are today
VA located S of the equator, had a tropical climate
Sediment was deposited over western VA, shells and coral were deposited, which explains the presence of
sedimentary rock in the
V & R (valley & ridge) and
A.P. (appalachian plateau) regions

19. 225 mya
Africa collided with North America, collision hard enough to wrinkle up the crust under the inland sea west of the Blue Ridge
“wrinkles” formed the Appalachian mountains

20. continued
The mountains were 15,000 to 20,000 ft, largest in the US (at that time)
Force of collision produced heat and pressure which changed some sedimentary rocks of limestone into marble
190 mya African plate started to pull away and the Atlantic opened, the pulling caused the land west of Richmond to stretch and crack, erosion caused these rift valleys to fill with mud and clay

21. 140 to 70 mya
Sediment from the eroding Appalachian mountains gets carried across the Piedmont by streams and rivers which washes into the Atlantic Ocean
Coastline is now located where Richmond is today
Over millions of years, sediments continued to build up which formed the Coastal Plain
… the sand on the beaches is actually rocks from the Appalachian Mountains

22. Ice Age-1.8 mya
Due to cold temps ice piled up in Canada and northern US
Ice sheets covered areas of North America, including parts of VA
Much of the water evaporated and the sea level was 450ft lower than today, VA coastline was 60 miles farther to the East
As glaciers melted sea level rose rapidly