Plate Tectonics Topics

Plate Tectonics History of Virginia (Part 2)

750 to 560 Million Years Ago


• 750 million years ago, the Rodinia supercontinent that formed from continental collisions during the Grenville orogeny began to rift apart. This marks the beginning of a new Wilson Cycle.

750 m.y.a.
Reconstruction of the world 750 million years ago, showing the supercontinent of Rodinia. (Image courtesy of the United States Geological Survey)

• Rift basins formed, and volcanic rocks and continental sediments filled the basins.

• The best record of these events is found in the rocks of the Mount Rogers area in Grayson County.

Mt. Rogers volcanic rocks
Volcanic rocks that are 750 million years old are found in the Mount Rogers area. (Left photograph by Robert Whisonant; right photograph by Parvinder Sethi)

MapThese Grayson County rocks (above) are evidence of rifting. Lava flowed into the rift valley, forming the rhyolite in the left photograph.  An explosive volcanic event produced the tuff in the right photograph.