Paleontology and geology
During the Tertiary, the Coastal Plain of Virginia experienced alternating intervals of erosion (as sea level fell) and deposition (as sea level rose). The Chesapeake Bay impact structure was formed 35.5 million years ago when an extraterrestrial object – perhaps a large meteorite – slammed into what is now Chesapeake Bay. The Yorktown Formation, exposed along the York River, is one of many sedimentary units that is rich in marine fossils such as whale bones, snails, and clams. This map indicates the presence of Tertiary rocks across the central-eastern part of the state.