![]() ![]() At times the process reversed and sea level rose briefly to drown the land again, with one such "transgression" occurring 35,000 years ago. It was not a steady, constant change every year the ice sheet grew and sea level dropped in distinctive steps. Sea level dropped and the Virginia coastline migrated to the east, exposing the sediments coating the former ocean bottom. At the start of the Wisconsin glacial stage, the Laurentide ice sheet grew, trapping water on land. The Continental Shelf and a portion of the current Coastal Plain were underwater 120,000 years ago, when sea levels were 20-25 feet higher. ![]() However, it is only recently that we have developed a clear understanding of how much the Virginia coast has changed over time. New spits of sand could appear after hurricanes, and dangerous new shoals could be created underwater when storms moved the sand. The sailors understood the shoreline was dynamic. Source: National Park Service, Shaded Relief Map of North America and Continental Shelfīy the time Europeans arrived in Virginia, the Atlantic Ocean coastline was marked by marshes and barrier islands on the Eastern Shore and wide sandy beaches south of the Chesapeake Bay. The bedrock of the continental shelf is relatively light continental crust, compared to the heavier basalt that forms the bottom of the oceans Sea level changes over the last 250 million years have exposed or submerged various percentages of the continental shelf. Source: National Oceanic and Atmospheric Administration, GLOBE: A Gallery of High Resolution ImagesĪ portion of the continental crust which forms the North American plate is submerged around the margins of the plate now. Virginia's eastern edge extends underwater across the Outer Continental Shelf Virginia and the Outer Continental Shelf Virginia and the Outer Continental Shelf (OCS) ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |