Chesapeake Bay impact, artwork. 35 million years ago, a comet or asteroid impacted the eastern coastline of North America, forming a crater some 40 kilometres across that is now covered by the sediments and waters of Chesapeake Bay. It is thought that the object (bolide) that formed the crater was around 2 kilometres across. The bolide fractured the underlying rock to a depth of 8 kilometres, throwing millions of tons of water, rock and sediment into the atmosphere. The blast wave flattened and burnt forests (lower left) and massive tsunamis devastated the coastline. The crater walls, formed of soft sediments, collapsed within hours, and continuing settling under the weight of the new sediment disrupts the region's water supplies.