Tsunami of the Eocene
Every once in a while, there is a disturbance on the ocean floor. The aftereffects come in a series of waves called a Tsunami. A Tsunami can be made anyhow. It can be made by an earthquake, a plate boundary, a volcanic eruption, or even a meteorite that lands on the ocean floor. The gravitational pull of the moon can also be a cause, if it's too strong.
The Tsunami from the Eocene was a major event. It started when a meteorite from space landed in the Chesapeake Bay, right where the Chesapeake Bay Bridge-Tunnel is now. After that, disaster struck: A series of waves hit the coast of Virginia and Chesapeake. There weren't any humans alive then, but all prehistoric animals alive then died. There was a crater left under the bridge-tunnel, so we could assume that a Tsunami struck.
In conclusion, the Tsunami of the Eocene was a major event in prehistory.