About 35.5 million years ago an exploding meteor collided with Earth and formed a massive crater. Because rivers flow along the path of least resistance, the depression created by the crater caused river valleys to converge, setting the stage for the formation of the Chesapeake Bay. Millions of years later, the prehistoric Susquehanna River carved a 400-foot deep canyon as it flowed from the Appalachian Mountains toward the Atlantic Ocean. Rising sea levels at the end of the last ice age, about 10,000 years ago, flooded the Susquehanna River valley. Sediment has since filled much of the channel, forming the shallow Bay.
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