Reliable data on hurricane landfalls in the United States goes back about 150 years. In that time, few catastrophic hurricanes have come ashore, so meteorologists don't have enough statistical data to confidently estimate how frequently such powerful hurricanes strike.

That's why some hurricane researchers have become paleontologists, digging for signs of prehistoric storms. The clues come in the form of sand from the ocean floor or beach that was carried inland by the storm surges of past massive hurricanes. The displaced sand eventually settled to the bottom of coastal lakes and marshes, forming layers of sediment. Researchers have extracted cores from more than a dozen lakes and marshes along the Gulf Coast, and by dating sand layers in the cores, unlocked some secrets of hurricane history back about 4000 years.

Their data indicates that over time scales of centuries, we're presently in a relatively quiet period for catastrophic hurricanes along the Gulf Coast. Such storms struck four to five times more often 1000 to 3000 years ago than they do now. Their research suggests that a catastrophic hurricane strikes the Gulf Coast, on average, about once every 300 years. A similar study is also being conducted in New England with cores drawn from salt marshes in Rhode Island, Connecticut, and Massachusetts. This popular new branch of hurricane research has been dubbed "Paleotempestology."