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Scientists scan mud for hurricane patterns

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To find out what makes a hurricane tick, you have to fly through it. To find out how often hurricanes strike land, you need to dig for them.

As more condos, office towers, and housing tracts spring up in cities along America's East and Gulf coasts, researchers are scanning mud they bring up from coastal marshes and ponds for clues about the history of major hurricanes.

The approach is relatively new, scientists say. With it, they hope to give residents, emergency planners, building and zoning boards, and insurers a better handle on the risk densely populated areas face from these storms. When combined with other emerging techniques, these "paleo-tempestologists" add, information they glean might help determine whether global warming could generate more- frequent or more-intense storms.

"The motivation is to extend the historical record" for major hurricanes, says Richard Murnane, who heads the Risk Prediction Initiative at the Bermuda Biological Station for Research.

The insurance industry is interested in the most intense storms, he says, but these are rare. Only three Category 5 storms - the most destructive - have hit the US in the past century. The latest was Hurricane Andrew, which struck Florida and Louisiana in 1992, killing 23 people and causing $26.5 billion in damage.

The potential of mud coring became apparent in 1993, when Kam-biu Liu and Miriam Fearn at Louisiana State University showed that paleo-hurricanes left their mark as sand layers in mud cores taken from the bottom of coastal lakes along the Gulf. But could the technique work for hurricanes along the East Coast?

"Initially, I was somewhat dubious," says Jeff Donnelly, a geologist at the Woods Hole Oceanographic Institution. He had spotted sand layers in mud cores he pulled from coastal marshes to study effects of changing sea levels on ancient ecosystems. The marshes sat behind barrier beaches, which can be overswept by tidal surges during storms. The surges drive sand into the marshes. But when powerful nor'easters clobber the East Coast they can generate surges of their own. Telling the two apart might be tough.


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