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Southeast U.S.

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Southeast USA

Evidence of tilting of the U.S. coast

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South Africa

Accurate sea level markers

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Roe Plains, Australia

The team’s first expedition

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Virginia

Researchers take advantage of a celestial collision

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New Zealand

Uplift exposes a repository of Pliocene sediments

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Enewetak

Researchers study crater of hydrogen bomb test

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southeast-us

This low rise doesn’t look like much, but if traced carefully, it continues for several hundred miles. It’s the greatly eroded remains of a three-million-year-old shoreline.

Photo courtesy Pliomax

Researchers have long been aware of a long ridge, known as a scarp, roughly paralleling the coastline of North Carolina, South Carolina, Georgia and Florida, about 150 kilometers (90 miles) inland. It is known as the Orangeburg Scarp in the Carolinas and the Trail Ridge in Georgia and northern Florida. The scarp is the eroded remnant of what was once an ancient seashore. It was formed by wave action over a long period of high sea level during the Pliocene. In October 2012 and February 2013, the Pliomax team traveled most of the length of the scarp, making accurate measurements of its elevation. They discovered that the elevation of the scarp is not constant over its length, as would be expected from a feature formed at sea level. The height of the scarp rises from about 15 meters (49 feet) in Florida to more than 75 meters (246 feet) in North Carolina. This tilting of the ancient shoreline suggests that the U.S. coast has undergone substantial tectonic movement since the scarp was created during the Pliocene. The Pliomax team will factor in this finding when calculating Pliocene sea level.