Sea Levels May Swamp Washington DC as Chesapeake Bay Sinks

Washington D.C. may be sinking-and fast. Scientists have found that the land under Chesapeake Bay is sinking rapidly and that Washington D.C. could drop by six or more inches in the next century, which could compound flooding issues.

For 60 years, tide gauges have shown that sea level in the Chesapeake is rising at twice the global average and faster than elsewhere on the East Coast. Geologists have already theorized for several decades that land in this area, pushed up by the weight of a prehistoric ice sheet to the north, has been settling back down since the ice melted.

In order to learn a bit more about this phenomenon, the researchers did extensive drilling in the coastal plain of Maryland. The researchers combined drilling data with high-resolution LiDAR and GPS map data to create a detailed 3D portrait of the current and previous post-glacial geological periods in the Chesapeake, stretching back several million years.

The main issue today comes from what is called "forebulge collapse." During the last ice age, a mile-high North American ice sheet piled so much weight on the Earth that the underlying mantle rock flowed slowly outward, away from the ice. In response, the land surface to the south, under the Chesapeake Bay region, bulged up. When the ice melted, though, the forebulge began to sink again.

"It's a bit like sitting on one side of a water bed filled with very thick honey," said Ben DeJong, one of the researchers, in a news release. "Then the other side goes up. But when you stand, the bulge comes down again."

The findings reveal that Washington is sinking. This, in particular, highlights the importance of taking steps now in order to avoid more flooding issues as sea levels rise.

The findings are published in the journal GSA Today.

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