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Drilling Reveals Washington, D.C. Sinking Fast Adapted from Information Provided by the University of Vermont New research based on extensive drilling in the coastal plain of Maryland confirms the land under the Chesapeake Bay is sinking rapidly, and projects Washington, D.C., could drop by six or more inches in the next century - adding to the problems of sea-level rise. This falling land will exacerbate the flooding that the nation’s capital faces from rising ocean waters accelerating the threat to the region’s monuments, roads, wildlife refuges, and military installations. For sixty years, tide gauges have shown the sea level in the Chesapeake is rising at twice the global average rate and faster than elsewhere on the east coast. Geologists have long hy- pothesized 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. A team of geologists from the University of Vermont at Maryland (UVM), the U.S. Geological Survey, and other institutions conducted the latest in- vestigation. Their study confirms Washington, D.C., is sinking, and provides a firm estimate of how quickly the drop is happening. Additionally, researchers’ detailed field data shows the land sinking around Washington is not primarily driven by human influence, such as groundwater withdrawals, but instead is a long-term geological process which will continue unabated for tens of thousands of years, independent from human land use or climate change. Washington's woes come from what geologists call “forebulge collapse.” During the last ice age, a mile-high North American ice sheet stretching as far south as Long Island, New York, piled so much weight on the earth that underlying mantle rock flowed slowly outward, away from the ice. In response, the land surface to the south, under the Chesapeake Bay region, was pushed upward. About 20,000 years ago, the ice sheet began melting away, allowing the forebulge to start sinking again. “It’s a bit like sitting on one side of a water bed filled with very thick honey,” explained Ben DeJong, lead author of the new study who conducted the research as a doctoral student at UVM's Rubenstein School of Environment and Natural Resources with support from the U.S. Geological Survey. “[When you sit], the other side goes up. But when you stand, the forebulge comes down again.” The new research provides the first high-resolu- tion data of how the forebulge has subsided - and will continue to. To design the study, researchers drilled 70 boreholes, many up to 100 feet deep, in and around the Blackwater National Wildlife Refuge, near Washington, on the Chesapeake’s eastern shore. Layers of sediment in deep cores were examined using a suite of techniques to calculate the age of the sand, other rocks, and organic matter in each layer. The team of scientists combined their collected data with high-resolution map data to create a detailed 3-D portrait of cur- rent and previous post-glacial geological periods in the Chesapeake, stretching back several million years. With this longer view, DeJong said geologists are confident they have a “bullet-proof” model showing the re- gion to be in an early period of land subsi- dence that will last for thousands of years. “Right now is the time to start making preparations,” said DeJong. “Six extra inches of water really matters in this part of the world.” Editor’s Note: In between our print issues, the WWDR Team prepares an electronic newsletter called E-News Flash . Based on read- ership, this was the most popular E-News Flash article of the month. Get in on the ac- tion and subscribe today at: www.worldwidedrillingresource.com 57 WorldWide Drilling Resource ® NOVEMBER 2015