US capital is sinking

Science : Even if water levels don’t rise as much as expected over the coming century, Washington, DC, will still suffer additional flooding as the land it’s built on sinks 16 cm over the next 100 years. It may eventually be under water as the land drops up to 40 m over the next 80 000 years. The cause is the last ice age, and in particular the Laurentide Ice Sheet, which covered much of northern North America. The sheet’s weight pressed down the underlying earth, which pushed up land farther south, such as the Washington, DC, area. When the ice sheets retreated, the land started sinking back down. The details, published in GSA Today , are from sediment core samples that have undergone a new technique using electrons trapped in quartz crystals for dating sediment. Electrons are trapped at a predictable rate when the sediment is underground. When they are exposed, the rate changes. Not everyone agrees with the interpretation, but the findings, if backed up with other evidence, will significantly affect our understanding of the geology of the region.