Wednesday, December 16, 7:00 pm, in the Qrius theater, National Museum of Natural History, Constitutional Ave. Washington, DC
The Chesapeake Bay impact crater and its impacts.
David Powars — Research Geologist, Geology and Paleoclimate Science Center, United States Geological Survey, Reston, VA
About 35 million years ago, during late Eocene time, a 2-mile-wide asteroid or comet smashed into Earth in what is now the lower Chesapeake Bay in Virginia. The oceanic impact vaporized, melted, fractured, and (or) displaced the target rocks and sediments and sent billions of tons of water, sediments, and rocks into the air. Glassy particles of solidified melt rock rained down as far away as Texas and the Caribbean. Models suggest that even up to 50 miles away the velocity of the intensely hot air blast was greater than 1,500 miles per hour, and ground shaking was equivalent to an earthquake greater than magnitude 8.0 on the Richter scale. Large tsunamis affected most of the North Atlantic basin. The Chesapeake Bay impact structure is among the 20 largest known impact structures on Earth. Continued subsidence and sediment compaction within the structure has maintained a topographic low that has caused geologically recent and modern rivers to drain toward it, thereby controlling the location of the Chesapeake Bay to some extent. These observations point to the fact that this 35-million-year-old impact structure is still affecting us today.
Non-Smithsonian visitors will be escorted to the Q?rius theater at 6:45 and 6:55 p.m. Society members will host the speaker for dinner at the Elephant & Castle (1201 Pennsylvania Ave.) prior to the meeting. Members may meet at the restaurant or inside the Constitutional Ave. entrance of the NMNH at 5:00 and walk to the restaurant as a group.