September 18, 2013
Examining all the data from the Virginia earthquake, Risheng Chu and several of his colleagues at the California Institute of Technology think they’ve identified an interesting feature beneath the seismically active region on the border between Missouri and Tennessee—a trail of hot rock left by a mantle hot spot.
Mantle hotspots are behind many island chains, like Hawaii, as well as continental volcanism, such as the Snake River Plain leading to Yellowstone. It’s not the hotspots that move. Rather, it’s the tectonic plate that moves over the hotspot, with the resulting linear scar recording past plate motion.
The New Madrid Seismic Zone is unusual in that it’s far from any plate boundary. While most earthquakes there are small, there have been some massive ones in the past, including several devastating quakes witnessed in 1811-1812. The earthquakes occur along faults created by a failed rift, where volcanic activity nearly split North America apart more than 500 million years ago.
There are other failed rifts without the same unruly earthquake behavior today, so what’s different here? One idea is that a mantle hotspot could have weakened this rift zone more recently (geologically speaking), creating the conditions for seismic activity.