A three-dimensional seismic image of the mantle beneath the Lau Basin in the South Pacific just published in Nature has an intriguing anomaly. The image showed the least magma where the scientists expected to find the most. After considerable debate, they concluded that magma with a high water content was flushed so rapidly that it wasn’t showing up in the images.
Douglas A. Wiens, PhD, professor of earth and planetary sciences in Arts & Sciences at Washington University in St. Louis, has been selected to receive the 2014 Robert L. and Bettie P. Cody Award in Ocean Sciences.
In March 2010, the ice sheets in Antarctica vibrated a bit more than usual as a surface wave from an 8.8-magnitude earthquake in Chile 3,000 kilometers away passed through the ice. Powerful earthquakes were known to trigger secondary quakes along faults in land; this was the first observation of triggered quakes in the ice. Washington University in St. Louis seismologist Doug Wiens says the finding is one of several discoveries made possible by POLENET, an array of seismic stations that reaches for the first time into the interior of Antarctica.
A temporary seismic array in Marie Byrd Land in West Antarctica recorded two bursts of activity in 2010 and 2011. Careful analysis of the events shows they originate from a subglacial volcano at the leading end of a volcanic mountain chain. The volcano is unlikely to erupt through the kilometer of ice that covers it but it will melt enough ice to change the way the ice in its vicinity flows.
The slow rebound of the bedrock as ice melts can be used to weigh the Antarctic ice sheet. Calibrating rebound will make it possible to measure how much mass the has lost since the ice sheets reached their maximum extent more than 20,000 years ago and how much it is currently losing. Two National Science Foundation grants will fund the installation of seismographs to calibrate crucial parts of the Antarctic ice-weighing machine.
Seismologists have just returned from a cruise in the Western Pacific to lay the instruments for a seismic survey that will follow the water chemically bound to or trapped in the down-diving Pacific Plate at the Mariana trench, the deep trench to which Avatar director James Cameron is poised to plunge.
In the weeks following the earthquake, two geologists at Washington University in St. Louis — Doug Wiens, PhD, professor and chair of earth and planetary sciences in Arts & Sciences, and Michael Wysession, PhD, associate professor of earth and planetary sciences — were frequently interviewed by journalists seeking to understand a catastrophe that seemed at times beyond understanding. What did the two scientists think about the quake? What was expected and what surprised them?