Seismometers record underwater eruption
A team of US geophysicists will easily get over the loss of two-thirds of their ocean floor seismometers: the instruments failed because an underwater volcano had erupted in their immediate vicinity. Although most of the instruments anchored at a depth of 2,500 meters were trapped by the outflowing lava, the remaining four provided for the first time ever a detailed look at what is happening during the formation of new seafloor. By sheer coincidence, the scientists had picked just the right time and place for their observations of seismic activity.
The team led by Maya Tolstoy from the Lamont-Doherty Earth Observatory at Columbia University in New York laid out the seismometers in 2003 around 600 kilometers off the Mexican coast along the East Pacific Ridge. This area, where two tectonic plates - the Pacific and Cocos plates - are moving away from each other, has long been known for its volcanic activity. As an initial evaluation of the recorded data showed, a short time after the instruments were sunk, a series of micro-earthquakes began, which continued to increase in strength and frequency until the eruption. After the eruption in January this year, the ground calmed down quickly.
Three months later, researchers were surprised at how few gauges responded to the surfacing signal. Cloudy and warm water near the bottom indicated that the area may have been the scene of a recent volcanic eruption. A second research ship that was specially summoned confirmed this suspicion: Instead of sediments and a rich fauna, a research submarine found fresh, glassy solidified lava on the sea floor, which was covered with a white layer of bacteria.
Until now, recordings from underwater microphones and land-based seismometers have been relied upon to reconstruct the eruption of a deep-sea volcano, the researchers said. In areas like the East Pacific Rise, however, the seaquakes that accompany the eruptions are considered too weak for such distant measuring devices.
