Array of six hydrophones An array of six hydrophones (yellow stars) recorded 7,785 seismic events (red dots) between 1999 and 2002, mostly along the Mid-Atlantic Ridge and the Puerto Rico and Caribbean Trenches. A close-up of one portion of the ridge reveals that land-based seismographs recorded far fewer seafloor seismic events (white triangles) over a much longer period (26 years). (Courtesy Deb Smith)
