Sand boils erupted along a 20-ft-long fissure in recent deposits of the Pajaro River to form a set of overlapping sand volcanoes. The aligned craters mark the location of the underlying fissure. Layers of sand in the conical deposit indicate multiple eruptions of sand, related to the 1989 Loma Prieta mainshock and its larger aftershocks. (From U.S. Geological Survey Open-File Report -90-547, photograph number XVI-3; photograph by J.C. Tinsley of the U.S. Geological Survey)

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