Sand volcano following earthquake. This sand boil or sand volcano (2 metres in length) erupted in soil by Interstate Highway 80 west of the Bay Bridge toll plaza when ground shaking transformed loose water-saturated deposit of subsurface sand into a sand-water slurry (liquefaction) in the 17 October 1989, Loma Prieta earthquake, California, USA. This behaviour of granular materials is being studied in a field of science called Mechanics of Granular Materials (MGM). Experiments aboard the Space Shuttle use the microgravity of space to simulate this behaviour under conditions that cannot be achieved in laboratory tests on Earth. Applications include earthquake engineering and granular flow technologies. Photographed on 21 October 1989.