Over 18,000 people were killed by a magnitude 9.0 earthquake and subsequent tsunami that struck Northeastern Japan on March 11, 2011. The earthquake lasted six minutes, and had over 250 aftershocks.
Amateur video obtained by an American tourist visiting a park when the earthquake struck shows how dynamic the ground can be. The ground can be seen opening and closing, with some areas spurting water to the surface.
This is the result of a geological phenomenon known as liquefaction. When saturated soil experiences tremendous stress, like from tremors of an earthquake, the pressure of the water increases dramatically. This causes the soil particles to move more freely, essentially behaving more like a liquid than a solid.