Sand boil
From Wikipedia, the free encyclopedia
Sand Boils occur when water under pressure wells up through a bed of sand. It looks like it is "boiling" up from the bed of sand hence the name. It also appears from a web search that this phenomena can be either man-made or natural.
An example of this is during the 1989 earthquake in San Francisco, when Sand Boils brought up debris from the 1906 earthquake.