Mysterious Mima mounds may be due to gopher activity

BBC : Mima mounds refer to the dome-like sediment structures that cover vast expanses of prairie in the northwestern US. A single field may be covered by as many as a million of the mounds, some thousands of years old and ranging in size up to 50 m wide and 2 m high. Until now their origin has been a mystery. Various explanations have been proposed, including that they were Native American burial sites or remnants of earthquakes or glaciers. According to a recent study conducted by Manny Gabet of San Jose State University in California and colleagues, however, they were probably formed by pocket gophers. The researchers used computer modeling to show how the small mammals can shift tiny amounts of dirt over hundreds of years to create the large, extensive features. Because Mima mounds have been seen on every continent but Antarctica and gophers are native only to North America, Gabet suggests that other small, burrowing mammals may be responsible in other parts of the world.