On the rolling fields of the lower UCSC campus lies a geological mystery that still puzzles scientists to this day. Dubbed “Mima Meadow,” it is a terrain covered in small, round soil mounds that stand about three feet high and six feet across. They may not catch your attention if your on the ground, but once you see an aerial photo you can’t help but scratch your head and wonder how they formed.

New research shows that these mima mounds could well be the result of hundreds of years of gopher digging. A team of geologists from San Jose State designed a computer model to see if the large mounds could form based on simulating real gopher digging behavior. The model showed that in the process of digging over many generations, gophers can move enough soil to create mima mounds. Pebble by pebble, stone by stone, over hundreds of years, these small, furry animals can create giant mounds of earth with a repeating pattern resembling real mima mounds.

Still, some scientists reject the gopher theory, preferring erosion with no mammals involved. A group of geologists from Washington used lasers to measure mima mounds in the northwest US that are clustered around the margins of retreating glaciers. Their data suggest that mima mounds are the result of melt water runoff creating small pools and eroding the surrounding dirt. Eventually, as sediment is carried off over thousands of years, it creates mima mounds.

One reason for the elusive consensus on formation could be that mima mounds form differently in different landscapes. They are not exclusive to Santa Cruz, and are found in a multitude of places in Northwestern America, the central plains, and around the world. In the south central United States mima mounds are thought to form by yet a third theory: accumulation of wind-blown (aeolian) sediments around vegetation. Central California never had glaciers, so the glacial theory doesn’t hold here, and the geologic record does not show a lot of wind blown sediments. So the gopher theory, given the modeling results, seems to be plausible for Santa Cruz. Now we just have to see if we can find any surfing gophers!

Further Information

The Wikipedia entry on mima mounds is really good. You can read it Here.

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