The mysterious mounds of Mima

In spring, the soft mounds of the Mima prairie are covered with a delicate tapestry of grasses and flowering plants.

Last Monday was a holiday, so we decided to visit the Mima Mounds, one of the last remaining prairies in Washington state. This strictly protected natural park with its undulating, rounded mounds is something of a mystery. Six to eight feet high and thirty feet across, these soft hummocks form a strange, unreal landscape that no-one has been able to explain how it came into being.
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The Mima Mounds prairie covers today about 700 acres, but is greatly diminished from its earlier days.

There has been several theories of how the Mima Mounds were formed. The Upper Chehalis Tribe, the first peoples of the area, believed that they were left behind after a great flood subsided. "It rained and rained... and the whole world was flooded... there was nothing but prairie land beneath the water... at last the water fell, but the earth still remained in the form of waves." In the 1800s, European travelers and explorers were intrigued by the rounded, wavy prairie and their explanations for the mounds ranged from ancient burial sites to water-sculpted river beds.

The delicate stars of Camas, Camassia quamash. It was cultivated as an edible by the first nations of the Pacific Northwest.

  

Fine-leaved desert parsley, Lomatium utriculatum, is a favorite of butterflies.

Today, modern science has established that the Mima Mounds were formed after the ice-age glaciers receded about 16 500 years ago, but it is still a mystery exactly how. There are theories of intersecting earthquake waves that would have collected soil into tops and dales, about water patterns, and even that they were the work of pocket gophers excavating nest chambers (some industrious gophers, as the prairie reaches several miles in diameter).

Early blue violets, Viola adunca, provide food for caterpillars and butterflies. Many of them lay their eggs in the wilting leaves of the violets.

Prairie lupin, Lupinus lepidus, is another important food plant for caterpillars and butterflies.

Western buttercup, Ranunculus occidentalis, is native to the prairies of the West.

The Mima Mounds is home to several plant species, and in the spring time they form a delicate tapestry of flowers and grasses, filled with Camas, violets, chocolate lilies, buttercups and many other prairie species that are today well-known as garden plants around the world. For the first peoples, these prairies were an important source of food, and rights to tend parts of the prairie were inherited from generation to generation. Especially bulbs of the Camas, Camassia quamash, were an important source of carbohydrates, as they are sweet and tasty when slowly cooked. To keep the prairie from turning into forest, the first peoples burned their areas early or late in season, when the bulbs were dormant.

An old mound, overgrown with trees. If the prairie would not be burn with regular intervals, the forest would take over. The trees prefer to grow on the top of the mounds.

Today, some 700 acres of the Mima prairies are tended by the Nature Conservancy and the Department of Natural Resources, who practice controlled burning and weed management in the area. A small display about the history and vegetation has been installed for visitors, and platforms and pathways guide them through the area without damaging the fragile environment.

While wandering around the beautiful, slightly bizarre meadow, we couldn't help trying to find our own solution to the unsolved mystery. My daughters theory was that a flock of dinosaurs had laid their eggs and then been disturbed by something, leaving behind the soil-covered eggs. I thought theirs was at least as good as the gopher theory... until someone figures out what really happened.