The Mysterious Mima Mounds

Written By: Unexplained Earth
Posted: 1/8/2004

Throughout western America from Washington to Texas, strange mounds found dotting the landscape have perplexed both scientists and interested onlookers for over a century. No one is sure how the mounds were formed, but the theories surrounding them seem endless. About an hour south of Seattle lies one of the most accessible examples of these strange landscape features that have been dubbed the Mima Mounds.

On our trip from Los Angeles to Vancouver up the Pacific coast, my friend Eric and I had already visited one mound site several days earlier. Frankly, we were unimpressed with this previous site located in central California, but we decided to stop and have a look at the Mima Mounds Natural Area Preserve and I’m glad we did.

As we pulled into the parking lot, I could immediately see that this was a much more interesting place than the previous mound site we had seen. Encompassing well over 400 acres, the preserve is set up to really show off the mounds and educate the public about the many theories that surround them. Stretched out before us across the prairie were thousands of large, well formed mounds of earth of various sizes. Most were five to eight feet tall and perhaps ten to twenty feet in diameter.

The Mima Mounds have fascinated visitors for so long because of their unexplained origins. The first impression one usually gets when seeing them is that they are man made. In fact, they closely resemble ancient burial mounds found all along the east cost. However, no similar burial practices are known to exist among the native inhabitants along the Pacific coast. Furthermore, numerous excavations on the Mima Mounds and similar sites have not yielded any artifacts or skeletal remains. In the language of the native Chinook, “mima” does refer to death or burial. However, the Chinook have no known legends regarding the origins of the mounds.

So if they aren’t burial mounds, what are they? The theories that have been proposed run the gamut, but so far, no single theory seems to completely account for the mounds.

A number of geological theories have been proposed over the last 100 years. In 1940, R. C. Newcomb proposed that the mounds were created during the last ice age when the frozen prairie became fractured and formed a network of mound sized chunks that then gradually thawed. Repeated freezing and thawing would have divided the cracked segments further. This theory did not address the mounds shape however.

In 1953, Arthur M. Ritchie expanded upon this idea by adding that the mounds conical shapes could be accounted for by erosion of the partially thawed blocks. As the blocks melted, floodwaters would run between them further expanding their shapes. Ultimately, the blocks of frozen ground would melt like an ice cube so that the more exposed corners melted away first until the mounds eventually evolved into their present rounded shapes.

Geologists further maintained that the mounds were preserved and prevented from being washed away by both slow erosion and a bog that formed over the prairie soon after the mounds were created. In 1976, geologist Michael McFaul found evidence for just such a bog when he excavated several of the mounds.

An alternative geological theory that has gained some popularity in recent years was proposed by Andrew Berg in 1989. Berg linked the formation of the mounds to seismic activity. As evidence, he covered a sheet of plywood with soil. By vibrating the plywood he was able to reproduce a bumpy landscape eerily similar to the Mima Mounds.

Another popular theory proposed in 1941 by Walter Dalquest and Victor B. Scheffer, holds that the mounds are the work of industrious pocket gophers. About 10,000 years ago, gophers migrated to the Mima prairie. Unable to burrow into the hard gravel, the gophers may instead have arranged the topsoil into mound shaped nests that proceeded to grow in size over many generations.

Dalquest and Scheffer offered a number of observations in support of their claim:

Gophers are anti-social creatures and the spacing of the mounds is similar to the distance between underground gopher homes.

Ten gophers on a single acre of land can move up to five tons of earth within one year.

Found within the mounds are small cavities called “mound roots” that may be the abandoned gopher tunnels that have since filled with silt.

The Mima mounds are composed of rocks that are the correct size for a gopher to handle while the rocks found beneath the mounds are too heavy for them to carry.

This last point is in some dispute though. In Weird America, Jim Brandon states that rocks between two and 20 inches thick have been found inside the mounds, well above the level of the ground. There are no gophers currently found on the Mima prairie, although gophers are found at other similar mound sites only miles away.

Another point Brandon brings up that may overturn many of the theories presented here, is that the mounds may still be growing taller. He quotes one local farmer as saying, “Sure they’re growing. When I was a kid they were level with the top of the chicken coop. Now they’re several inches taller.”

The most fanciful explanation for the creation of the mounds is that Paul Bunyan, after hearing of the Great Wall of China, wanted to erect a similar wall here in America. He then hired a team of Irish workers to help him build the wall, but he kept driving them to make it larger. Eventually the workers became frustrated and abandoned their wheelbarrows where they stood. The wooden wheelbarrows eventually rotted away until all that remained were mounds of earth.

In Lost Cities of North and Central America, David Hatcher Childress mentions the similarity between the Mima Mounds and mounds found on the island of Bahrain in the Persian Gulf that are acknowledged to be the work of ancient man. In Guatemala, mounds can be found spread throughout the Petén jungles that are believed the be the remnants of platforms or small pyramids used to raise homes off the jungle floor. Childress postulates that the Mima Mounds might actually be the remnants of a lost civilization over 10,000 years old.

As I pondered the mounds’ possible origins, we followed the path from the car to a large kiosk that gave detailed diagrams and information on the theories surrounding the mounds and their composition. Stairs in the kiosk led us up to a viewing platform that afforded us a wonderful panorama of the Mima prairie.

From the information center, a paved path winds through the mounds leading to another viewing platform and an additional trail that can be followed for some distance through the mounds. The weather was beginning to look ominous again and a light drizzle fell, so we decided to stay on the main path and only walk the shorter of the two trails through the mounds.

After walking through the mounds, I again thought through the possible theories surrounding their origins. At one time there were as many as one million mounds to be found on the Mima prairie and in some places they still number over 10,000 per square mile. The sheer number of mounds plus their distribution from Washington to Texas would seem to argue against a manmade origin. In walking through them, I noticed they do not seem to be the right size and shape to support dwellings and it is hard to imagine them lasting 10,000 years without being eroded further on the exposed prairie.

I personally favor either the geological erosion theory or the seismic theory. The seismic theory would seem to be the only one that would explain the mounds continuing to grow larger over time.

As we approached the car, we could clearly see that the mounds continued into the forest and many of them had large trees growing out of them. Obviously the mounds had been here for a long time, but exactly how long, no one can say for sure. Despite the varied theories surrounding the origin of the mounds, we still don’t really know how they were created. Perhaps we’ll never know.

To reach the Mima Mounds Natural Area Preserve from Seattle, travel south on Interstate 5 past Tumwater and turn off at exit 95. Take the road west towards Littlerock, then follow 128th Avenue until it reaches Waddel Creek Road. Turn right and follow the road north for about a mile until you come to a small brown sign and a gate on the left marking the entrance to the preserve. A paved road winds through the trees to the parking area.

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