Travels in Cascadia: Burial Mounds of the Kings of the Rohirrim? The Mima Mounds of Washington

NOTE: If this post seems familiar, it should be. I posted it just a month ago. I'm re-posting (with minor changes) to place it in the proper order of the current blog series. 

One of the vivid images in my mind of the Lord of the Rings Trilogy was the resting place of the Kings of Rohan. They were buried in mounds, and the mounds were covered by the white flowers called Simbelmynë. I couldn't help think of the Kings of the Rohirrim when we arrived at the Mima Mounds Natural Area Preserve near Tumwater, Washington.

When European settlers reached the region, some of them thought that these unusual features were indeed Native American burial mounds. But when no further evidence could be found supporting the idea, they looked for other explanations. And didn't find many...

The things we don't know about our planet are, well, not known. But geologists are the first to say that the unknowns are legion. Many aspects of Earth are still a mystery. Lots of the mysteries lie hidden deep in the crust and mantle, or on the deepest parts of the ocean basins. But some mysteries are still right there in front of us, and mima mounds are one of them.

Mounded topography forms in a number of places across the central and western United States in a number of different geological environments. Although they share some similarities, it is possible that they originate from several different processes. Ideas range from the mundane to the exotic (and unlikely). Most of them occur when a fairly thin layer of soil covers a harder layer or substrate underneath. They tend to be just a few feet high, and occur in concentrations of 8-10 per acre.

The mima mounds of Washington formed at the edge of the massive ice sheet that covered most of Canada and parts of Washington as recently as 12,000 years, and so some hypotheses involve glacial meltwater, or subsurface glacial activity. Some suggest erosion of sediment from around concentrations of vegetation. More esoteric explanations involve disturbances from the vibration patterns of major earthquakes.

Occam's Razor states that among competing hypotheses, the ones that make the fewest assumptions are more likely to be correct (sometimes inaccurately described as the simplest answer is always the best). One of the more reasonable explanations for the mounds may be simply rodent activity. When pocket gophers dug into the shallow soils and encountered harder sediments, they tended to build up the mounds, and the process continued through thousands of generations. Maybe. And maybe it's aliens...

I managed to catch a photo of the mima mounds on approach to SeaTac a few years ago.

In any case, it's a fascinating place to visit. Several trails wind their way through the mounds, and there is an interpretive kiosk with a viewing platform. It is a beautiful prairie setting, with the tweeting of birds, the buzzing of insects...and an air of mystery.

I've been to the mounds in Washington twice, and the first time was in the dead of winter when no flowers were present. This time it was summer and it was a thrill to see the fields of flowers, bringing to mind the tombs of kings and the Simbelmynë.

If you want to visit the site, here are the directions from the park website:

From southbound or northbound Interstate 5, take Exit 95 and turn west on Highway 121 (Maytown Road SW) toward Littlerock. In Littlerock, continue west (forward past the school, past the intersection with Littlerock Road that curves south, and past the mini mart/gas station on the right) onto 128th Avenue. Travel about 0.8 mile where 128th Avenue ends at a 'T.' on top of the hill. Turn right onto Waddell Creek Road and travel about 1 mile. The entrance to Mima Mounds Natural Area Preserve will be on the left. A Washington State Discover Pass is required for parking at this site.

Postscript: Dustin commented when I posted the original last month, and these ideas have some merit...

Great features! My guess is that the mounds developed when glacial outflow preferentially eroded the fissures created by patterned-ground permafrost in a periglacial environment. This photo shows mounds forming from patterned ground in Alaska.

 https://en.wikipedia.org/wiki/File:Alaska_patterned_ground_1973.jpg 

In the case of the Mima mounds, if patterned ground was originally present with hard and frozen polygon centers, and margins/edges that were soft and thawed, then water flowing over the patterned ground would preferentially erode the fissures, while being less destructive to the polygon cores. Sustained flows would likely erode all evidence of patterned ground, but the Mima mounds were likely formed from ephemeral flow events associated with glacial melt near the ice sheet margins. This type of environment is suggested by the kettle lakes visible in the upper right of your airphoto, and the mounds being distributed amongst relict braided river patterns.

Burial Mounds of the Kings of the Rohirrim? Got a Better Idea? The Mima Mounds of Washington

One of the vivid images in my mind of the Lord of the Rings Trilogy was the resting place of the Kings of Rohan. They were buried in mounds, and the mounds were covered by the white flowers called Simbelmynë. I couldn't help think of the Kings of the Rohirrim when I arrived at the Mima Mounds Natural Area Preserve near Tumwater, Washington yesterday.

When European settlers reached the region, some of them thought that these unusual features were indeed Native American burial mounds. But when no further evidence could be found supporting the idea, they looked for other explanations. And didn't find many...

The things we don't know about our planet are, well, not known. But geologists are the first to say that the unknowns are legion. Many aspects of Earth are still a mystery. Lots of the mysteries lie hidden deep in the crust and mantle, or on the deepest parts of the ocean basins. But some mysteries are still right there in front of us, and mima mounds are one of them.

Mounded topography forms in a number of places across the central and western United States in a number of different geological environments. Although they share some similarities, it is possible that they originate from several different processes. Ideas range from the mundane to the exotic (and unlikely). Most of them occur when a fairly thin layer of soil covers a harder layer or substrate underneath. They tend to be just a few feet high, and occur in concentrations of 8-10 per acre.

The mima mounds of Washington formed at the edge of the massive ice sheet that covered most of Canada and parts of Washington as recently as 12,000 years, and so some hypotheses involve glacial meltwater, or subsurface glacial activity. Some suggest erosion of sediment from around concentrations of vegetation. More esoteric explanations involve disturbances from the vibration patterns of major earthquakes.

Occam's Razor states that among competing hypotheses, the ones that make the fewest assumptions are more likely to be correct (sometimes inaccurately described as the simplest answer is always the best). One of the more reasonable explanations for the mounds may be simply rodent activity. When pocket gophers dug into the shallow soils and encountered harder sediments, they tended to build up the mounds, and the process continued through thousands of generations. Maybe. And maybe it's aliens...

I managed to catch a photo of the mima mounds on approach to SeaTac a few years ago.

In any case, it's a fascinating place to visit. Several trails wind their way through the mounds, and there is an interpretive kiosk with a viewing platform. It is a beautiful prairie setting, with the tweeting of birds, the buzzing of insects...and an air of mystery.

I've been to the mounds in Washington twice, and the first time was in the dead of winter when no flowers were present. This time it was summer and it was a thrill to see the fields of flowers, bringing to mind the tombs of kings and the Simbelmynë.

If you want to visit the site, here are the directions from the park website:

From southbound or northbound Interstate 5, take Exit 95 and turn west on Highway 121 (Maytown Road SW) toward Littlerock. In Littlerock, continue west (forward past the school, past the intersection with Littlerock Road that curves south, and past the mini mart/gas station on the right) onto 128th Avenue. Travel about 0.8 mile where 128th Avenue ends at a 'T.' on top of the hill. Turn right onto Waddell Creek Road and travel about 1 mile. The entrance to Mima Mounds Natural Area Preserve will be on the left. A Washington State Discover Pass is required for parking at this site.

You Mean That Aliens Didn't Do It? New Research on Mima Mounds in the American West

Mima mounds south of Seattle, Washington

What's life without a little mystery? For years, geologists and geomorphologists have been curious about a landscape that shows up on prairie lands around the American West. It's a regular pattern of low hillocks called mima mounds. The hills are a few feet high and a few dozen yards across. They generally occur where there is a clay substrate that sometimes causes pools to collect between the mounds. These are called vernal pools, and for the few months that they hold water, they support a large variety of unique plants and animal species.

Mounds in the Yokohl Valley region in the Sierra foothills near Sequoia National Park.

The mima mounds are a mystery because their origin is not exactly clear. Early settlers thought they were burial mounds for Native Americans, but that is not supported at all by archaeological research. Some have suggested that they result from disruption of the soil by earthquake waves. The mima mounds I photographed from above (first picture) were in Washington near the margins of the vast continental glaciers, and some have speculated that they formed as a result of meltwater flooding in some fashion. Other less scientifically oriented observers suggest that aliens from space have something to do with their formations (landing pads, maybe?).

Mima mounds near Willms Road in the Sierra Nevada foothills near Knights Ferry on the Stanislaus River.

Of course, some people suggested that the origin might be a bit simpler (remembering Occam's Razor: among competing hypotheses, the hypothesis with the fewest assumptions should be selected). They suggested generations and centuries of activity by ground squirrels or gophers resulted in the formation of the mounds. In the prairie environment, the mounds would give the rodents a better view of approaching predators, and their burrows would stay drier, being above the impermeable clays.

I was pleased to run across some current research on the origin of these enigmatic mounds by Manny Gabet at San Jose State University, and the verdict is...gophers. Generation after generation of gophers, building their mounds in the same place over time. Gabet doesn't insist that this is the absolute explanation for all mounds, but the computer modeling provides strong support for the idea. The mounds would develop after around 500-700 years.

Snow patches outline mima mounds at Tehachapi Pass in southern California (photo by Mrs. Geotripper).

Sorry, alien lovers...maybe Roswell has some new evidence.