Mysterious Mounds Attributed to New Source
Theory about soil, erosion may not be sexy, but it's convincing
By Elizabeth Armstrong Moore, Newser Staff
Posted Jun 24, 2014 6:55 AM CDT
Bryan Moss and Tracey Byrne from the Seattle area stop along the walking path in the Mima Mounds Natural Area Preserve Dec. 29, 2013, near Littlerock, Wash.   (AP Photo/The Olympian, Steve Bloom)

(Newser) – The mystery of the mounds lives on. A mere six months after researchers said computer modeling proved pocket gophers, over the course of several hundred years of scurrying and burrowing, formed the bizarre-patterned earthen "Mima mounds" in Washington state, a new team of researchers claims that plants are in fact the likely source. These mounds—which are up to 6.5 feet tall and 55 feet wide—are found on every continent but Antarctica, and in his study, Michael Cramer of the University of Cape Town sets out to debunk the gopher theory. He outlines a number of issues: Mima mounds appear in areas gophers don't inhabit; some of the mounds feature rocks bigger than the 2-inches-in-diameter stones pocket gophers are believed to be able to move.

And as for the previous claim that a series of gophers developed the mounds over hundreds of years, Cramer says there's no indication that abandoned mounds are repopulated over and over. His theory: The mounds have formed due to what is called vegetation spatial patterning. The idea, reports LiveScience, is that plants and their roots alter how wind or water may carry soil to these patches of vegetation, thus the mounds grow bigger over time as the plants continue to trap sediment. The vegetation could further stabilize the soil, thereby reducing erosion on the mounds while depleting the adjacent soil of water and nutrients, creating patterned dips. The researchers hope to test their theory on mounds in South Africa. Whatever the source, the News Tribune reports that Washington state is pushing to protect its mysterious mounds: Its Department of Fish and Wildlife recently requested $3 million from the state to do so. (Another mystery solved: the source of fairy circles?)

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Showing 3 of 8 comments
dillet
Oct 30, 2015 1:01 PM CDT
Whoever came up with the gopher theory knows nothing about the behavior of gophers and the structure of their tunnels and mounds. It just doesn't fit.
Ray Tort
Apr 13, 2015 12:30 AM CDT
I live near the Mima mounds. I’ve gone pheasant hunting in nearby fields when the ground and grass is frozen stiff. My theory is that the frozen grass is knocked down by wild life and paths are formed where the frozen grass is knocked down. When the grass thaws or it rains (There is a lot of rain here.), water forms tiny streams along these paths. When it refreezes, the grass remains knocked down. Over time the tiny streams (3 to 4 inches wide) remove sediment from these pathways and the wildlife prefers these pathways and avoids the randomly placed mounds. The mounds vary in height and diameter. The soil in the mounds is the same as that in the pathways – lots of sand, dirt and some tiny gravel. There are nearby prairies that do not have these mounds. A different fact to be consider is that in the not too distant past this whole area was a lake bed and there are artesian wells not too far away, but not in this area presently. Some mound in other countries appear on gently sloping hillsides. Browse “mima mounds.”
Ezekiel 25:17
Jun 25, 2014 9:08 PM CDT
Natives like to make mounds. We even have a placed called the Spiro mounds. I've seen mounds in the forested region of the state. Its in area first inhabited by the Caddos then later assigned to the Choctaws.