Drive by the Edgewood Rest Stop along Interstate 5 and you will notice rounded shapes in the surrounding prairie land. I often slow down to look them over. During some times of the year their appearance is more obvious, probably due to the seasonal difference in colors of grasses and weeds on the mounds compared to their lower margins. What might have caused these odd mounds?
Although I like to think that Siskiyou County is special, similar mounds exist in many other areas. They are found throughout the Pacific Northwest and all the way south to Baja California. They can be seen in our Great Plains, the mid-West and other parts of the world. They were first noticed and studied in western Washington, near a place called Mima Prairie, resulting in the name they are now known as—Mima Mounds.
Early on the possibility of a Native American origin for the mounds was studied but excavations failed to uncover artifacts or remains of prehistoric structures. Another idea was that gophers or other burrowing animals might have been responsible, but that notion had no evidence to support it. Some people suggested that they even might have been formed by landing UFOs!
In Shasta Valley and the Mima Prairie they on found on flat ground that has been covered by glacial outwash. This means that both areas were near glaciers, thousands of years ago. When the glaciers were melting, large amounts of stones, mud, sand and other debris were deposited over the terrain. The outwash covering the Edgewood Rest Stop area might have come from glaciers in the Mt. Eddy and Parks Creek area.
Could this glacial outwash have been a factor in the creation of these mounds? Some glacial outwash is rich in tiny clay particles. Folks familiar with Shasta Valley know about this soil’s nasty characteristics! First, you should never drive off a paved or graveled road during wintertime! And second, both seasonal freezing and thawing and moistening and drying cause the soil to crack and heave. Many roads in Shasta Valley show off this result by their multitude of cracks and potholes.
Some scientists thought that after many years of freezing and thawing, with occasional earthquake shakes, these mounded features could have formed. Others studying these features were skeptical of this explanation. They pointed out that other locations having mounds were not covered by glacial outwash and where freezing and thawing did not occur to a significant degree. Not only that, but many mounds throughout the world are found on sloping land, not flat ground. The mystery remains–what could have caused these similar looking mounds to be formed in locations having significantly different conditions?
Having had a career in the world of science I am amused to run into situations where simple scientific explanations just don’t seem to fit! Science and scientists are often portrayed as almost God-like in their knowledge and wisdom. Throw a question or a problem out to a scientist and he or she will throw back the answer or solution.
In the case of the mound creation is it possible that there might be many ways that they were formed? Perhaps the mounds in Baja California or Missouri or South Dakota were not created the same way as the mounds we see at Edgewood!
Nature is complicated, certainly too complicated for our small brains to comprehend. Another complication is that nature often seems to “work differently” in one area or situation than in others. Maybe the presence of these Mima Mounds helps us appreciate our own intellectual limitations and nature’s variability.
Recently I asked my geologist friend to come with me on a field trip near Macdoel. After a nice drive we reached the area we planned to explore. It was a place I thought we might see impressive evidence of glaciers from thousands of years ago. After climbing a slight slope above the access road we were surprised to view a large flat covered by almost perfectly rounded mounds! Around each precision-formed hump was a ring of stones so consistent in width and appearance that they could have been hand-placed pathways. “Mima Mounds”, my friend muttered. “I haven’t seen this group before or any other area where they are so uniform in size.” We spent more than an hour exploring the flat where they resided, marveling at their beauty and symmetry.
Mima Mounds can be found in several Siskiyou County locations, but part of life’s fun is exploration—so I won’t cheat by telling where the ones I know of are located. If you stop to view the mounds near the Edgewood Rest Area, keep in mind the interesting geological story on display. Look around you. Thousands of years ago the area looked very different, with the snout of glaciers not far away and with layers of mud and debris covering the site. Sometimes as I drive by the area I wonder, maybe we don’t need to know how they were formed. Other times I consider the possibility that they may be proof that UFOs have landed.
