Near Littlerock in Thurston County, Washington — The American West (Northwest)
What We Know for Sure
Evidence of Ice Ages Beneath the Mounds
About 2.2 million years ago as earth’s climate cooled, massive ice sheets formed far to the north. These glaciers advanced southward and melted northward many times. Thousands of feet thick, they gouged underlying land and picked up immense loads of gravel and rock.
The last advance of ice into western Washington ended about 16,500 years ago. Mima Prairie is at the edge of its southernmost reach.
As the glaciers retreated, torrents of meltwater fanned across the landscape and deposited a load of gravel and rock. This gravelly outwash became the well-drained, dry soils of today’s prairies.
What is a Mima Mound?
Mounded landscapes are found in several areas of North America and in a variety of habitats. They are called pimple mounds near the Gulf of Mexico, prairie mounds in the northern Great Plains, and hogwallow mounds in California. Mounds in each location may have a unique origin.
In South Puget Sounds, Mima Mounds
They appear to be restricted to a single terrace level along the Deschutes River south of Olympia. Mounds are circular or elliptical 8 to 10 mounds per acre. Mounds are usually about the same size and shape in any one area, but some very lot mounds are found among larger mounds.
Erected by Washington State Department of Natural Resources.
Location. 46° 54.271′ N, 123° 2.918′ W. Marker is near Littlerock, Washington, in Thurston County. Marker can be reached from Waddell Creek Road SW 0.4 miles south of Deer Tail Road SW. Touch for map. Marker is located in Mima Mounds Natural Area Preserve in a kiosk that is a short walk from the parking lot; the above directions are to the intersection of Waddell Creek Road SW and the driveway to the Mima Mounds parking lot. Marker is in this post office area: Littlerock WA 98556, United States of America.
Other nearby markers. At least 8 other markers are within 12 miles of this marker, measured as the crow flies. Mima Mounds: The Mysterious Work of Nature (here, next to this marker); Scientists Still Search for an Answer (here, next to this marker); Mima Mounds: A Special Prairie (here, next to this marker); Ecological Connections Crosby House (approx. 10½ miles away); The Lone Tree (approx. 11.1 miles away); The Medal of Honor Monument (approx. 11.4 miles away); POW AND MIA Monument (approx. 11.4 miles away). Touch for a list and map of all markers in Littlerock.
Also see . . . Mima Mounds: Mystery hides in vast prairie. Newspaper article from the July 6, 2008 edition of the Seattle Times. (Submitted on February 16, 2014.)
Categories. • Natural Features •
Credits. This page was last revised on June 16, 2016. This page originally submitted on February 16, 2014, by Duane Hall of Abilene, Texas. This page has been viewed 288 times since then and 17 times this year. Photos: 1, 2, 3, 4. submitted on February 16, 2014, by Duane Hall of Abilene, Texas. 5, 6. submitted on February 15, 2014, by Duane Hall of Abilene, Texas.
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