The Mima Prairie Mounds Just South of Olympia, WA

Just some photos of the Mima mounds at Mima Prairie, just south of Olympia, WA at the south end of Puget Sound. Spacial scale is roughly the same as those in Umtanum, WA (although the cause of formation is probably different). Ballpark scales are ~1m high, ~5m in diameter, ~10-20m center-to-center spacing. These values vary of course, but the mounds are remarkably spacially consistent, as seen in the aerial photos below.
 

View from the Mima park interpretive center (photo: A. Ganse)

 

View from the Mima park interpretive center (photo: A. Ganse)

 

Closeup aerial view of Mima Prairie mounds. Note directionally preferenced teardrop shapes of these particular mounds (not all have this feature). (photo: Seattle Times, 1977)

 

Mima Prairie. (photo: Arthur M. Ritchie, from Lasmanis, Raymond, 1991, "The geology of Washington", Rocks and Minerals, v. 66, no. 4, p. 262-277, reproduced on a website of the WA State DNR).

 

Old WA State DNR aerial photo showing the gravel pit (light colored blobby structure just off road at bottom) at which you can see cut-away views of mounds. The horizontal road is Bordeaux Road and the vertical one is Mima Road - if you follow Mima Road to the north (up) you head toward the interpretive center. (photo: WA State DNR)

 

Zoom of the above aerial photo. Note both here and above that the dark blobs are trees - the fact that they take up approximately the same horizontal scale as the mounds is a consideration of the tree-root hypothesis for the mounds' formation. (photo: WA State DNR)

 

2000 aerial photo of interpretive center at Mima Prairie (north of the gravel pit), found upon entering control point "613" into the Thurston County Geodata Viewer, turning on the aerial photo layers, and zooming and panning a bit. (photo: Thurston County)