Much of Thurston County’s landscape was shaped by glaciers, melting or otherwise. So, while the Mima Mounds may be cool, there are other totally awesome features that you should take notice of.
1. For example, did you even see before that southeast Olympia is basically full of small lakes that were created by massive chunks of broken off piece of glacier? Lakes, created by massive pieces of ice.
Some Kettles from Southeast Olympia (from Geodata):
Can you imagine the block of ice that created Ward Lake?
How Kettles form:
2. So, in addition to dropping massive pieces of ice making massive holes in the ground, melting glaciers also created rivers that don’t exist anymore. And, if you look closely, you can find out where these old river channels are. Probably the easiest to spot is Spurgeon Creek just south of Lacey.
You can see exactly what I’m talking about on Spurgeon Creek Road, just south of the intersection with Fox Ridge Lane. To the west, you can see the Spurgeon Creek valley. But modern Spurgeon Creek is much too small for its creek valley. After the last time glaciers retreated from here, they created a massive meltwater river that carved the valley, eventually meeting up with the glacier swollen Chehalis River.
This detail of this map show exactly how the water flowed in the ancient Spurgeon Creek.
The Washington Landscape Blog has a great explanation of how these glacier meltwater rivers were different than today’s:
One is the lower Chehalis occupies a valley that it did not carve. The Chehalis follows the former valley of a much larger river. During the maximum ice extent during the last glacial period melt water from the Puget lobe ice sheet drained to the ocean via what is now the Chehalis River. The river that carved that valley was a much bigger river than the Chehalis.
3. Lastly, there is at least one massive rock that was brought to Thurston County by a freaking massive sheet of ice. Glacial erratics are pretty awesome on their own, and there seems to be plenty in the Puget Sound area.
So, I don’t know if it’s just me, but I think it’s pretty cool that we have one here.
The massive rock brought here by a sheet of ice is pretty far out of town on 153rd Avenue off of Vail Road.
|It’s a Massive Rock brought here by a Massive Sheet of Ice!
|An old photo of the erratic from “
|The Natural History of Puget Sound Country”
|by Arthur R. Kruckeberg
|One last shot of the erratic, from “Ground Water in the Yelm Area Thurston and Pierce Counties Washington,” USGS, 1955.
And, here, as an extra special bonus is a tour of the three geologic features that are more awesome that Mima Mounds.