Friday, much of this area is covered with very permeable lava flows. Rain and snow melt goes directly into the ground, to re-emerge as springs at Clear Lake and elsewhere along the Upper McKenzie River. Here, apparently, the tephra seen in Fridays post, and the lacustrine sediments visible in the sides of the hole above, create a less permeable cap and impounding the lake's water. I can't say what portion of the lake's summer water loss goes down these holes, and what infiltrates directly through the lake bed and into the underlying bedrock, but I doubt the holes account for all of it. That is, I expect the lake bed isn't entirely impermeable.
Route 20 runs through the notch in the horizon on the left, and along the south side of the lake.
Photo unmodified. September 7, 2016. ZoomEarth location. (Location approximate- can't resolve hole.)
Is This Your Hat?
2 years ago