Above and below: eroded slot in Sevier River Formation near Castle Rock Campground, southern Utah (click photo above for better view of contents).
Base of coastal live oak, Montaña de Oro State Park on the Central California Coast:
Deep crack in outcrop of ash-flow tuff, Hickison Summit, central Nevada:
Pocket in rhyolite at The Honeycombs in western Utah:
And there are many more:
UPDATE: The answer to this geo-challenge can be found here.
