This geological feature MUST be added to your list while in the area. When I first discovered this spot, I could hear voices inside my head that kept whispering "plant cache, plant cache, plant cache". So, out of obligation to whatever geocaching spirits have possessed my brain, I stopped the vehicle and immediately found the best hiding spot I could muster.
You are searching for a standard sized container and should find it with a fair amount of work. I stuffed it with a few things I had remaining in the back of the truck at the time.
Even though there is little chance that someone will accidentially stumble upon this cache, please place the cache and its cover materials the way you found it, or better, to help preserve the hide for the next seeker. The cache should not be exposed at all by design.
This geocache was not meant to be too easy so if you have physical limitations or are claustrophobic, you might want to pass on making the find.