Ape Cave

Recently hiked Ape Cave, a lava tube formed during a fluid basalt eruption about two thousand years ago. The outside layer of lava cooled quickly, but the interior of the flow was insulated enough to stay molten and flow out from under the cooled section, leaving an empty tube a couple kilometers long, full of nifty cave slime and weird waterfalls made of solid rock that you somehow have to climb up or down. It is very dark under several meters of rock. The walls are uneven and glassy, and the shadows cast by your headlamps sink unevenly into the glass and take on three dimensions.

Not much to photograph, except the two places where cave-ins have made holes in the roof, all a-green and ferny.