After hiking the Inner Basin Trail the day before, we decided to take this short jaunt before heading back down the hill to the heat of the Valley.
The entrance to this 3/4 mile long cave is a couple of hundred yards from the parking lot. Formed by a lava tube, the entrance is actually a collapse of the roof of the cave. As a result the first part of the hike is somewhat difficult. A steep incline across large boulders leads you into the darkness of the tube below.
Once getting down into the tube, the 32 degree air is a refreshing change from the heat on the surface ... but bring an extra layer, because a few minutes down there and you'll definitely get cold.
The cave appears much like a subway tunnel, sometimes as low as 4 feet high, at others 30 feet high. Sometimes it narrows to 20 feet wide, other times opening to 50 feet wide. It's basically a simple tube, out and back, no way to get lost. There's one spur cave, but it returns back to the main tube. A map at the trailhead illustrates the cave.
The early part of the hike is more difficult because of unsure footing. Apparently, (from what I've read) as the lava was flowing, the cave was created by the lava cooling and hardening on the surface, while also insulating the remaing lava flow from cooling until it had drained from the tube...leaving an empty cave.
Large rocks and slabs are embedded into the floor of the cave, which also appears to be a hardened lava flow toward the end of the cave. Large crevasses in the floor cave occasionally make footing difficult.
Bring at least two light sources and extra batteries. If you lose a light in this cave, it would be virtually impossible to get back out unless somebody else came along. We had headlamps, and they proved to be the most convenient because there's a few times that it's nice to have two free hands. A camping lantern would also be a good idea for a more illuminated trip.
The temperature is constant year-round making a refreshing break from the summer heat. The trailhead is on forest roads that are open in winter, but snow can make accessing this spot difficult.
All in all, this is a nice quick trip - not so much a hike as an adventure. It's great for kids too, making a neat geology lesson.
As a note, my otherwise extra-happy-hiking yellow lab was not willing to go into the cave. The boulders at the entrance and the darkness and unsure footing were not to his liking - and I wouldn't recommend anybody try to bring a dog with them after having been there myself.