monument to the memory of the Modoc People, and as a great place to see basalt flows. But one of the other big reasons the monument was established can be seen in the picture below.
What? You don't see anything except piles of boulders? They actually actually reveal a bit of the inside of a volcanic system. Not the really deep stuff, but the plumbing system that allowed molten basalt to flow many miles without solidifying. The picture below is of a collapsed lava tube system. The park has many others that haven't yet collapsed.
In some rare instances, the fractures are blocked and water accumulates in the bottom of the cave. During the winter, cold sinking air freezes the water, and the cold air remains in the bottom of the cave all through the summer. The ice persists all year.
The caves of Lava Beds are fascinating. Some provide micro-climates where ferns and other unusual biota survive, despite aridity of the high desert environment. Others are full of ice (and are so fragile that tours are only offered in winter, since the warmth of people can cause melting). Quite a few have multiple levels, as one lava flow followed another. Post Office Cave has at least five of these levels, and Skull Cave has three. A large number of animals and insects live in the caves, including several endangered bat species (all bat species in the country are endangered by White-Nose Syndrome, which is spreading west from caves back east).
The park service has provided a pleasant campsite among the juniper trees, and a newly constructed visitor center. They sell cheap bump hats, and loan out flashlights for visitors to explore caves.