Lava Beds National Monument, dubbed the land of burnt out fires, has over 700 caves. Lava Beds park is a high desert wilderness. It can get very hot here in summer. You want to take a cool dip? You can have it right here. The air temperature in the caves is about 55 °F (13 °C) year-round and the temperature in ice caves is even lower. There are caves to be entered via staircase or ladder. Each step down into a cave increases the physical chill. The handrails almost turn icy. Then, climbing up and out may give you some sort of a heat shock.
A nice cave to start your hot-cold experience is the Mushpot Cave. Mossy rocks are overhanging its entrance.
This 770-foot-long underground tube is only a 524-foot-walk away from the visitor center—where you should stop first to get informed about the diverse caves in the park and their various levels of challenge. The Mushpot has a relatively smooth, paved path. If you are tall, be prepared to duck-walk in some places. A hard hat may protect your head, but also makes you taller. While stepping down into the Mushpot hole you will notice the spongy and soft moss covering the surface of the upper-cave twilight zone. Inside the lava tube, you will walk along a lighted path guiding you through and back between narrowing walls and interesting formations—assisted spelunking.
Don't expect other caves to be illuminated. Bring good flashlights. Skull Cave (2.4 miles from the visitor center) has a relatively large entrance. Daylight “lasts” for a while along the downhill path past its opening mouth (see top picture), but you need artificial lighting towards the tube's end to explore the ice floor. The cave is named for bones found inside: two human skeletons, bighorn sheep skulls and bones of antelope and mountain goats.
Another interesting underground biotop is Merrill Cave, 2.8 miles away from the visitor center. A handrail staircase leads into it.
Its ice floor is the stage of legends. Rather than being a cave of the dead, this ice cave has seen lively entertainment. Visitors in the early 1920s skated on its ice floor by lantern light. Today, global warming is dimming the chances of cave ice parties in the future:
"In 2000, Merrill Cave's massive, thick “ice rink” began to rapidly melt. The more ice melts, the warmer the cave becomes. Consistently cold winters, along with rain and melted snow dripping from above, are necessary to sustain ice throughout the year. Though natural shifts in conditions play a role, you can now see the effects of global climate change in ice caves at Lava Beds. Average annual surface temperatures have risen about two degrees over the last six decades, while average precipitation levels have fluctuated greatly. These factors have contributed to a dramatic loss of ice in the majority of monitored caves. If trends continue, could the ice caves at Lava Beds someday lose all their ice?" [Text from panel at Merrill Cave's entrance]
Global climate change can be monitored right here at Lave Beds. Or is it only a limited microclimate change in a remote area of northeast California?
More to explore at Lava Beds
References and further reading
 National Park Service: Lava Beds Caves.
 Lava Beds National Monument: The Path Less Beaten.
 Edward Brook, Lacey Little and Shane Fryer: A Preliminary Investigation of Cave Ice at Lava Beds National Monument, norther California. Available as report in PDF format.