Under the Surface: Caves at Craters of the Moon


The landscape of Craters of the Moon National Monument is foreign and almost alien. It’s nothing like the rest of Idaho, with sprawling desert and grasslands and towering mountains and forests. Instead, Craters of the Moon looks barren and dead. A landscape covered in ancient lava flows and now dormant cinder cones. The land is covered in evidence of a time when this area was a glowing and burning lava field, with jets of fire and molten rock flying thousands of feet into the air.

Now, Craters of the Moon sits dormant. A quiet reminder of a more turbulent time when this was a hotspot of geothermal activity and eruptions. Walking across the trails through the 15,000-year-old lava fields makes it apparent why astronauts came here to study volcanic activity and geology in preparation for their moonwalk. And it’s easy to see why this is called Craters of the Moon. But, just like not all of the lava flows are ancient, the most recent are around 2,000 years old, the surface of Craters of the Moon isn’t all that this National Monument has to offer. And neither is it the most interesting.

400 Caves and Counting

While the general public might not have access to all of them, there are currently over 400 documented caves in Craters of the Moon, and more caves continue to be discovered each year. Even with the impressive amount of caves here, they all break down to three different types: lava tubes, fissure caves, and differential weathering caves.

Lava tube caves are the most common type of cave found in Craters of the Moon, and these will be the kinds that you’ll be able to explore. Lava tubes are created when the surface layer of a lava flow cools and hardens, forming a shell. This creates a kind of insulation for the molten river of lava still flowing, and sometimes these lava tubes can extend for miles underground. When the source of the lava is interrupted, or the flow is diverted, it can leave behind these empty tubes. The best example of a lava tube cave is the Indian Tunnel. You can get to this cave by taking the Caves Trail, and you’ll also have the chance to explore three other lava tube caves along the trail.

Fissure caves are found in the Great Rift. These caves can be found in the deep cracks of the rift. The King’s Bowl is the place to view fissure caves, some of which can get incredibly deep, including one that’s at least 650 feet deep. While you can explore these fissure caves, access is limited to the cavers that have the proper experience and equipment to do so.

Differential weathering caves are incredibly rare, and even more difficult to find. They are created when volcanic material is hollowed out by the elements. Wind, rain, and frost can create these caves.

Exploring the Caves

The best way to explore the caves at Craters of the Moon is by taking the Caves Trail. You’ll be able to explore four different lava tube caves: Indian Tunnel, Dewdrop Cave, Boy Scout Cave, and Beauty Cave. Dewdrop cave is small, and you’ll be able to see the majority of the cave from the trail. Indian Tunnel is the largest, and you’ll use stairs to enter the cave. If you don’t mind a bit of a climb and a small exit, you can walk through the entire cave and get back to the trail. Boy Scout Cave is an ice cave. There’s ice year round. You’ll have to crawl to get into this cave, and there might be water along the floor of the cave. It will be slick. Beauty Cave has a large opening and a slope to enter.

You will need a flashlight for all of the caves except the Indian Tunnel, and long pants and sturdy shoes are recommended. A helmet is also suggested, because some of the caves have low ceilings, but a hat might offer a little protection if you don’t have a helmet. Never go into the caves alone. And stay alert to signs marking hazards.

You will be required to be screened before entering any of the caves at Craters of the Moon, or any National Park Service land. There is a fungal disease that has been killing bats by the millions, so preventative measures are being taken. You’ll need to get a free permit to enter the caves, and you’ll need to tell them if you’ve been in any caves since 2005, and if so, if you have any of the equipment or clothing with you that you wore.




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