Civil Defense Caves

The Civil Defense caves, large tubes formed from lava, snake underground for thousands of feet. Because of lava’s insulating qualities, the caves’ interiors are cold even on the hottest days of the summer and there is usually ice at the entrance to the cave.

Bring jackets, good footwear, and flashlights.

North of the St. Anthony Sand Dunes, look for a tall, but small sign indicating the Civil Defense Caves are five miles on the dirt road heading east.

The road is traversable by passenger cars but drive carefully. After a rain storm the road can be muddy. It is easy to get lost because the road meanders up, down, and around and is not visible very far ahead or behind. After about three miles there is a fork in the road. Take the left fork. The road continues in a north, north east direction for about a mile. The road terminates in a open area that serves as a parking area. There are usually several fire pits in the area. The cave entrance is just to the north of the of parking area.

From the entrance the cave goes in two directions. The easiest section of the cave heads to the southeast underneath the parking area. Scrambling over the large rocks and fields of ice; the floor of the cave is generally flat, though not very smooth. Mostly there is ample head room. If you continue to the end you will occasionally have to scramble over large rocks that have fallen from the ceiling. The more adventurous can explore the narrow parts of the cave such as "Fat Man's Misery."

Lava tubes are formed when molten lava flows in a confined channel for days. The flows develop a solid crust or roof as the lava on the surface starts to cool and harden.

When the lava stops flowing, the lava in the channel eventually flows out, leaving a tube behind and a relatively flat floor. Lava tubes are common in eastern Idaho.

This is part of the online edition of Henry's Fork Country.

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