If not perturbed by a few bumps and dirty tires, adventure-seekers traveling on a small muddy road northeast of the St. Anthony Sand Dunes will eventually come to a large hole looming in the ground.

With an entrance wide enough to back a truck into, the Civil Defense Caves

beckon to be explored.

The name of the caves dates back approximately 30 years when the Fremont County Department of Civil Defense used them as a fallout shelter and was issued a special permit from March 1971 to February 1981, according to the Bureau of Land Management.

"The Corp of Engineers surveyed the caves-shelters and figured more than 5,000 people could be sheltered in them," according to the BLM.

The basalt rock provides a good block for radiation, so federal officials

felt it would be a safe place to go in case of nuclear attacks. They even

widened the entrance of the cave to enable trucks loaded with supplies to

back inside.

"They thought it would be a safe place, but it's actually the last place I'd

go unless I took a big mattress," Ed Williams, who taught geology at

Brigham Young University-Idaho full-time for 40 years and is now teaching part-time, said.

The Civil Defense Caves, which stretch approximately 3,000 feet back into

the main cave, are actually large lava tubes that formed, estimated, more

than a million years ago from a nearby shield volcano.

"As you go out to the caves, you can see some trees on the skyline. That's

the summit of the shield volcano, which is approximately 30 miles across.

There are about four or five tube systems associated with that volcano, some 10 miles long," Williams said.

Lava tubes are formed when molten lava flows steadily in a confined channel for many hours up to days. The flows develop a solid crust or roof when bits of lava stick together and harden. If the molten lava stops rising from its source deep within the earth, the stream moving inside of the crusted-over tube will drain away and leave an open lava tube cave. The process is similar to a stream that continues to flow beneath the cover of its own winter ice, according to www.vulcan.wr.usgs.gov.

With the mouth of the caves facing north, the cold northern winter winds

blow inside, creating an overall chilly atmosphere. The warm southern summer winds blow over the top of the caves, so it remains below freezing year-round.

"A unique ecosystem thrives within the cave. You are surrounded by billions and trillions of living things," Williams said.

A white substance can be seen clinging to the rock in many areas of the

cave. While some of it exists as calcium deposits, the "squishy white stuff" is actually a bacteria that grows on the walls, Williams said.

"The bacteria doesn't seem to be harmful. I've gone in, touched the stuff

and then came back out to eat a sandwich. It didn't seem to hurt me," he

said.

Spiders, millipedes and a rare form of beetle that eats the bacteria and has completely adapted to living in the darkness can also be found in the cave.

The ceiling in the Civil Defense Cave varies in height. For the most part,

the ceiling is high enough to allow explorers to walk around comfortably.

Other areas, however, require one to shimmy between narrow slots of rock

until it opens up again. Williams, who has been studying the caves for about 35 years, mapped out the area and refers to one narrow spot as "Fat Man's Misery."

"I liked working our way through 'Fat Man's Misery' because it made it more of a challenge for us," Katie Erickson, a student attending BYU-I, said. "The very thought of getting lost in there made me hold onto my torch harder."

Hieroglyphics can be found splashed across the walls as past explorers left their mark. These drawings range from the creative (a white spray-paint telephone deep inside) to the daring ("Will you go to Prom with me?" scrawled near the entrance) to the peculiar, (a blazing orange outline of a

body with "Me" inscribed nearby).

Williams emphasized that these caves are very susceptible to damage.

"These caves are unique and can be ruined by a few thoughtless people who

spray paint walls and leave garbage," he said.

The Civil Defense Caves, with unique structures and interesting history, can provide an evening of exploration. Just don't forget a flashlight and

remember to wash the car after returning to civilization.