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Into the Darkness

Try to imagine complete and total darkness.

Your room at night with the lights off? Doesn’t count. Because within seconds, your eyes adjust, and you can make out familiar shapes. Within minutes, you can probably walk around without bumping into anything. Maybe there’s the tiniest bit of light coming from under the door, or from behind the window shades.

So instead, imagine not being able to tell the difference when your eyes are open and when your eyes are closed. Literally, not being able to see your hand in front of your face. Imagine waiting several seconds…minutes…and your eyes never seem to adjust.

That’s what it’s like in a cave. At least until you turn your headlamp on.

The guys of Troop 382, Idaho Falls, Idaho, got their taste of the dark, the light and everything in between on their caving expedition to nearby Craters of the Moon National Monument last year.

Walking (and crawling) around in the darkness of Arco Tunnel requires preparation and patience. The last thing you want to do on a high-adventure trip like this is to go in unprepared, only to realize you’re in over your head.

Only the Beginning

From above, the entrance to Arco Tunnel looks like nothing more than a small tear in the ground. Once you scramble down a short, jagged slope, you realize the tear is tall enough to walk through.

About 30 feet into it, a gate blocks the tunnel from the casual park visitor. Troop 382 got the key to the gate by getting a permit from the park service, which allows only properly trained cavers into this particular lava tube. About 300 feet into it, the ceiling lowers so dramatically that you have to crawl. These guys trained back home in part by crawling under a long row of chairs that zigzagged back and forth. The entrance to Arco isn’t long, but some of the passages inside contain longer, very tight squeezes. These are the areas where your helmet really comes in handy. “You definitely have to watch what you’re doing, determine if it’s safe and use a lot of teamwork,” 12-year-old Scout Andrew Hartel says. “We found a few areas where you have to belly-crawl through. “The most important precaution is your helmet. I hit my head every time I go in.” Early on, the guys notice the harsh walls, ceilings and floors. If you lightly scrape your skin against any surface of the cave, you will get cut. That’s why Troop 382 leaves no skin exposed except for their faces. “It can be rough,” Andrew says. “Gloves are important, and so are boots.”

Harsh Conditions

The passageways of Arco Tunnel add up to 5,805.6 feet, a little more than one mile. Sections dip as far as 30 feet under ground. (But there are thin cracks in the floor of the cave that appear to go much, much deeper. Don’t drop your flashlight in there.) The Scouts divide into patrols and explore most of the tunnel. Some passageways are no more than a foot tall. Some rooms are as tall as a house. About three-fourths of the way to the back of the cave, the Scouts crawl up a 50-foot slope on their bellies the whole

way. The reward is a larger room with mineral deposits. The deposits — called sulfate compounds — look like snow. “You could have sworn it was snow, but when you poked it, it was hard as a rock,” 12-year-old Scout Nathan Marshall says. Every surface of the cave seems to be covered with tiny spikes. Traditional backpacks won’t last in these conditions, so the Scouts bring “pigs” with them.

The pigs are created by taking two empty one-gallon jugs and cutting off each bottom. After filling each jug with necessities (snacks, first-aid kit, two other sources of light and water), the two jugs are tied together to make a hardy pack that can handle getting scraped against the walls or dragged when the cavers have to crawl. When it’s time to take a break, the guys sit down and turn off their headlamps…and enjoy the complete darkness. “It was really dark, but I thought that was pretty interesting,” 12-year-old Scout Adam Armour says. “It turned out to be a blast.”


1. If you have claustrophobia, don’t go into caves. There can be some very tight spaces.

2. If complete and total darkness freaks you out, don’t go into caves. It’s hard to describe “cave darkness” until you’ve experienced it.

3. There is no active stream in Arco Tunnel. That means you either have to pee in a water bottle and carry it out or hold it in. (Note: Once you pee

in a bottle, it’s best to mark it so you don’t, you know, get confused.)

4. Wear a helmet with a headlamp. You will bump your head, and the cave’s ceiling and walls are extremely rough. It also leaves hands free for balance and for crawling.

5. Wear old, sturdy pants, such as blue jeans, and a heavy long-sleeve shirt. Wear work gloves and tough shoes. The harsh conditions will tear lightweight clothing to shreds. Elbow pads and kneepads will come in handy.

6. Wear lightweight long underwear. The Arco Tunnel temperature is 45 degrees.

7. Always cave with an experienced caver, and make sure a responsible adult knows where you are going and when you will return.

8. For safety, cave with a group of at least four people.


Arco Tunnel, like the other caves at Craters of the Moon, is not like the limestone caves with which most people are familiar. It’s a lava tube, formed by the long-ago eruption of a volcano. Starting 15,000 years ago, scientists say, and continuing off and on until as recently as 2,000 years ago, boiling lava erupted from the earth near Arco, Idaho, and covered the area. As the lava fl owed, it cooled and hardened fi rst on the outside, forming a tube through which the still-hot liquid lava could flow. When the eruption was finished and all of the lava cooled, some of the tubes were left with hollow, branching sections like an underground maze. Limestone caves, on the other hand, are formed by rainwater that seeps through the ground and, over millions of years, erodes limestone rock that lies deep underneath. First, the water causes cracks to form, then tunnels, then entire rooms. Most limestone caves are still growing, though it would be thousands of years before anyone could tell the difference. Lava tubes, on the other hand, are finished, assuming there isn’t another volcanic eruption. The volcanic area around Craters of the Moon is not extinct. Scientists believe another eruption will occur sometime in the next 1,000 years.

2 Comments on Into the Darkness

  1. I like it

  2. Pyro Maniac // June 4, 2007 at 10:14 am // Reply

    My troop motto is Sempur peradus which means always prepared. I have athousand flashlights and I have bright headlights. which light up the cave.

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