Adventure writer Mark Jenkins explored the world's biggest cave in Vietnam while on assignment for National Geographic. Jenkins, who is a University of Wyoming writer in residence, will travel the state to discuss the experience. (courtesy Mark Jenkins)

The light appeared suddenly in the dark, streaming from a sky that adventure writer Mark Jenkins hadn’t seen for several days. Had they already reached the end? he wondered.

But as he approached the light cascading from hundreds of feet above he realized it was a doline — a skylight-like feature created when the surface collapses over a cave.

Halfway through the cave Mark Jenkins and the team discovered a doline, a skylight in the roof of the cave. (courtesy Mark Jenkins)
Halfway through the cave Mark Jenkins and the team discovered a doline, a skylight in the roof of the cave. (courtesy Mark Jenkins)

Below it a miniature rain forest flourished, nurtured by the sunlight and precipitation entering through the opening. Jenkins, who lives in Laramie, found himself moving from total darkness, mud, rock and water, into a rare, subterranean world of sunlight, trees, monkeys and butterflies.

“It was fantastic and kind of extraordinary,” he said.

In 2009, Jenkins, a contributing writer to National Geographic magazine, joined a team of British spelunkers in Vietnam as they explored what would turn out to be the biggest cave discovered in the world.

Jenkins, who is also a writer in residence at the University of Wyoming, will travel the state this spring, talking about the cave and its geology, Vietnam’s culture, the Vietnam War and its aftermath, and the select group of adventurers known as British cavers. His talk, “Vietnam Underground: The Viet Cong, Spelunkers and the Biggest Cave on Earth,” is part of the university’s Global Studies Excellence Initiative’s “World to Wyoming” outreach series.

A Vietnamese man named Ho Khanh discovered the cave, called Hang Son Doong, in the 1990s while scouting for British spelunkers Howard and Deb Limbert.

Mark Jenkins, who writes for National Geographic, will tour Wyoming to discuss his trip to Vietnam where he explored the world's biggest cave. (courtesy Mark Jenkins)
Mark Jenkins, who writes for National Geographic, will tour Wyoming to discuss his trip to Vietnam where he explored the world’s biggest cave. (courtesy Mark Jenkins)

The Limberts attempted to explore the cave several times, but retreated before reaching the end. They realized they’d need more ropes, equipment and porters. They sensed they were on to something big.

Vietnam is known for its massive caves, Jenkins said. Water once covered most of the region. Tectonic forces lifted the limestone out of the water creating mountains. The uplift fractured the earth and the massive amount of rain the area receives seeps in, feeding underground rivers, which dissolves the limestone to create the massive caverns.

The team traveled through another cave called Hang En for half a day. When Jenkins emerged it was like entering a lost world of thick rainforest encircled by mountains. Dense foliage covered Hang Son Doong’s entrance. Without a local guide they wouldn’t have seen it, Jenkins said.

The team hiked about 50 yards in and then it was time to rappel. As the team descended several hundred feet, they didn’t know how big the cave was or how long they’d be underground.

“It’s exploratory,” Jenkins said. “They didn’t know what they were going to find. You just go. That’s the beauty of exploration and there’s not much left in the world.”

A few years before the Vietnam trip Jenkins wrote about cavers in Tennessee. The story required him to squeeze through tiny, muddy holes so tight he worried that if he breathed too hard and his chest expanded he might be stuck forever. That trip, along with his canyoneering experience, served as his training.

Jenkins isn’t a caver. He’s a mountaineer. Caving is mountaineering’s opposite. On a mountain Jenkins works up toward open space. Caving requires descending into a walled space of darkness. Yet both sports require the same rope-handling skills, just in reverse order and, while in a cave, in the dark.

The cave descent was slick with mud and required rope work similar to canyoneering and mountaineering.
In this photo, Gareth “Sweeny” Sewell leads on a 200-foot wall nicknamed the Great Wall of Vietnam.  (courtesy Mark Jenkins)

“You definitely feel you are entering the bowels of the earth,” he said. “It definitely feels like you are going down the mouth of something.”

His headlamp sliced the blackness only a few feet in front of him while exploring Hang Son Doong. The darkness of a cave is a darkness few experience. No starlight. No industrial glow in the distance. No moonlight. He couldn’t see his hand when he waved it in front of his face. The darkness was so thick it felt tangible. There is no sense of space, and direction becomes distorted.

“It’s a darkness unlike anything on the surface of the planet,” he said.

To explore the length of Hang Son Doong the team followed the underground river that carved the cavern inside the mountain. The topography forced the team to use ropes to cross the river. It took a week to navigate about 2.5 miles of the ever-changing terrain.

The cave is the biggest ever discovered, a title based on circumference.

The world’s longest cave is Mammoth Cave in Kentucky spanning more than 400 miles. The deepest cave in the world is Krubera-Voronja in the country of Georgia which sinks more than 7,000 feet.

Before the cavers explored Hang Son Doong, Deer Cave in Malaysia held the title of the biggest cave in the world.

Hang Son Doong spans 300 feet across and opens to more than 600 feet tall for more than two miles. The team measured it with lasers, Jenkins said. It’s big enough that a 747 could fit inside.

“We did the first descent of the Everest of caves,” Jenkins said.

When they saw the light on the last day they thought it might be another doline. It was the end. A big wall of mud about 200 feet high blocked their exit. They ascended the slick face and emerged into daylight.

Jenkins and the team explored the main body of the cave, but side passages remain untraveled. These are especially dangerous to explore, Jenkins said. If you lose your light or sense of direction you might never find your way out.

But it’s amazing to think, Jenkins said, that while all the mountains have been climbed and the continents mapped, there are still caves left to explore.

See Mark Jenkins present “Vietnam Underground: The Viet Cong, Spelunkers and the Biggest Cave on Earth,” part of the University of Wyoming’s Global Studies Excellence Initiative outreach series:

Laramie – March 3, 7 p.m., College of Education auditorium

Gillette – March 10, 7 p.m., Presentation Hall at Gillette College

Sheridan – March 11, 7 p.m. Sheridan Junior High School’s Early Auditorium

Powell – March 12, 7 p.m., Northwest College’s Yellowstone Building conference area

Cody – March 13, 7 p.m., Buffalo Bill Center for the West’s Coe Auditorium

Jackson – March 15, 3 p.m., Teton County Library

Lander – March 18, 7 p.m., Lander Valley High School auditorium

Rock Springs – March 19, 7 p.m., Western Wyoming Community College, Room 1302

Casper – March 24, 7 p.m., Casper College’s Wheeler Concert Hall

Kelsey Dayton is a freelancer and the editor of Outdoors Unlimited, the magazine of the Outdoor Writers Association of America. She has worked as a reporter for the Gillette News-Record, Jackson Hole News&Guide...

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  1. I had the pleasure of hearing Mark Jenkins speak at Casper College. His presentation is world class. Jenkins is one of the best public speakers I have heard. Its well worth your time .

    Doug Cooper
    Casper, WY