Spelunking in Michigan’s Longest Cave, the Hendrie River Water Cave

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The entrance to the Hendrie River Water Cave in the eastern end of Michigan’s Upper Peninsula is not easy to find – it’s off a remote paved highway a few miles west of Trout Lake, down a dirt road, an unmarked path and then through the woods and into a gorge. The ground nearby is pock-marked with pits, camouflaged by plant growth, but big enough to swallow a snowmobile or unwary hiker.

This is limestone country, where water erodes the ground and the Hendrie River has created what has been officially declared the largest cave in Michigan – a 620-meter-long (2,034 feet) cavernous passage.

I visited the cave twice one summer – both times guided by Tim Deady, vice president of the Michigan Karst Conservancy, which owns the 480-acre Fiborn Karst Preserve containing the unique eroded limestone outcrop characterized by the sinkholes, caves and disappearing streams of “karst” geology. These features formed during the past 10,000 years as acidic water from rain and a swamp dissolved the limestone.

We had been warned to bring knee pads, gloves, a helmet and three sources of light, two attached to the helmet.

Why two on the helmet? Because if one fails in a narrow tunnel, we might not be able to reach another in our pocket, Tim says. I assumed he must be exaggerating.

On the first trip, we stood around in our light shirts and old shoes, cheap flashlights duct-taped to our discount-store helmets while Tim suited up: heavy-duty canvas coveralls, sturdy waterproof pack, knee pads, high rubber boots, gloves, chin-strapped helmet. It was reassuring and unnerving at the same time.

We dropped into the gorge and entered a dark tunnel, a wide crack in the stone, big enough to walk into standing up. The air was cool and so still that water, slowly seeping down through the fractured limestone, clung in beads to the rough ceiling, glistening in the glow of our headlamps like thousands of tiny white Christmas lights. Droplets clung also to slender threads of hyphae, delicate fuzzy growths of fungus slowly devouring tiny bits of organic matter washed into the caves during high water.

In some places the passage was stomach-suckingly narrow and in others so low we crawled on hands and knees. The river was shallow but numbingly cold, and we were quickly soaked. Our too-large helmeted heads bumped walls and ceilings. Caverns opened up large enough for our small group to reconnoiter. There we turned off our lights and listened. The silence felt like a thick soft blanket. This must be what it felt like to be the toads we found in one cavern, meditating in the dark like miniature full-bellied Buddhas, perturbed by our noisy intrusion.

Tim says that visitors rarely feel claustrophobic while taking a tour. “The majority of visitors are people who’ve never been in a cave before. Usually they’re wide-eyed, looking around, saying ‘Oh wow.’ They’re too excited to feel uncomfortable.”

My senses were deceived underground. I couldn’t see the passages created by water, although they were right before me and even above me. An experienced caver from New York who was with us kept disappearing into invisible overhead tunnels and re-appearing farther on, poking his head from what looked to me like a solid wall.

Voices bounced and echoed in the jagged passages and sounded garbled as though spoken under water. Judging distances was impossible. My companions could have been a few feet or a few hundred feet away.

Because the cave is visited by relatively few people, I had the rare feeling of being an early explorer, that perhaps I’d see something important unnoticed before. Deep into the cave, we lowered ourselves over a waterfall and down into a room enlarged by the rush of water. The water had scoured the walls smooth, exposing a geological diorama – a coral reef developed 400 million years ago when warm shallow oceans covered this land.

For Tim, the most fascinating feature of the cave is that it exists at all. “This cave is special because it’s a young cave … started forming after the glaciers scrubbed everything clean. … It’s certainly the largest mapped cave in the state. The others I know of don’t come anywhere near its length.”

While the others continued to the Goop Loop – a narrow slit where small, non-claustrophobic people could belly-squirm inside – I enjoyed being alone, examining cave walls, looking for clues to the eons-old environment surrounding me. At chest level, blackened amorphous masses protruded from the wall, perhaps deposited by ancient currents. A perfect fragment of segmented stem was exposed.

At knee height, hand-sized growths of colonial coral rimmed with gold and black were polished as by a jeweler’s wheel, exposed exactly as they’d looked before being covered with silt during the Silurian Age, 400 million years ago when Michigan was closer to the equator. I was entranced.

Back on the surface, I felt bombarded by waves of energy. This must be how a newborn baby feels – emerging from the womb. The atmosphere buzzed – bugs trilled, branches creaked, pine needles and leaves rattled in the breeze. The air snapped and crackled and set my thoughts to the task I had yet to do that day – like hurrying back to my computer to study the Silurian reef to understand what I’d seen.

As we headed to our cars, we met young men from lower Michigan who’d heard of the caves and appeared awestruck by our muddy, exhilarated appearance and by the muffled voices from below our feet where two of our group were still in the caves.

Yes, I casually announced, we’d explored the caves, and they could, too. I directed them to Tim. I didn’t tell them that inside the cave they may be reborn with a deepened understanding of the world beneath and around them.

To Tour the Cave

The Michigan Karst Conservancy arranges guided trips through Hendrie River Water Cave. The cave is totally undeveloped; visitors should be prepared for rough conditions. Contact Martina Golden at goldencamp@comcast.net or 248-666-1683 for a permit form and additional information.

Leslie Askwith, retired from Chippewa County Health Department, writes, gardens, works with the local farmers' markets in Sault Ste. Marie.