In 1880 and 1881, Mauna Loa—one of the mighty shield volcanoes composing the Island of Hawaii—unleashed a series of eruptions. An 1881 lava flow got plenty of attention as it streamed northeast toward Hilo Bay, nearly reaching the town of Hilo. Kaumana Caves is a rustic but popular site a few miles out of town offering a subterranean look at part of that flow’s remnants.
The “caves” are actually openings in a lava tube from that well-documented eruption. In the summer of 1881, the pahoehoe lava flow—variously forking into several streams that rejoined and split again—extended as far as about a mile from Hilo Bay. The story goes that Princess Ruth Keelikolani, a member of the royal House of Kamehameha, saved Hilo from the encroaching flow by praying to the Hawaiian volcano goddess Pele.
A lava tube is a tunnel formed when the outer skin of a lava flow cools and crusts over while the interior remains hot and molten. When the eruption ceases and the still-flowing inner lava drains away, a hollow center is left within the flow. The Kaumana Caves lava tube extends for more than 20 miles, though only a relatively small portion is open to the public. (More on that shortly.)
Reach Kaumana Caves, a county park, via the Kaumana Drive portion of Highway 200 (the Saddle Road) west of Hilo. This stretch of the road is actually partly built on the 1881 flow. You’ll find the signed parking area for the caves just past mile marker four. It’s on the other side of the road from the caves themselves, so be sure to use caution when crossing the highway.
Picnic tables and restrooms are available here, but not much else. A concrete stairway leads through a skylight: a place where part of the lava tube’s roof collapsed, opening up access. The mouth of the “cave” is dramatic. Nourished by sunlight, the lava-rock draped in tropical vegetation that includes ferns, impatiens, and philodendron as well as hanging roots. As you descend to the floor, though, you’ll see that sunlight allowed in by the collapsed roof doesn’t illuminate very far into the tube.
According to newspaper reports of the time, people actually came here to see lava streaming beneath the collapsed roof in 1881 while the flow was active. Must have been quite the sight!
It’s perfectly rewarding simply to make that stairway descent into the lava tube and peer into the darkening recesses. If you’ve brought along flashlights or headlamps—you want at least one backup source of light—and are wearing sturdy footwear, you can explore a little ways in.
But it’s important to note that this unlit, unimproved lava tube has stretches of treacherous footing. Furthermore, much of it lies below private land, and the boundaries between the county park and this privately owned acreage are unmarked. Therefore, you should confine your “spelunking” in the lava tube to a short foray.
From the skylight entrance, you can actually trek to the right or the left. The righthand tunnel is the broader one, while the lefthand way involves some tight passages. The mostly smooth pahoehoe floor of the lava tube (made rugged in places by fallen rubble) and the ornate formations of the walls and ceiling are fascinating to see. The stale, muggy air in the darkness adds to the mysterious vibe.
Whether you confine your appreciation of the Kaumana Caves to the entrance or journey a short distance in, this lava tube is quite mesmerizing. Practice caution and common sense during your visit, though, as such a place is inherently risky.
Avoid venturing into the lava tube if it’s been raining heavily recently. Some sections may be flooded in such weather.