Nāhuku Lava Tube

Nāhuku, also called Thurston Lava Tube, is a short cave walk reached through native rainforest in Hawaiʻi Volcanoes National Park. The tube formed about 500 years ago as a river of lava cooled and drained, leaving an underground passage. It is a quick way to see the shape of an old lava flow from the inside, and an easy addition to a Kīlauea Iki visit.

Several parts of the tube have low ceilings. The ground can be damp, with uneven spots, so wear sturdy shoes and watch both your head and footing. The entrance has steps, and this is a developed cave walk rather than a smooth indoor passage.

A lava flow can cool into a crust while hotter lava keeps moving underneath it. When the eruption ends or the flow changes course, the remaining lava drains away and leaves a hollow conduit. Nāhuku is that plumbing left behind, with the route following a passage made by moving lava.

Nāhuku is translated as “the protuberances,” possibly a reference to lava drippings that once hung from the ceiling. Souvenir collectors removed them after politician Lorrin A. Thurston publicized the cave and drew more visitors. The older name Thurston Lava Tube still appears alongside Nāhuku.

The path to the cave passes through native rainforest, a good place to pause for native bird calls before heading underground. Inside, the orange lamps pick out the tube’s curved walls. For a photo, include a bend and a few of the lights so the tunnel’s depth reads clearly.