1. Large rivers of lava flow in natural channels of their own creation. Fast central currents keep the core hot, while the slower moving edges cool and thicken as they are exposed to cooler surface air. As the surface cools, the top of the flow crusts over from the sides, like the way ice freezes on a river.

2. The crust eventually joins completely and insulates an interior flow. When fully insulated, the flow becomes superheated.

3. The superheated lava flow then begins “downcutting” through the ground or lava flows beneath it, in a process known as thermal erosion. This results in a deeper, narrower cross-section.

4. When the eruption stops, lava often drains from the tube and leaves behind the vacated conduit beneath the surface. Dripping formations may begin to develop as the lava level subsides. It may take about a year for the tube to cool down, but soon the new underground passage will be colonized by insects, spiders and their cave-dwelling kin.

For Native Hawaiians, these caves have also had great cultural importance. They could be used as shelter from both the elements and human enemies. Food stored in the cooler, more thermally stable lava tubes would last longer. Middens within lava tubes have contained ʻopihi shells, stone tools and other evidence of daily life, testifying to their usage. Because most of the island of Hawaiʻi has no standing lakes, ponds, or flowing streams, drinking water could be hard to find. Lava tubes were one valuable source. Dripping water from the ceilings, filtered down through porous lava rock, was often gathered in gourd bowls called ipu. Lava tubes were also central in some ceremonies and burials. The carefully prepared and wrapped bones of imporant individuals would sometimes be placed in the caves. The national park protects these sacred burial caves and no tours or entry is permitted.

P.O. Box 52 Hawaii National Park , HI 96718

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