Kazumura Cave

The longest lava tube on Earth was not discovered. It was assembled.

Kazumura runs 65.5 kilometres, 40.7 miles, down the eastern slope of Kīlauea, and drops 1,102 metres, which makes it the deepest lava tube as well as the longest. The rock it runs through is young: the ʻAilāʻau flow that contains it came out of Kīlauea Iki Crater around 500 years ago.

Its documented history starts unglamorously in 1966, when one of its entrances was designated a fallout shelter. By the early 1970s cavers were paying attention, after Francis Howarth found a new troglobitic moth in it, Schrankia howarthi. A British expedition surveyed 11.7 kilometres in 1981, and that alone put it among the longest lava tubes known.

Then came the joining. What is now one cave was several. Kevin Allred and Mike Meyer spotted a small connection between Upper Kazumura and Old Kazumura and enlarged it enough to get through. Paradise Park Cave was linked through a pile of breakdown, later stabilised with a culvert. Sexton Cave ended exactly where Kazumura began, and Mike Shambaugh dug through black lava rock until the two met. Kevin and Carlene Allred surveyed the combined result at 47 kilometres, which made it the longest lava tube in the world. Olaʻa Cave went in next, in 1995, followed by smaller caves near Old Kazumura, two of them joined by a crawlway you would not enjoy.

The Allreds put all of it into the Kazumura Cave Atlas, which by 2002 listed 65.61 kilometres of passage and 101 entrances.

Every one of those entrances is on private land. Hawaiʻi law requires asking the landowner before entering a lava tube on their property, so this is not a cave you turn up to. At least one owner has run paid adventure tours through his section.

The life down there is found nowhere else: a blind planthopper feeding on ʻōhiʻa roots, a cave cricket, a millipede, two moth species, an earwig and several spiders.