What is the world's longest lava tube cave?

The world's longest lava tube cave is Kazumura Cave on Hawaiʻi Island. Its surveyed passages extend for roughly 40.7 miles, or 65.5 kilometres, and the same volcanic system is also regarded as the world's deepest lava tube.

Kazumura formed in the ʻAilāʻau lava flow on the eastern slope of Kīlauea. The flow originated from Kīlauea Iki Crater about 500 years ago. As lava continued moving beneath a hardened surface crust, it drained away and left behind a long, branching tunnel system. Later collapses created many entrances and skylights.

The modern cave is the result of connecting passages that were once treated as separate caves, including Upper Kazumura and Old Kazumura. Cavers expanded tight links and surveyed additional branches, with major mapping work in the 1980s and 1990s establishing its record length. Kazumura is not a single simple corridor: it has more than 100 entrances, varied passage sizes and sections that range from easy walking to difficult crawling.

A common mix-up is confusing lava tubes with the world's longest caves of any geological type. The broader record belongs to Mammoth Cave in Kentucky; Kazumura's record applies specifically to lava tubes.