HONOLULU (KHON2) — The Hawaii Volcano National Park has closed Nāhuku lava tube after data from a crackmeter showed a fracture near a large overhanging rock slab at the apex of the lava tube narrowing since Saturday.

They report the narrowing movement can indicate the crack is adjusting in response to other types of fractures widening in the lava tube. This can make the large overhead chunk of rock unstable and potentially dangerous. 

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Hawaii Volcano NP said these movements of a large rock slab are unusual in the monitoring record. They are looking to conduct further monitoring to determine if the lava tube can safely reopen.

It’s not clear how long the Nāhuku lava tube will be closed. A return of movement similar to the previous record would need to occur before the lava tube would be considered safe to reopen.

Nāhuku is a very popular destination when visiting the big island and hiking throughout Hawaii Volcano NP. It is considered an easy hike with breathtaking views.

Large rocks in Nāhuku were dislodged during the 2018 eruption and summit collapse of Kīlauea volcano. Hawaii Volcano NP said two crackmeters were installed in the lava tube’s ceiling to monitor their movement. 

Prior to the fractural changes over the weekend, data from the monitors revealed little change to the cave’s structural integrity.

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The restrooms near Nāhuku and the parking area remain open. For more information about this closure head to their website.