A popular lava tube in Hawaii Volcanoes National Park has reopened following data monitoring and inspection of a fracture near a large overhanging rock slab at the apex of the lava tube.
Park management closed Nahuku — formerly known as Thurston Lava Tube — on July 30. Data from a crackmeter inside the lava tube revealed that a fracture near the large rock slab in its ceiling had narrowed by 2.47 mm.
Previous crackmeter movement was less than 1 mm since November 2019.
The data collected during the 18-day closure demonstrated a return of movement similar to the previous record. This data, combined with expert analysis and a physical inspection, allow Nahuku to safely reopen. In addition, the daily average velocity, the speed at which the crackmeter is either expanding or contracting, has been below the velocity thresholds established by the National Park Service as normal in Nahuku since monitoring began in 2019.
“Conditions are constantly changing on this living lava landscape, but safety is always our top priority,” said park Superintendent Rhonda Loh. “We appreciate everyone’s patience as we monitored the fracture and collected data from Nahuku.”
Entering any lava tube or cave is not without risk. Potential hazards include rockfall, low ceilings, standing water, tripping hazards, low light or no light. Large rocks in Nahuku were dislodged during the 2018 eruption and summit collapse of Kilauea volcano. Two crackmeters were installed in the lava tube’s ceiling to monitor their movement.
Visitors should always plan ahead and check the park website for the latest conditions and stay out of closed areas.