The Nahuku lava tube (also known as Thurston Lava Tube) reopened Aug. 17 at Hawaii Volcanoes National Park.
One of the few accessible lava tubes in Hawaii, Nahuku was created long ago by an underground river of magma and visitors have frequented the lava tube via a short day hike.
It was closed in early August due to movement of an overhead rock slab, which made the trail unstable and dangerous.
The National Park Service said the tube would reopen with a "return of movement similar to the previous record," which would be considered safe again. The park will continue to monitor its movements for possible future closures.
UPDATE: The tube is reopened, as of Aug. 17.