HAWAII NATIONAL PARK (KHON2) - One of its proudest claims is that it's open for visitors 24/7, 365 days a year.
But on Thursday night, and for the second night this week, Hawaii Volcanoes National Park closed to the public, and will remain closed indefinitely.
Last weekend, it was due to dangerous fumes. This time, park officials fear a steam explosion inside of Halemaumau Crater.
Only the Kahuku Unit will be open during its normal hours, Friday through Sunday, 9 a.m. to 3 p.m.
"Our concern is if the lava lake keeps dropping as it has over the last ever how many days, that the lava lake level could drop below the water table. If that happens, we're into a whole different situation," said U.S. Geological Survey Hawaiian Volcano Observatory geologist Janet Babb. "Groundwater can mix with the magma and it will produce steam, and that can result in steam explosions."
The last time that happened was in 1924. Pressure built up, followed by an explosion so powerful, rocks the size of cars were launched out of the crater.
While Babb doesn't expect to see that happen this time around, she says the potential danger is always there.
"Based on our models that we have right now, the situation, it is definitely possible of course, and with Mother Nature, we can never say anything for 100-percent certain," she said. "We know it's a possibility, and we're going to err on the side of caution to be prepared for this."
Scientists say the greatest fear with an explosion of this type is that they come with little or no warning.
The potential danger, they say, is far too great to allow people to remain inside the park.
"That's not because we're thinking it's going to be a life-threatening event," said Jessica Ferracane, Hawaii Volcanoes National Park public affairs specialist. "It's more of an inconvenience event, a nuisance, with ash and small pebbles that are going to be raining down here. Not the place that we want people to be."
For people outside the park, scientists says there's no need to worry about rocks flying out. However the ashfall could prove problematic.
In 1924, ash went to Hilo, Pahala, Makuu, and Hakalau.
Scientists say the ash particles can irritate your eyes and throat, and if it's falling in your area, stay indoors if possible.
"It will be a nuisance. It will not be life-threatening. You can see deposits of several millimeters, a centimeter or so, but still it can be a nuisance," Babb said. "It can disrupt water catchment systems, and if it falls on road and it's wet, the roads can be slippery. It can disrupt electrical transmission lines. There are a lot of hazards that go with ashfall, but they can be dealt with."