HILO >> Lava from the Kilauea volcano eruption is still cooling down and estimated to be only halfway cooled, scientists say.

The U.S. Geological Survey’s Hawaiian Volcano Observatory said cooled exterior lava has insulated deeper areas of the lava flow, the Hawaii Tribune-Herald reported Saturday.

The exterior cooled because of exposure to air and rain, but the insulation is expected to keep some rock further below at extremely high temperatures for years, observatory geologist Carolyn Parcheta said.

Kilauea erupted in May 2018 and destroyed more than 700 homes on the Big Island.

Based on the average thickness of the lava of about 82 feet, Parcheta said there is a likelihood that liquid lava, or lava higher than about 1,500 degrees Fahrenheit, still exists in lava delta spots beneath the surface.

“If you were to cut the lava delta open and remove a piece of it, the lava inside would be liquid enough to flow to the ocean,” Parcheta said.

Observatory models based on lava flow thickness and rainfall amounts estimate flows could take three to four years to cool below the boiling point of water, Parcheta said.

In other words, “we’re about halfway there,” Parcheta said.

Lava could cause complications for reopening or redeveloping parts of the island’s Puna region where the eruption happened. Road repair crews encountered lava rock temperatures of up to 800 degrees Fahrenheit while working to reopen a highway.

The lava does not pose any significant risk in its current state, but there is no way to accelerate the cooling process, Parcheta said.

“Nothing’s pressurizing the lava, so if you drilled a hole down there, it wouldn’t come gushing out,” Parcheta said. “The lava’s not going to burst through the delta or anything like that.”