A quarter of Halemaumau Crater was filled with molten rock by midday Wednesday, and lava was pouring in at a rate of 1,412 cubic feet per second, according to scientists with the U.S. Geological Survey.

At that rate, it would take 18 days to completely fill Halemaumau Crater, USGS research geophysicist Hannah Dietterich told the Honolulu Star-Advertiser Wednesday evening.

That volume output rate, however, has slowed considerably from the more than 7,062 cubic feet per second rate when the eruption began Sunday night, similar to the high rates of the 2018 eruption.

“It’s been chugging along,” Dietterich said.

>> PHOTOS: Scientists continue to monitor Kilauea activity

The crater, which has a capacity of 2.22 billion cubic feet, was 25% filled as of midday Wednesday with 565 million cubic feet of lava, said Dietterich, who is on loan to the USGS Hawaiian Volcanoes Observatory from the Alaska Volcano Observatory staff.

However, there’s no need for concern if Halemaumau spills over like an unattended bathtub.

Instead, lava would spill onto the caldera floor.

Kilauea caldera is a “series of nested pits,” the geophysicist described, and Halemaumau crater is “a deep hole within other holes.”

The entire 2018 summit collapse area is 29.4 billion cubic feet, so to fill that would take 240 days at the current rate.

The effusion rate, or the volume of lava over time, is a more accurate portrayal of what is happening than the rise of the lava lake since Halemaumau is a deep pit with steep sides and a funnel shape.

The lava lake’s rise was faster initially since the bottom of the crater is like the narrower part of a funnel.

As of Wednesday morning, it had risen 75 feet in 24 hours.

The lake’s surface, measured at 8 a.m. Wednesday, was 1,522 feet below the crater rim observation site, compared with 1,598 feet at 5 a.m. Tuesday.

By 2 p.m. Wednesday, the lava lake’s rise slowed to 60 feet in 24 hours.

Interestingly, a 500-foot island of cooler, solidified lava inside the lake has been shrinking and drifting eastward through Wednesday morning since Tuesday.

“We don’t have a prediction on how long it lasts,” Dietterich said. “It can be on the order of a couple weeks.”

A couple of weeks was the average duration of an eruption in the 1920s and 1930s, she added.

Because Kilauea had a 35-year run of continuous eruption activity until the 2018 eruption ended after four months of lava flow in Puna, scientists “haven’t studied it when it wasn’t in a state of eruption,” she said.

“We don’t want to hazard a guess,” she said. “If the eruption rate is sustained at this level, we can expect it to keep going.”

On Wednesday, lava continued to pour into the lake from two fissure vents.

The west vent is from a higher point on the wall of the crater, flowing down the wall, resembling a waterfall.

The larger north vent is in the process of being drowned, meaning the lava is rising above the vent, so it’s unknown what the effect might be, Dietterich said.

As vents get covered, it’s harder to see what’s happening, but lava could still flow in from beneath the surface level, Dietterich said.

“Post-2018, it’s been repressurizing,” she said. “We had water at the surface. It was a little bit surprising. We’re still understanding it and monitoring it.

In 1959, the Kilauea Iki eruption was on the side of the Kilauea Iki pit crater. When the crater filled with lava up to the level of the vent, there were pauses in eruption and lava would drain back into the vents, she said.

Hawai‘i Volcanoes National Park warned visitors Wednesday that the Kilauea summit was blanketed in high levels of sulfur dioxide and particulates, considered hazardous by the Environmental Protection Agency.

The park staff put up signs warning visitors of the conditions, and issued alerts on social media sites.

Visitors are urged to check the air quality website at www.HawaiiSO2Network.com before coming to the park.

“When air quality is poor, visitors should get in their vehicles, turn on the air conditioner, and go to another area not impacted by volcanic gas,” said the park Superintendent Rhonda Loh. “There are no safe options for visitors to seek shelter indoors in the park due to the pandemic.”