HILO, Hawai'i — Small splatters of molten lava were ejected from the new vent at Halema'uma'u Crater Sunday night, marking the first time lava has erupted from anywhere at the crater since 1982.

Some particles were ejected with enough force to land on the rim of the crater, with the largest fragments of splatter or blobs of molten rock measuring about four inches across.

The gas at Halema'uma'u is now thick with ash, causing the plume from the 100-foot-wide vent to look dusty brown.

The eruption of lava wasn't wholly unexpected given the huge recent increase in gas emissions from the vent, and the lava splatter doesn't necessarily signal that a large-scale crater eruption is about to begin, said Jim Kauahikaua, scientist-in-charge at the U.S. Geological Survey's Hawaiian Volcano Observatory.

All of the other large-scale eruptions at the summit have been preceded by increases in earthquakes and inflation or ground swelling at the summit, and that hasn't happened yet, he said. Under the circumstances, a large-scale eruption at the crater in the near term "is not likely, but it's certainly a possibility," Kauahikaua said.

Scientists continue to monitor the volcano closely because there may not be a great deal of warning that a summit eruption is coming.

"Some of these events are only preceded by hours to days worth of really unusual behavior," Kauahikaua said. "Usually the inflation is a lot longer-scale than that, but the earthquakes can be hours to days in advance."

Visitor traffic at Hawai'i Volcanoes National Park remained busy despite the closures last week of Crater Rim Drive from Kilauea Military Camp to Jaggar Museum, and the closure of the museum because of the risk of explosions and gas emissions, said park Ranger Mardie Lane.

"People are here and our parking lots are full, and there may be some level of frustration over current closures, but the view of the ash-laden plume blasting out of Halema'uma'u more than makes up for it," Lane said.

Observers looking over the crater at about 7:15 p.m. Sunday saw red-hot fragments scattering from the vents, and yesterday morning geologists reported finding the thin strands of volcanic glass known as "Pele's hair" along with the small bits of volcanic glass known as "Pele's tears" in the crater overlook area.

Pele's hair and tears signify that fresh lava is present at the vent along with gas.

"There's still not a lot of lava," Kauahikaua said. "You could probably put the whole thing in the back of a pickup truck, all the stuff that we found, and have a lot of room left over," he said.

The volume of sulphur dioxide gas released at the summit was about 1,300 metric tons per day as of Sunday, which is about 10 times the normal summit emissions. Meanwhile, the emissions at the Pu'u 'O'o vent have held steady, meaning Kilauea overall is now producing about double its normal volume of sulphur dioxide.

With the addition of ash to the plume rising out of the summit vent, aviation agencies have been warned that the airborne ash may present a risk to tour flights and other aircraft in the area, scientists said.

Ian Gregor, spokesman for the Federal Aviation Administration, said the agency released a notice late last week warning pilots not to fly below 1,000 feet in the area because of sulphur dioxide.

The volcanic ash is not yet rising high enough to prompt the FAA to warn commercial airlines about the emissions or to reroute air traffic, he said.

If the ash and fumes are lifted higher, "we could fairly quickly implement a flight restriction around the area that would keep all air traffic out of there for safety reasons," but the FAA has no immediate plans to do so, Gregor said.

Previous eruptions at the crater included lava that flowed into the crater from fissure eruptions on its southwest rim in 1974 and 1971, and an eight-month eruption in Halema'uma'u in 1967 and 1968 that created a lake of lava that covered the entire crater floor.