VOLCANO, Hawai'i — The summit of Kilauea volcano is glowing brightly as molten lava swirls 300 feet below its crater's floor.

The expanding vent of Halema'uma'u crater helps confirm scientists' belief that the lava is close to the Earth's surface, said Janet Babb, a geologist and spokeswoman for the U.S. Geological Survey's Hawaiian Volcano Observatory.

"We can actually catch glimpses and confirm early speculation that there's lava not too far down," Babb said.

Kilauea has been erupting for more than 25 years, with its lava creating a plume of steam as it spills into the Pacific Ocean.

But this recent activity is coming from the top of the volcano, not its sea-level side.

Scientists don't know if lava will ever erupt in a fountain from within the crater, Babb said.

"There's no way to know if that will ever materialize," she said. "It would be grand to see some fountaining here."

The changes in the crater have not created any increased risk to visitors or park staff, she said.

Park rangers are keeping the overlook at the Jaggar Museum open later at night to accommodate the growing number of visitors arriving at dusk or after dark to view the glow.

Volcanic smog — known as vog — is emitted regularly from the crater, spreading a haze of toxic sulfur dioxide over the island. Sometimes the haze is thick enough to cause illnesses, kill crops and force school closures.

A non-lava eruption from the summit in March 2008 rained gravel-sized rocks onto a lookout, road and trail, forcing parts of the park to close.

Measurements taken this week showed that sulfur dioxide emissions remain similar to recent elevated levels, Babb said.

This is the strongest glow coming from the crater since October.

The unpredictable nature of volcanos means scientists will have to wait to see what comes next, Babb said.

"We've certainly seen glowing vents before," she said. "There were several in the floor of the Pu'u 'O'o (vent). It wasn't as deep. It certainly bore a resemblance to what we're seeing in Halema'uma'u today."