VOLCANO, Hawai'i — Scientists have learned a lot since Kīlauea Volcano began erupting 10,001 days ago.

But they admit having little idea what the next 10,000 days will bring for the world's longest continuously erupting volcano.

"It couldn't be more interesting," said Jim Kauahikaua, scientist-in-charge at the U.S. Geological Survey's Hawaiian Volcano Observatory. "There's something about this eruption that you find in very few eruptions: we can study it up close every day."

The eruption, which yesterday marked its 10,000th consecutive day of activity, has been a major attraction for scientists and tourists since the volcano's east rift zone vent known as Pu'u 'Ō'ō turned active on Jan. 3, 1983.

A summit vent on Halema'uma'u Crater has been erupting since March 19, 2008. That vent opened when the crater wall collapsed and now belches sulfur dioxide gas and ash while flinging rocks as big as coffee tables more than 1,300 feet into the air.

Eight explosive events were recorded later that year as the vent expanded to more than 400 feet in diameter. A large lava pond bubbles some 600 feet down the vent.

"That is a very deep pit," geologist Tim Orr said. "We've come to a much better understanding of lava dynamics by watching the lava pond."

Mike Poland, observatory geophysicist, said he and his colleagues learn more every day by tracking the movement of the underground lava known as magma.

"Volcanoes tell you when they are restless," he said. "We're not bad at predicting, but what we need to work on is when it's going to stop. We have no idea."

The science team works closely with park rangers whose main job is keeping some 2 million visitors safe each year.

One four-mile stretch of a road that circles Halema'uma'u Crater is closed to visitors because of dangers posed by sulfur dioxide in the gas that constantly spews from the vent.

A daily average of nearly 900 tons of volcanic gas — known locally as vog — typically drifts out to sea. But when the wind shifts, it blows across agricultural land and town centers. High levels of vog have been blamed for failed crops and respiratory distress in residents.

There are 130 miles of marked trails in the 333,000-acre park, with 15 miles closed due to the volcano.

"We want visitors to be able to experience the park's wonders and we don't like to close areas off," park Superintendent Cindy Orlando said. "But we have to be aware of the changing conditions."