The three-year-old eruption of Lusi, as it has become known, in Sidoarjo, East Java, pumps out about 100,000 cubic meters of scalding mud a day, said Mark Tingay, a lecturer in applied geology at Perth's Curtin University of Technology. That's enough to fill more than 50 Olympic-sized swimming pools, he said. Flows started at about 5,000 cubic meters a day and peaked at 170,000 cubic meters.

"This is really only an estimate," Tingay said in a Geological Society of Australia statement. "The high flow rate may only continue for two or three years, or it might continue for hundreds of years."

The mud started flowing in May 2006 after a blowout in the Banjar Panji well drilled by Lapindo Brantas Inc. in a venture with Santos Ltd., Australia's third-biggest oil and gas producer. Santos bought out of the venture last year to limit its involvement in any possible damage claims from the incident.

While the boiling mudflow has been contained within about 7 square kilometers (2.8 square miles), about 100,000 people remain at risk from subsidence of the surrounding land, said Tingay, who is studying the incident with scientists from Indonesia, the U.K. and the U.S. The mud volcano is about 690 kilometers (431 miles) east of Jakarta.

Land is sinking between 2 and 5 centimeters (2 inches) a day under the weight of as much as 30 meters of mud, he said in an Earth Science Showcase report. At times, land has slumped as much as 3 meters in 12 hours.

Best Option

With no sign of the flow abating, pumping the non-toxic mud into the Porong River remains the best option, he said. The river empties into the sea.

After the incident, well-operator Lapindo blamed an earthquake two days earlier in the Yogyakarta region in central Java for triggering the mudflow. Partner PT Medco Energi Internasional accused Lapindo of not casing the well properly.

While the Yogyakarta tremor was likely too small to have caused the mudflow, there are also conflicting views on whether a drilling accident could have triggered it, Tingay said.

"The trigger for Lusi may never be conclusively proven either way," he said.