A new analysis shows that a deadly mud volcano in Indonesia may not have been a natural disaster after all. The research lends weight to the controversial theory that the volcano was caused by humans.

Villagers near Sidoarjo noticed a mud volcano beginning to erupt at 5 a.m. local time May 29, 2006. It was about 500 feet from a local gas-exploration well. Every day since then, the Lusi mud volcano has pumped out 100,000 tons of mud, or enough to fill 60 Olympic-size swimming pools. It has now covered an area of almost 3 square miles to a depth of 65 feet. Thirty thousand people have been displaced, and scientific evidence is mounting that the company drilling the well caused the volcano.

"The disaster was caused by pulling the drill string and drill bit out of the hole while the hole was unstable," said Richard Davies, director of the Durham Energy Institute and co-author of a new paper in the journal Marine and Petroleum Geology, in a press release. "This triggered a very large 'kick' in the well, where there is a large influx of water and gas from surrounding rock formations that could not be controlled."

Mud volcanoes can form in two different ways. New fractures in rock that caps mud deposits can open, allowing the mud to rise to the surface if it's under pressure. Or, an earthquake can liquefy mud that then travels through pre-existing cracks to the surface.

Davies argues that the "kick" fractured the rock in the area, opening up new pathways for pressurized mud to come flowing up to the surface. Davies' team's research uncovered new evidence from a drilling log that the drilling company, Lapindo Brantas, pumped drilling mud down their well to try to stop the mud volcano.

"This was partially successful, and the eruption of the mud volcano slowed down," Davies said. "The fact that the eruption slowed provides the first conclusive evidence that the bore hole was connected to the volcano at the time of eruption."

The new paper came in response to a paper published by the company's lead driller in the same journal. Lapindo Brantas has long maintained that drilling did not cause the eruption. Instead, the company claims an earthquake that occurred two days before and about 175 miles away did the damage. Obviously, there are financial ramifications if the drilling company is found liable for the disaster.

The problem with the earthquake hypothesis is the stress changes caused by the quake would have been relatively small, too small to cause the volcano, said Davies' co-author, University of California at Berkeley geologist Michael Manga.

"There is 1,000 times not enough energy to cause the eruption," Manga said.

He was drawn into the controversy when the drilling company cited one of his papers on how earthquakes can cause mud volcanoes and have on 32 occasions. But Manga noted that based on all the historical examples that scientists have, what the company claimed happened was impossible.

"So I wrote a one-page paper [in 2007] saying it could not possibly have caused the mud volcano," he said.

Other scientists came to similar conclusions, although some doubts remained.

An even stronger piece of evidence that the earthquake could not have created the mud volcano, Manga said, is that in the years before the quake, there were "bigger and closer earthquakes that did not cause an eruption."

In fact, the stress changes associated with the tides are larger than the stresses caused by the earthquake that happened to strike two days before the mud volcano eruption began.

Still, the editor of the journal in which both the company's paper and the Manga-Davies rebuttal was published said that it was possible that the same data could be subject to multiple interpretations.

"In geology, sometimes it's not about being right or wrong, it's about being reasonable or unreasonable," said editor Octavian Catuneanu, geologist at the University of Alberta. "The funny thing is that sometimes datasets can be interpreted by different people in different ways, and this leads to arguments and controversies."

Still, there is a large financial incentive for Lapindo Barantas' scientists to find that their company was not responsible. "The drilling company cannot say anything different, right?" Manga said.

But Catuneanu said that no matter who the scientists were working for, they still had to meet the scientific standards of the journal.

"I guess there would be some bias there, but as a journal editor, what I need to make sure is that the authors of an article stick to the science," he said. "If they want to have something publishable, they have to bring data and discuss it in a scientific manner."

Lapindo Barantas could not be reached for comment.

Images: 1. AP Photo/Trisnadi

2. NASA

See Also:

WiSci 2.0: Alexis Madrigal's Twitter, Tumblr, and green tech history research site; Wired Science on Twitter and Facebook.