Volcano of Mud in Indonesia was Caused by Humans and Not an Earthquake

First Posted: Jun 30, 2015 09:01 AM EDT

The mud volcano disaster in Indonesia may actually have been caused by humans. Scientists have taken a closer look at the Lusi mud flow and have found that it may have had its roots in human interference.

In May 2006, a mud volcano opened up in the city of Sidoarjo in East Java, Indonesia. Nine years later, the eruption continues; in fact, it's buried more than 6.5 square kilometers of the city in up to 40 meters of mud and has displaced almost 40,000 people. Costs of the disaster are estimated to be over $2.7 billion.

"There has been intense debate over the cause of the mud volcano ever since it erupted," said Mark Tingay, lead author of the new study, in a news release. "Some researchers argue that the volcano was human-made and resulted from a drilling accident (a blowout) in a nearby gas well. Others have argued that it was a natural event that was remotely triggered by a large earthquake that occurred 250 kilometers away and two days previously. There has been no scientific consensus about this and it's a very hot topic politically in Indonesia."

In this latest study, the researchers used physical data collected in the days before and after the earthquake rather than using models and comparisons. In the earthquake-trigger theory, researchers proposed that seismic shaking induced liquefaction of a clay layer at the disaster location. This was associated with extensive gas release that then helped mud flow upwards and erupt on the surface.

The data, though, shows that no gas release followed the earthquake. Not only that, but rocks showed no response to the earthquake, which means that an earthquake couldn't have been responsible for the mud flow disaster. In contrast, measurements that highlight the onset of underground activity preceding the mud eruption only started when a drilling "kick" occurred.

"We demonstrate that erupting fluids were initially sourced from a deep formation, which is only predicted to occur in the drilling-trigger hypothesis," said Tingay. "Taken together, our data strongly supports a human-made trigger. We hope this closes the debate on whether an earthquake caused this unique disaster."

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