Scientists explain world's largest mud eruption

"Lusi's not going to stop anytime soon," geoscientist Stephen Miller said.
By Brooks Hays  |  Oct. 17, 2017 at 2:25 PM
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Oct. 17 (UPI) -- Scientists now know why boiling hot mud continues flow from vents on the Indonesian island of Java.

Researchers detailed their explanation for the "most destructive ongoing mud eruption in history" in a new paper published in the Journal of Geophysical Research: Solid Earth.

In 2006, a combination of mud, water, rocks and gas began to spill from a number of newly formed vents on Java. The hot mud flows threatened villages and rice fields, forcing evacuations and requiring the construction of levees. Dubbed Lusi, the eruption is ongoing.

Eleven years after it began, Lusi vents continue to spill 3 million cubic feet of mud every day. Occasionally, the vents expel geyser-like plumes of gas and rock debris.

Now, thanks to new imaging technology, scientists have a better understanding of the unique underground volcanic plumbing responsible for the ongoing mud flows.

Images of Lusi roots show the vents and mud flows are linked through a system of faults with the magma chamber of the nearby Arjuno-Welirang volcanic complex.

Over time, the volcanic system's magma has been baking the earth beneath the Lusi vents. The process, which produces an excess of gas, has built up a tremendous amount of pressure beneath Lusi. An earthquake in 2006 offered the opportunity for Lusi to release this pressure.

"We clearly show the evidence that the two systems are connected at depth," Adriano Mazzini, a geoscientist at the University of Oslo, said in a news release. "What our new study shows is that the whole system was already existing there -- everything was charged and ready to be triggered."

Mazzini and his colleagues used a series of seismometers installed two years ago to image the contours of the sediment and rocks beneath Lusi. Their observations revealed a tunnel stretching from Lusi to the magma chamber beneath Arjuno-Welirang. The tunnel allows magma and hydrothermal fluids to flow from the mantle and mix with sediment beneath Lusi, building up pockets of highly-pressurized gas over time.

"It's just a matter of reactivating or opening these faults and whatever overpressure you have gathered in the subsurface will inevitably want to escape and come to the surface, and you have a manifestation on the surface, and that is Lusi," Mazzini said.

Java is part of a chain of islands formed by volcanoes, and the movement of magma beneath Lusi may represent the migration of the volcanic arc northward.

"It looks like this might be the initial stages of this march forward of this volcanic arc," said Stephen Miller, a professor of geodynamics at the University of Neuchâtel in Switzerland. "Ultimately, it's bringing all this heat over toward Lusi, which is driving that continuous system."

While mud flows are fairly common on Java, Lusi is a unique hybrid -- the combination of a mud volcano and hydrothermal vent. Unlike other mud volcanoes, Lusi has a more massive thermal engine in the form of a large magma chamber.

"So what it means to me is that Lusi's not going to stop anytime soon," Miller said.

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