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Monday, 06 November 2017 01:00

Scientists determine source of world’s largest mud eruption (video)

Scientists determine source of world’s largest mud eruption (video) Credits: ABC.com

More than 11 years after the Lusi mud volcano first erupted on the Indonesian island of Java, researchers have probably figured out why the mudflows haven't stopped: deep underground, Lusi is connected to a nearby volcanic system.

On May 29, 2006, what seemed to be a mud volcano erupted in an urban area of the Indonesian island of Java. Boiling mud, water, rocks and gas poured from open vents in the ground, burying entire towns and forcing many Indonesians to evacuate. By September 2006, the eruption site reached a peak, with the mud being gushed on the surface able to fill 72 Olympic-sized swimming pools daily.

The eruption, known as Lusi, is still ongoing and has become the most destructive ongoing mud eruption in history. The sea of mud has buried some villages 40 meters deep and forced nearly 60,000 people away from their homes. Indonesians frantically built levees to contain the mud and save the surrounding settlements from being covered. Nowadays, the volcano is oozing around 80,000 cubic meters of mud each day - enough to fill 32 Olympic-sized pools.

The island of Java is part of a volcanic island arc, formed when one tectonic plate subducts below another. As the island rose upward out of the sea, volcanoes formed along its spine, with basins of shallow water between them. Lusi's mud comes from sediments laid down in those basins while the island was still partially submerged underwater.

In a new study, researchers claim to have determined why Lusi's mudflows are still ongoing today. Two years ago, the study's authors installed a network of 31 seismometers around Lusi and the neighboring volcanic complex. Researchers typically use seismometers to measure ground shaking during earthquakes, but scientists can also use them to create three-dimensional images of the areas underneath volcanoes.

Using 10 months of data recorded by the seismometers, the researchers imaged the area below Lusi and the surrounding volcanoes. The images show that the conduit supplying mud to Lusi is connected to the magma chambers of the nearby Arjuno-Welirang volcanic complex through a system of faults 6 km below the surface. This allows magma and hydrothermal fluids originating in the mantle to intrude into Lusi's sediments, which triggers massive reactions and creates gas that generates high pressure below Earth's surface. Any perturbation - like an earthquake - can then trigger this system to erupt.

"We clearly show the evidence that the two systems are connected at depth," said Adriano Mazzini, a geoscientist at CEED - University of Oslo and lead author of the new study in the Journal of Geophysical Research: Solid Earth, a journal of the American Geophysical Union. "What our new study shows is that the whole system was already existing there - everything was charged and ready to be triggered."

Mazzini and other researchers suspect a magnitude 6.3 earthquake that struck Java two days before the mud started flowing on May 2006 was what triggered the Lusi eruption, by reactivating the fault system that connects it to Arjuno-Welirang. They are unsure, however, how much longer Lusi will continue to erupt. While mud volcanoes are fairly common on Java, Lusi is a hybrid between a mud volcano and a hydrothermal vent, and its connection to the nearby volcano will keep sediments cooking for years to come.

A video on the Lusi mud eruption is available below.

Source: American Geophysical Union

Read 48 times Last modified on Monday, 06 November 2017 14:28

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American Geophysical Union (AGU)

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