Scientists Unearth Revealing Details about the World’s Biggest Mud Volcano

By Annie Sneed

In May 2006 boiling mud, gas, water and rock started gushing out of the ground in northeastern Java, one of the islands in the Indonesian archipelago. The massive mud volcano—nicknamed “Lusi”—has continued to spew its hot contents even today, more than 11 years later. Experts say Lusi is the largest mud volcano in the world, now covering seven square kilometers of land. Since 2006 Lusi has dislocated some 60,000 people and caused more than $4 billion in economic damages.

Mud volcanoes are not actual volcanoes—their temperatures are much cooler, and they erupt a mix of rock, clay and mud rather than lava. Some say Lusi is a combination of these two systems, although others debate this. In fact, Lusi remains a mystery to scientists in many ways. One of the biggest and most contentious questions about Lusi concerns what triggered the eruptions: an earthquake or natural gas drilling? Now, in a new study, researchers have imaged the subsurface plumbing system of Lusi. Their work reveals that—regardless of what triggered the eruption—Lusi likely connects at deep depths to a nearby volcanic system.

Several studies had already analyzed the geochemistry of the materials bursting from Lusi. They showed its innards had a volcanic origin, says Adriano Mazzini, a geoscientist at the Center for Earth Evolution and Dynamics at the University of Oslo in Norway. “We could already infer that somehow Lusi and a neighboring volcanic complex are connected at depth,” he says. “What we were missing was a real image of the subsurface that could visually prove this connection between the two.” For the new study, published in October in the Journal of Geophysical Research: Solid Earth, Mazzini and his team installed a large network of seismometers in three areas: Lusi; the volcanic system; and a tectonic fault zone spanning the two. The group then collected 10 months of data from the seismometers and used that information to piece together a picture of the subsurface across these locations.

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