Posted on April 17 2018
Not too terribly far beneath our feet, the Earth is a very different place from the pleasant zone we live in. The deepest mines, which can reach down to depths of a mere two and a half miles, are very hot jobsites. Just another handful of miles deeper (depending upon your location) puts you at the outermost zone of the mantle, from whence magma can flow, bursting forth from the conduits we know as volcanoes. Hot lava—it’s what volcanoes do. But there’s another kind of volcano that brings forth another kind of material from below the surface—mud. For all the drama that a spewing volcano evokes, the thought of mud burbling up from the depths just seems so boring and uninteresting. However, a particular mud volcano in Indonesia has drawn a lot of interest because it has made quite a large, dangerous nuisance of itself.
Not unlike the Paricutín volcano that unexpectedly rose up out of a cornfield in Mexico one day, the mud volcano named Lusi on the Indonesian island of Java popped out of a rice paddy in May of 2006. The name Lusi is made up from the first parts of “lumpur”—Indonesian for “mud”—and Sidoarjo, the name of the local area. It started pouring forth two days after a magnitude 6.3 earthquake rocked Yogjakarta, a city about 150 miles from the Sidoarjo area. The earthquake seemed like a logical trigger for such an event, but another possible cause raised a controversy. Only 650 feet from the eruption site, drilling for natural gas was underway, and some blamed that for the arrival of the mud. And there has been plenty of reason for people to want to assign blame. Since 2006, Lusi’s mud has covered about six square miles. Villages have been buried, some as deep as 130 feet, 13 people have been killed, and 60,000 people have had to flee their homes. Property loss has run into the billions of dollars. And Lusi continues to erupt.
Those who pin the responsibility for the disaster on the drilling posit a scenario wherein an impermeable layer of rock 9,300 feet under the surface capped a permeable layer that held an aquifer. When the drilling broke through the overlying layer, the pressure of the water burst upward, carrying mud with it. As mud came back up the borehole, possibly as a result of inadequate casing, workers capped the well to prevent a blowout. But the pressure in the hole may have acted as a sort of natural fracking action, shattering rock deep in the Earth, resulting in the surface eruption close by the drilling rig. The drilling company has been reluctant to disclose well pressure data that might support the argument for this explanation, but the wealthy owners of the company have nevertheless been forced by the government to pony up funds to mitigate the losses of the local people.
More recently, researchers have found reasons to believe that the drillers are not at fault, and that nature may be the cause of the disaster after all. Mud volcanoes usually result from the violent expulsion of built-up methane and carbon dioxide gases. Studies of gases emanating from Lusi indicate that they indeed have a magmatic source. Seismic testing in the area has determined that there is a magma chamber in a nearby volcanic system that extends a hydrothermal vent into the sediment under Lusi. This particular plumbing doesn’t entirely exonerate the gas drillers, because even though all of it was already in place, the action that set off the mud volcano might have been either the earthquake, or the pressure release caused by drilling through the capping rock layer.
Whatever the cause, the expulsion of hundreds of millions of cubic yards of mud has meant that the surface of the whole area has subsided substantially. Early in the eruption the land dropped by about an inch and a half a day, but it has since slowed to a few inches a year. However, Lusi has been projected to continue to spew for anywhere from 20 to 87 years, so the land may drop a good deal more. As a practical matter, something had to be done with the continuously arriving mud, given that repeated attempts to plug the volcano have all met with failure. Earthen berms have been built to contain the flowing material and then pump it to a nearby river where it now feeds the formation of an island of more than 200 acres, and a growing delta. It is an imperfect solution, as the mud has buried all the animal and plant life on the river’s bottom, and the volatile chemicals it carries pollute the water and plague the lungs of the local people.
Lusi is not a unique feature—mud volcanoes are not unusual, especially around subduction zones where water-rich sedimentary layers are pushed deep into the Earth and volcanic zones develop. Java has a number of other examples. But Lusi is a standout for its size and longevity, and especially its negative effect on a human population. Some scientists expect more of them could develop in Lusi’s neighborhood, so understanding their operating mechanisms and future behaviors is important to planning the best way to live with the challenges they present.
Yes, there is mud volcano tourism on Java! If that doesn’t thrill you, check out some other more visually delightful island landforms in Lonely Planet’s guide to Indonesia. Maps.com has it available at the click of a mouse, right here:
caption: NASA satellite false-color image of Lusi mud volcano taken in 2009. The reds are actually fields of green crops; whitish areas are water. The linear shape shows the barriers built to contain the spreading mud, and where the mud has flowed to the nearby river.
source: Wikimedia Commons: NASA (Public domain)