Geological forces inside the earth unleash disaster

Early on Monday 29 May 2006, a mud volcano started erupting in East Java, Indonesia, near the village of Sidoarjo.1 Boiling water, steam, gas and mud began gushing from the ground just 200 metres (650 feet) from a drilling well exploring for natural gas.

Enough mud is flowing out of the volcano to fill 50 Olympic swimming pools every day.2 The mud has destroyed factories, schools, 10,000 homes, a dozen villages and displaced over 50,000 people. It has buried a major freeway and a railway line.3

Some say it was caused by a “kickback” at the tip of the drill that fractured the rock strata around 2,000 m below the surface. Others say it was caused by an earthquake that hit the coast of Central Java two days before (see box).






Earthen walls have been built and now contain the mud to an area of seven square kilometres (3 sq. miles). The mud is up to 20 metres deep.

The locals call the volcano Lusi.4 Every effort to stop the eruption has failed, including dams, drainage channels and even dropping massive concrete balls into the crater. Scientists think the volcano will continue erupting for decades. More homes are threatened as new mudflows appear in the vicinity.

In 2007, geologists reported that the land around the mud volcano was subsiding. The mud escaping from beneath the surface was allowing the overlying rock strata to collapse. It could be the start of a caldera—a large basin-shaped volcanic depression. So far the ground under the mud has subsided over 60 m and the volcano has risen more than 25 m.5 Some geologists believe that, as the land subsides, more cracks could open up that develop into new mud volcanoes, making the mud volcano self-perpetuating.1

Even though the Lusi mud volcano has been disastrous for the local area, the total volume of mud extruded in the first few years was less than one tenth of a cubic kilometre (0.1 km3). That is small compared with volcanos such as Mt St Helens in the USA which ejected one cubic kilometre (1 km3) of material in its 1980 eruption.6 In 1883, the infamous Indonesian volcano, Krakatoa, blasted out 18 km3 of material.7 Even larger still, the Taupo volcano in New Zealand ejected an enormous 800 km3 of debris, creating a huge caldera (now Lake Taupo, the largest freshwater lake in Oceania) a few thousand years ago.8….

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