Volcanoes are usually stately and sometimes violent. Great mountains with smooth slopes and circular calderas, they lie dormant for centuries, or give off occasional wisps of steam and, more rarely, surges of lava and clouds of ash. And every now and then, one of them explodes spectacularly.
But the volcano that erupted at 5am on 29 May 2006 in Porong, Indonesia, was different; no mountain, just a spreading lake of simmering mud and a 30m plume of sulphurous steam. Up to 50,000 people lost their homes, more than a dozen villages were submerged and two dozen factories abandoned. Rice paddies and shrimp ponds were inundated, roads and railways diverted. The death toll so far is 13, killed when a gas pipeline ruptured.
At its peak, the mud volcano, called Lusi, pumps out 150,000 cubic metres a day, enough to fill Wembley Stadium in about three weeks. And it’s been gushing for nearly two and a half years, with no end in sight.
One recent study by a Durham University-led team considered what Lusi would be like if it keeps erupting for another decade. Attempts to cork the volcano by dropping thousands of concrete balls linked by chains into the vent failed completely. Environmentalists fear that diversion of the mudflow into the Porong river will destroy the local fisheries. Meanwhile the levees keep rising.
Mud volcanoes are not well understood, partly because they usually occur on the seabed. What is clear is that a hot, high pressure reservoir of liquid, in this case mostly water, broke through a rocky cap and began percolating through a layer of clay, turning it into mud and carrying it up to geyser forth at the surface.
The cause of this disaster has generated scientific, legal and political debates as heated as the 60C eruption. Two hypotheses are in play, one is that the magnitude 6.3 Yogyakarta earthquake, which killed 6,000 people two days earlier and 260km away, triggered Lusi. The other is that the Banjar Panji-1 drilling rig operated by PT Lapindo Brantas, which was exploring for natural gas just 150 metres from Lusi’s main vent, set it off.
The legal and political arguments swirl around this central scientific issue. Legally the question is who should pay for dealing with the disaster and compensating the victims. If the drilling was at fault, the companies involved should cough up. If it was a consequence of the earthquake, the government is responsible. The stakes are high; the IMF estimates the cost of Lusi at some £2bn.
And that’s where the politics comes in. Lapindo is 50 per cent owned by Energi Mega Persada, part of the business conglomerate controlled by the family of Aburizal Bakrie, Indonesia’s Co-ordinating Minister for the People’s Welfare. Mr Bakrie has been criticised for distancing himself from the disaster, both as a businessman and as a minister. His refusal to visit Lusi prompted angry activists to spray 700kg of mud on his ministry’s gates in Jakarta. Although his family’s company provides food and other aid to the refugees, and has agreed to pay them £240m in compensation, they denounce it at every turn.
The scientific question came to the fore again at the Geological Society of London on 22 October. Proponents of the earthquake hypothesis, employed by the oil companies, claimed that evidence from their well proved its innocence.
Bambang Istadi, a geologist and exploration manager at Energi Mega Persada, argued that if the 2,800m borehole was guilty, a powerful pressure spike, called a kick, would have been observed. Although there was a spike, he said the roughnecks brought it under control in less than an hour, before it could damage the rock formation. Pressure tests since then have shown that the well is intact; with no leaks in or out. Nor is there any evidence of an underground blowout in the formation surrounding the well; if there had been, the borehole’s temperature would have risen to match the volcano’s and the remaining piece of the drill left in the hole would have slipped down into an opening abyss. So if it wasn’t the well, it must have been the earthquake.
Professor Richard Davies of Durham University’s Centre for Research into Earth Energy Systems, who also made a presentation to the Geological Society, remained unconvinced. The kick was powerful enough to damage the rock formation, he argued, and the lower portion of the well had not been sheathed to prevent such problems. The evidence cited by Mr Istadi can be explained if the massive upheaval when the volcano was triggered resulted in the well becoming pressure sealed from what was going on around it. And crucially, the earthquake was too far away and too weak to have caused the mud volcano. So if it wasn’t the earthquake, it must have been the drilling.
The scientific question, then, is far from settled. But progress is being made. So confident are they of their data, that Mr Istadi and the companies have agreed to share it with Professor Davies. If one side or the other can carry the scientific argument, the legal and political issues will be clarified too. For the people whose homes have been swallowed by Lusi, that can only be good.