Achmad Ibrahim / AP
Indonesian volcano slowing but not finished yet
By SLAMET RIYADI
MOUNT MERAPI, Indonesia — Hot ash poured more slowly from an Indonesian volcano Friday, but experts warned that Mount Merapi could still erupt again as villagers reported that even rare leopards living near the crater have begun to evacuate.
In a reminder of the volcano's deadly power, the National Disaster Management Agency raised the death toll from a series of eruptions to 206 on Friday. That figure continues to edge upward as officials count those who have died from respiratory problems, heart attacks and other illnesses related to the blasts.
Mount Merapi began unleashing torrents of hot gas, rock and other debris more than two weeks ago after years of dormancy. The most significant blast came last Friday, the deadliest day at the mountain in decades.
The volcano is the most volatile in Indonesia, a vast archipelago of 235 million people that prone to d seismic activity because it sits along the Pacific "Ring of Fire," a horseshoe-shaped string of faults that lines the Pacific Ocean.
Ash has continuously shot out of the crater since it roared to life Oct. 26, occasionally canceling international flights into and out of Jakarta, hundreds of miles (kilometers) to the volcano's west. After the output slowed overnight, an advisory from the Volcanic Ash Advisory Center in Darwin, Australia, showed the ash patch was well clear of the capital. The airport in Yogyakarta, at the foot of the mountain, however, remained closed.
Officials warned residents that less ash does not mean the volcano is finished.
"The activity of Merapi is still high, but the intensity of eruptions is reducing now. But people still should be careful. Merapi is still on high alert," said Surano, a state volcanologist who uses only one name.
While officials struggle to persuade hundreds of thousands of people who live on the volcano's fertile slopes not to return to their homes, a new kind of evacuee has been sighted in recent days. Villagers checking on their homes and crops have seen leopards — who live in a national park near the crater — heading down the mountain.
"I was shocked and afraid that they will pounce on me ... so I ran as fast as possible," said Ahmad Sokidi, whose house is six miles (10 kilometers) from the summit.
The cats likely feel the continuing tremors, said Tri Prasetyo, who runs the park, and are seeking safer ground. It's also possible that prey is scarce in areas scorched by searing gases.
The Javan leopard — a subspecies of the cat only found on the island of Java — is critically endangered, with no more than 250 left in the wild. Some put the total population as low as 50.
While the total cost of the volcano disaster has not been tallied yet, officials have already estimated that tens of millions of dollars in crops, forest and fish farms have been lost. Garuda Indonesia, the country's flag carrier, said it has lost 2.5 billion rupiah ($280,000) each day since the airport at Yogyakarta closed last Friday.
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How Icelandic volcano issued warnings months before its eruption
• Volcanologists document events before it blew
• Eyjafjallajökull had one swollen flank for 11 weeks
- guardian.co.uk, Wednesday 17 November 2010 20.05 GMT
Furore borealis: the northern lights illuminate the plume of ash above Eyjafjallajökull on the evening of 22 April, the day the volcano re-erupted after a pause lasting two days. Photograph: Lucas Jackson/Reuters
It left the skies over Britain clear of aircraft trails for the first time in decades and led to travel misery. For several days in April, flights in northern Europe were grounded as a cloud of ash and dust spewed out of the Eyjafjallajökull volcano in Iceland and were blown around the continent.
Now, the geological events leading up to the eruption have been documented, and they show that the volcano had been rumbling for many months before it blew its top. In a paper published today in Nature, Freysteinn Sigmundsson, of the Nordic Volcanological Centre at the University of Iceland, describes how he led an international team to use a combination of GPS, seismic monitoring and satellite radar interferometry to track years of deformations and volcanic activity on and around Eyjafjallajökull.
Sigmundsson found that for 11 weeks before the volcano began erupting in March, one flank was swollen by more than 15cm (6in). Magma had been flowing from deep underground into shallower compartments under the mountain.
Kurt Feigl, a professor of geosciences at the University of Wisconsin-Madison and a co-author of the study, said the volcano had been showing signs of restlessness. "Several months of unrest preceded the eruptions, with magma moving around downstairs in the plumbing and making noise in the form of earthquakes," he said. "By monitoring volcanoes, we can understand the processes that drive them to erupt."
The deformation of the Earth's crust around Eyjafjallajökull, and the resulting small earthquakes, began to increase in January. A few weeks later, sensors and GPS stations began detecting rapid expansion of the mountain.
The first eruption, caused by magma flowing into the mountain from underneath, began on 20 March. It continued for three weeks before pausing for two days and then resuming on 22 April.
The second time around, the erupting lava punched through the ice at the top of the mountain. The water exploded into steam and rapidly cooled the magma, which is a mixture of molten rock and various solid impurities, and normally circulates under the Earth's crust. The magma turned into a fine-grained dust cloud that rose high into the atmosphere and was blown around the whole of northern Europe. Sustained, highly variable activity continued until 22 May, with an average of 30,000-60,000 litres (6,600-13,200 gallons) of magma coming out every second.
Normally, when volcanoes erupt, they deflate as the magma drains out. But for some reason, Eyjafjallajökull kept its shape after the first eruption.
The researchers suggested that this could be because of a limited supply of magma in the first place, and the position of the volcano. The volcanoes of Iceland are the surface peaks of the Mid-Atlantic Ridge, but Eyjafjallajökull lies at some distance from the main rift zone. This means less heat from magma reaches it than reaches volcanoes nearer the rift zone.
The eruption was probably started by an intrusion of magma deep inside the volcano, though this is something that needs to be confirmed at other volcanoes.
The researchers stress that study of the events leading up to the eruption will not necessarily help to predict future events. "We're still trying to figure out what wakes up a volcano," said Feigl.
"The explosiveness of the eruption depends on the type of magma, and the type of magma depends on the depth of its source. We're a long way from being able to predict eruptions. But if we can visualise the magma as it moves upward inside the volcano, then we will improve our understanding of the processes driving volcanic activity."
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