What to do when your Volcano bubbles but won’t go off?


Lessons for Bali from Mount Pinatubo 1991

Just nine hours prior to writing this, on 29 October, news came that the Volcano Alert for Bali’s Mt. Agung had been lowered from Level 4, in effect since 22 September, to Level 3; indicating that the danger of an eruption at any moment had been lowered from crtitical to serious. Authorities reduced the Exclusion Zone from 12 km to 6 km, allowing large numbers of the almost 140,000 evacuated Balinese villagers to return to their homes.

Not before time it seems, as Level 4 had been in effect for 38 days and nothing had happened and already some 4,000 farmers and villagers had  quit the 390 odd camps scattered across the island. Unfairly, if understandably, feeling they had been misled and their lives disrupted because the mountain had failed to erupt.

That’s the thing about volcanoes – you can never tell exactly when, if and how they will go off. Some with a great big bang like Mt. St. Helen’s blowing itself in half in 1980, others with a slow oozeof lava over decades like Big Island, Hawaii. Volcanoes are by no means the most lethal of natural disasters, largely because they don’t move and, unlike their deadlier cousins, earthquakes and tsunamis, today you get plenty of warning if things are hotting up. That’s why volcanoes kill far fewer than other major natural disasters. But, in the wrong combination that could change. When a volcano erupts explosively and, if that eruption blows the side off the mountain instead of the top, and – if a pyroclastic tsunami of toxic gas and volcanic material travelling over half the speed of sound envelops a densely populated city, say. Think Mt Rainier exploding horizontally in a North Easterly direction like Mt St. Helens, one of the most cataclysmic detonations in modern history but with a death toll of just 57, and what would that do to the Seattle/Tacoma area do you reckon?

In 1902 Mt Pelee in Martinique, an island one fifth the size of Bali, erupted explosively wiping out the capital St. Pierre killing 30,000 people or 15% of the population. More recently in 1985 the killer Mt. Nevada del Ruiz in Columbia blew for the fourth time in modern history destroying the town of Armero nested below and killing 23,000 of its citizens.

Perhaps the most important lessons for Bali may be learned from the eruption of Mt. Pinatubo on Luzon Island in the Philippines in 1991, when the second largest volcanic eruption of the last 100 years, and by far the largest explosion to affect a densely populated area, occurred. The eruption  produced high-speed avalanches of hot-ash and gas, giant mudflows and a cloud of volcanic ash hundreds of miles across. The effects of which continue to this day.

The point for Bali is that, cataclysmic as this explosion was, the death toll of 847 was relatively modest. It could easily have been in the tens of thousands. The reason for this being advances in modern vulcanology were applied and heeded, the local population was evacuated and most pertinent of all, that the mountain blew up on cue. If it hadn’t, as indeed we see here in Bali, you can’t expect to remove people from their homes and livelihoods for very long and nothing happens. They don’t stand for it. It’s a dilemma we’re going to need to face.

Following a major earthquake in the region in 1990 Mt. Pinatubo had shown signs of increasing of activity, but otherwise appeared to be continuing its 500-year slumber. In March and April 1991 magma rising to the surface from more than 30 km beneath the mountain triggered small earthquakes and caused powerful steam explosions blasting three craters in side of the volcano. Thousands of small earthquakes were logged beneath Pinatubo through April, May and June and thousands of tons of toxic sulfur dioxide were emitted.  By mid-June the first magma reached the surface and millions of cubic tons of gas-charged magma exploded spectacularly. Two days later more magma reached Pinatubo’s suface and the volcano exploded in a cataclysmic eruption spewing more than 5 cubic kilometres into the atmosphere (picture that covering the entire state of Rhode Island  2 metres deep with concrete). The ash cloud rose 35 km into the air. At lower altitudes the entire region was covered in a blanket of volcanic ash of sand, glass and volcanic mineral. Fine ash fell as far way as the Indian Ocean and the ash cloud circled the world several times.

Most lethal were huge avalanches of searing hot ash, gas and pumice that sped down the mountain at enormous speed filling valleys and burying villages. The eruption emiited so much magma and rock from below the volcano that the summit collapsed to form a large depression or caldera 2.5 km accross.

Following the eruption thousands of roofs collapsed under the weight of ash made wet by heavy rains. Ash deposits from the eruption created by the monsoon rains became giant mud flows(lahars) that covered fields and villages to caused more destruction than the eruption itself.

It was fortunate that scientists from the Filipino vulcanologists and the US Geological Survey could forecast the eruption saving thousands of lives – but the eruptions changed the face of central Luzon, home to about 3 million people. 200,000 evacuees from the more distant lowland areas subsequently returned to their homes and within five years the villages, rice paddies and sugar-cane fields not buried by lahars had recovered. Large covered areas will remain useless for many years to come. Some 20,000 highlanders living close to the volcano were completely displaced and remained in settlement camps for up to a decade.

Indonesia and Bali appear to be doing a good job monitoring and taking the necessary action to prevent risk of a large death toll. The question remains, what do you do if the Bali’s holy mountain chooses not to play ball and does not go off when it should, but waits until all the displaced people lose patience and go home – and then the balloon goes up?

I guess if things don’t just settle down for another 50 years we have to hope for a small non-explosive eruption that goes upward and not landward and without the destructive pyroclastic flows and ensuing lahars.

As for tourism not being affected in an island the size of Bali? Dream on.  Remember how not so long ago aviation in Europe came to a virtual stand still for inside of a month because of a not so very explosive volcanic eruption in Iceland with nary a life lost,  but an economic cost of billions?

One last sobering thought. Dramatic as they are volcanic eruptions are the least lethal of all natural disasters. Mainly because you know one may be on its way and most volcanoes are not in densely populated areas. No, nature’s No.1 killers and economic destroyer are earthquakes and tsunamis and no one’s yet found the way to predict them. Unfortunately we’re  slap bang just a few 100 kilometres from a major tectonic fault and  I’ve yet to hear of ‘Tsunami Tourism’. It’s hard to see what more the authorities can do but pray and plan for an aftermath.  As for the rest of us we might give a thought to our nearest high places.

Mt.PinatuboAlternative Voice

ParacelsusAsia

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