The world's supervolcanoes: An eruption is a matter of time<\/p>\n
After the tsunami disaster there has been further evidence of
\nearthquake activity around Sumatra. Australia's volcanologist Ray
\nCas, a professor of the Department of Earth Science, Monash
\nUniversity Melbourne, recently spoke to The Jakarta Post's
\ncontributor Dewi Anggraeni about volcanoes and earthquakes.<\/p>\n
Question: Can you explain the situation with the
\nsupervolcanoes or calderas. Are there any indications of an
\nimminent eruption?<\/p>\n
Answer: I have been misquoted in the press who had me saying
\nthat the next supervolcano eruption would be in Lake Toba,
\nSumatra. There are around 100 supervolcanoes or calderas around
\nthe world. These have not erupted in the historic times, and
\ntherefore it is a matter of time before one does erupt.<\/p>\n
I drew analogy with the tsunami disaster on Dec. 26, saying
\nthat, the tsunami was an event that was going to happen somewhere
\nand sometime, and of course unfortunately it occurred in the
\nregion of Indonesia which was highly populated, and had the
\ndisastrous effect.<\/p>\n
If a supervolcano erupts, the consequences could be two to
\nthree times worse, simply because of the enormity of the
\neruptions that result from the supervolcanos. Supervolcanoes have
\nthe capacity to erupt up to 1,000 cubic kilometers of molten
\nlava, distributed around the landscape as ash and rock debris,
\nand can cause enormous devastation up to 200 kilometers away from
\nthe erupting volcano.<\/p>\n
Are there any supervolcanoes in the region surrounding us?<\/p>\n
Indeed the biggest supervolcano in the world is Lake Toba,
\nwhich last erupted 73,000 years ago, and that eruption actually
\nhad a significant effect on global climate. At the time the
\nglobal climate was deciding whether to return to the ice age or
\ncontinue the warming process. Volcanologists and climatologists
\nagree that, that eruption was enough to swing it back to the ice
\nage. The release into the atmosphere of huge volumes of fine ash
\nparticles and thousands of tons of a gas called sulphadioxide
\nwhich combined with water droplets in the atmosphere, blocked out
\nthe incoming solar radiation.<\/p>\n
And if a supervolcano erupts, and that supervolcano is in
\nclose proximity to the oceans, the eruptions usually produce very
\nlarge-volume flows of gas and rock debris, which we call
\npyroclastic flows. These are capable of flowing in speeds of tens
\nto hundreds of kilometers per hour for distances of up to 200
\nkilometers from the volcano.<\/p>\n
What is the likelihood of the earthquake activity around
\nSumatra triggering the eruption of the Lake Toba supervolcano?<\/p>\n
Some scientists do think that some eruptions of these
\nsupervolcanoes can be triggered by large scales of regional
\nearthquakes, of the sort that has been experienced around Sumatra
\nin the last few months.<\/p>\n
In other words, there will have to be very large volumes of
\nmolten rocks or magma in the below-the-ground surface, below the
\nvolcano. And we will normally see evidence of this, if that is
\nthe case. We'll see increased rates of gas release from gas
\nfumeroles, and the opening of new gas fumeroles.<\/p>\n
At present, there is no evidence that, that condition exists
\nat Lake Toba. But there is no question that in the future some
\ntime, the Toba supervolcano could erupt again. However there is
\nno evidence at the moment that it will happen in the foreseeable
\nfuture.<\/p>\n
What are the normal cycles of supervolcanic eruptions?<\/p>\n
Supervolcanoes erupt very rarely. Take Lake Toba which last
\nerupted 73,000 years ago. Before then it was 790,000 ago. So some
\ncycles are tens of years, some hundreds of years. In relation to
\nLake Toba, because the last eruption was 73,000 years ago, we
\nstill consider that Lake Toba is a potentially active volcano.<\/p>\n
What can be learned from the tsunami disaster?<\/p>\n
The lesson to be learned is that had there been adequate
\nmonitoring facilities, and warning systems in place, at least the
\nloss of lives would have been very significantly reduced. The
\nsame principle applies to understanding and anticipating the
\neruptions of volcanoes with potential destructions and hazards.<\/p>\n
So the message is, if at all possible we should increase the
\ndegree to which we monitor volcanoes, and to help us better
\nunderstand future possible eruptions.<\/p>\n
How do you see the recent earthquake in Padang, and subsequent
\nearthquakes nearby in the context of the wider volcanic activity
\nin the region?<\/p>\n
To the west, along Sumatra island there is what is called the
\nJava Trench or the Sunda Trench. This represents a location where
\na large segment of the Indian Ocean lithospheric plate is being
\nrecycled. And it is the recycling of the lithospheric plate and
\nthe overlaying plate, the Asian plate, that causes the large
\nearthquakes that have been experienced in the region.<\/p>\n
However that trench lies offshore in the ocean and to the
\nwest of the island. In the meantime, onland in Sumatra there is a
\nfaultline called the Sumatra faultline. Lake Toba is located
\nalong part of this faultline. But the Sumatra faultline is not
\njust a single faultline. There are a number of subsidiary or
\nsplinter faults, which branch off the main faultline. It is
\npossible that the Padang earthquake you mentioned was related to
\nsubsidiaries of the Sumatra faultline.<\/p>\n
You don't hear alarm bells from the Lake Toba supervolcano?<\/p>\n
At this stage not. One immediate potential risk could be if
\nthere was a fault in Lake Toba, if there is movement on the floor
\nof the lake, that could generate some tsunamis in the lake.<\/p>\n
How do we know if that happens?<\/p>\n
Once an earthquake occurs, seismologists can actually
\ncalculate where the earthquake occurred. If it is immediately
\nunderneath Lake Toba, then it is likely there has been movement
\nof the crust. The question is whether the movement is sideways or
\nthere is a vertical component. If there is a vertical component,
\nit will almost certainly trigger tsunamis within the lake.<\/p>",
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