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You are here: BBC > Science & Nature > TV & Radio Follow-up > Horizon

Volcano Hell
First shown: BBC Two, Thursday 17 January 2002

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Nevado del Ruiz eruption in video It began with a ghastly tragedy. In 1985 the massive Colombian volcano Nevado del Ruiz erupted, melting a glacier and sending a vast landslide of mud down on the people asleep in the town of Armero below. Twenty thousand died.
Nevado del Ruiz eruption in videoRun video

In the aftermath science was set a challenge: to make sure such a catastrophe never happened again, by finding a way of accurately predicting when a volcano will erupt. Now, at last, it seems that one scientist may have met that challenge.

B-type vibrations in video

Prediction to the day

Anyone can tell when a volcano becomes active. You can see it and you can smell it. But a volcano can be active for years without erupting. For those living nearby, there is no way they will abandon their homes and livelihoods just because of a few rumblings. The only way to persuade them to seek safety is to predict an eruption almost to the day, leaving just enough time for an evacuation.
B-type vibrations in videoRun video

Scientists threw themselves at the problem, but there just seemed to be no way to make sense of the violent forces at work inside a volcano. Then along came Bernard Chouet. He is different from other volcanologists. His training lay in the complex equations and theories of physics, and he believed the answer had to lie in analysing the mysterious patterns drawn by seismographs. These measure the tremors caused by active volcanoes.

Bernard Chouet explains long period events

Good vibrations

Previous attempts to use these tremors to predict eruptions had proved fruitless. No one could find any correlation between the squiggles on the graph paper and the timing of eruptions. So Chouet locked himself away for five years and then emerged claiming he had found the answer. The key, he said, were seismic signals called long period events. These strange shapes had baffled volcanologists for years.
Bernard Chouet explains long period eventsRun video

Bernard Chouet explains resonance Chouet said they were made by molten magma resonating - that is coming under pressure - inside the volcano. The more long period events there were, then the nearer the volcano was to exploding. Chouet could use the long period events to predict an eruption to within days.
Bernard Chouet explains resonanceRun video

Larry Malconico on Mount Etna in video

Sniffing gas

But another scientist was working on a completely different method. Stanley Williams could not be more different from Chouet. Where Chouet crunched numbers and looked at graphs, Williams climbed into craters and got up close; because he believed the best clue to when a volcano would erupt was to measure how much gas it was belching out.
Larry Malconico on Mount Etna in videoRun video

In 1993 the two methods came head to head. A conference was held at the foot of another Colombian volcano, Galeras. The highlight was to be a trip into the crater. Williams's gas readings indicated the volcano was safe. Chouet's long period events suggested the volcano might blow. After some debate, Williams led a team of volcanologists up the mountain. Suddenly Galeras exploded, killing six scientists and three tourists. Williams himself survived but was maimed for life.

Eruption of Popocatepetl in video

Saving lives

Since that day on Galeras, Chouet's methods have commanded wide respect and have been increasingly used around the world. In a dramatic demonstration last year Mexican scientists used Chouet's method to predict an eruption of the mighty volcano Popocatépetl. Tens of thousands of people were safely evacuated just before the biggest eruption of the volcano for a thousand years. No one was hurt.
Eruption of Popocatepetl in videoRun video

Find out more

Surviving Galeras
Stanley Williams, 2001. Little, Brown & Co., London.

No Apparent Danger
Victoria Bruce, 2001. HarperCollins Publishers, New York.

BBC Horizon - Supervolcanoes
www.bbc.co.uk/science/horizon/1999/supervolcanoes.shtml

BBC Science - Hot Topics: Natural Disasters
www.bbc.co.uk/science/hottopics/naturaldisasters/volcanoes.shtml

BBC News - Popocatépetl eruption, December 2000
http://news.bbc.co.uk/hi/english/world/americas/newsid_1077000/1077476.stm

Volcano Live
www.volcanolive.com/contents.html

Volcano World
http://volcano.und.nodak.edu/vw.html

Smithsonian Institute - Global Volcanism Programme
www.volcano.si.edu/gvp/

US Geological Survey - Volcano Hazards Programme
http://volcanoes.usgs.gov/

International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI)
www.iavcei.org/

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