Sounding out Natures's fury
At first, I think it’s snowing. But when the flakes leave a dirty white mark on my sleeve, I’m not so sure. ‘It’s ash,’ confirms Nick Varley, professor of volcanology at Colima University, Mexico. ‘Those rumbles we’ve been hearing can’t have been thunder after all. They must have been eruptions. You’d better put your helmet on.’
We’re standing in a thin pine forest on a steep rocky slope 800 metres below the crater of Volcán de Colima in southwestern Mexico, one of the world’s most hazardous volcanoes. Not only are we on the remains of an old lava flow, but we’re surrounded by boulders the size of small cars that have been spat out of the crater. So I’m not sure how much use my plastic climbing helmet will be. But neither Varley, a Brit who has been working in Mexico for more than ten years, nor his American colleague Jeff Johnson appear too worried. So I feign indifference and concentrate on the scene in front of me.
Varley and Johnson are moving bags of earth and a pile of old branches from the top of a large grey plastic crate buried snugly in a pit. Removing the lid reveals several car batteries and an assortment of plastic boxes. What look like ordinary hi-fi leads connect the boxes to one another. The whole lot seems to be held together with electrical tape. This is what I’ve endured two nights’ camping at freezing temperatures, a breathless, seven-hour hike and several bouts of vertigo to see. Hi-tech this is not. And if I didn’t know better, I would be disappointed.
But this apparent school-boy set-up is Johnson’s brainchild, representing one of the most significant and sophisticated developments in volcano monitoring in recent years. Its installation at Colima could make a significant contribution towards the science of eruption prediction and could help to avert future humanitarian disasters.
Due for a big one
Volcán de Colima, or Fuego as it’s locally known, stands 3,860 metres high in the western portion of the Mexican Volcanic Belt. It’s the youngest of three volcanoes that form the Colima Volcanic Complex. Viewed from the south, it’s a perfect brown cone that towers majestically over a peaceful subtropical idyll. Farmers corral their cattle on horseback in meadows speckled with wildflowers. And residents of sleepy colonial towns enjoy long lunches and promenades around the plaza.
I first met Varley two days earlier in his dusty office at Colima University. Surrounded by climbing equipment, ancient PC modules and bags of grey volcanic ash, he explained why experts believe Colima is primed for a massive explosion. ‘The volcano has been erupting continuously, albeit fairly gently, since 1998,’ he said. ‘And history shows that a large, paroxysmal explosion occurs every 100 years or so, after ten or 15 years of such low-level activity.’
The last time it erupted on this scale, in 1913, it belched a column of ash more than 20 kilometres into the atmosphere. Super-hot pyroclastic flows raced more than 15 kilometres across the surrounding countryside, incinerating everything in their path. Pointing to a colour-coded hazard map on the wall, Varley explained that a similar event today would threaten the lives of more than 15,000 people in nearby towns and villages and the property of another 400,000 in the cities of Colima and Guzmán. ‘But the next eruption could be ten times as powerful,’ he said, ‘as big as the eruption of Vesuvius, which destroyed Pompeii in 79 AD.’
Research shows that Colima has an even more violent past. There’s evidence to suggest that during its 5,000-year history, Colima has experienced a ‘sector collapse’, when a significant proportion of the volcanic edifice itself gives way during an explosive eruption, creating huge avalanches. ‘This is the worst possible scenario and would devastate a much larger area, including the entire city of Colima,’ says Gabriel Reyes Davila, director of the university’s volcano observatory. ‘We’re not expecting anything like this in the near future, but with volcanoes, you can never be 100 per cent certain about anything.’
Given Colima’s history of activity, the state of Colima authorities have gone to great lengths to educate the local population about evacuation procedures. Leaflets distributed to every household explain that in the event of an eruption, buses will be commandeered and sent to pick up the residents from the plazas of towns and villages in the danger zone. Melchor Ursuna Quiroz, director of the state’s civil defence team, tells me proudly that during simulations, more than 19,000 people have been evacuated in less than two hours.
However, carrying out an effective evacuation is the easy part. Working out when to do it is considerably more difficult. ‘We evacuated the local area in 2006 when we were convinced that an explosion was imminent,’ says Quiroz. ‘But in the event, nothing serious happened, and the people who were staying in emergency shelters grew frustrated and began asking to go back.’
There’s no doubt that ordering evacuations is an extremely delicate business. In 1999, thousands of evacuees from the town of Baños in Ecuador rioted when the government refused to allow them to return to their homes after a predicted eruption of Tungurahua failed to materialise. ‘It’s a stressful decision to have to make,’ says Quiroz. ‘People’s lives and livelihoods are at stake. So we need to have the most accurate information possible.’
But, as Reyes points out, accuracy is extremely difficult to achieve when trying to predict a volcanic eruption. ‘Remember the St Helens eruption [in Washington state in 1980]? Everyone was expecting a vertical explosion, but it ended up being lateral one. Nature is like a woman,’ he says with a wink. ‘You can never be sure how she is going to react.’
Box of tricks
Back on the flanks of Colima, the ash is swirling in the breeze. Pulling out his Leatherman tool to tinker with a circuit board, Johnson explains that predicting the timing and size of an explosive eruption remains difficult because measurements made with the volcanologist’s traditional instruments leave many questions unanswered. ‘A seismograph is the volcanologist’s principal tool and is used for the detection of tremors caused by the movement of magma, rock fractures or an explosion,’ he says. ‘But it can’t always distinguish between them, and in many cases gives little indication of an eruption size.’
This is where Johnson’s box of tricks can help. It contains an infrasound recording station, consisting of an infrasound sensor and a telemetry system, itself comprising a digitiser and modem. A few yards away, an antenna transmits information to the university. Two solar panels charge the car batteries off which the instruments feed.
First developed for the detection of nuclear weapons testing, infrasound sensors work on the same principle as a microphone, but record at frequencies of less than 20 Hertz – the range in which elephants and whales communicate, and way below what is audible to humans. When it comes to volcanoes, infrasound sensors enable a far more accurate interpretation of signals from eruptions, says Johnson. ‘The beauty of infrasound is that events such gas emissions, landslides or the movement of magma display characteristic waveforms by which we can tell them apart and, crucially, assess their magnitude.’
This station is the third of four being deployed at Colima. ‘Four is the magic number for infrasound,’ says Johnson. ‘It enables us to pinpoint activity with more accuracy.’ The final installation was partially carried out in December last year, with the infrasound being installed in temporary fashion. The more permanent installation with seismometer was postponed until later this year. ‘The fourth station is about 200 metres below the crater rim, which is about as close as we can get without actually being up there,’ says Varley.
Although this isn’t the first time infrasound technology has been used in volcanology, it’s the first permanent installation deployed at such close range to a hazardous volcano. As such, says Johnson, it’s far more sensitive than long-range systems. ‘This infrasound network will provide the opportunity to improve our understanding of the processes that cause an eruption, not only at Colima but at hundreds of other similar stratovolcanoes around the world.’
The beauty of Johnson’s stations is that they’re relatively inexpensive – a few thousand US dollars each. ‘You can spend US$10,000 or more on a top-of-the-range infrasound sensor,’ he says. ‘But if you get in close enough, you really don’t need to spend that kind of money. I make all of my sensors in the lab, and they only cost a couple of hundred dollars each.’
This means that networks of Johnson’s infrasound sensors could improve volcano monitoring in parts of the developing world, particularly in Latin America and the Pacific, where funds are scarce. Nevertheless, Johnson is modest about his ambitions. ‘I hope that the information collected at Colima will enable those at observatories and in government who have to make the really tough decisions – that affect peoples’ lives and livelihoods – to do so with more confidence.’
May 2009
We’re standing in a thin pine forest on a steep rocky slope 800 metres below the crater of Volcán de Colima in southwestern Mexico, one of the world’s most hazardous volcanoes. Not only are we on the remains of an old lava flow, but we’re surrounded by boulders the size of small cars that have been spat out of the crater. So I’m not sure how much use my plastic climbing helmet will be. But neither Varley, a Brit who has been working in Mexico for more than ten years, nor his American colleague Jeff Johnson appear too worried. So I feign indifference and concentrate on the scene in front of me.
Varley and Johnson are moving bags of earth and a pile of old branches from the top of a large grey plastic crate buried snugly in a pit. Removing the lid reveals several car batteries and an assortment of plastic boxes. What look like ordinary hi-fi leads connect the boxes to one another. The whole lot seems to be held together with electrical tape. This is what I’ve endured two nights’ camping at freezing temperatures, a breathless, seven-hour hike and several bouts of vertigo to see. Hi-tech this is not. And if I didn’t know better, I would be disappointed.
But this apparent school-boy set-up is Johnson’s brainchild, representing one of the most significant and sophisticated developments in volcano monitoring in recent years. Its installation at Colima could make a significant contribution towards the science of eruption prediction and could help to avert future humanitarian disasters.
Due for a big one
Volcán de Colima, or Fuego as it’s locally known, stands 3,860 metres high in the western portion of the Mexican Volcanic Belt. It’s the youngest of three volcanoes that form the Colima Volcanic Complex. Viewed from the south, it’s a perfect brown cone that towers majestically over a peaceful subtropical idyll. Farmers corral their cattle on horseback in meadows speckled with wildflowers. And residents of sleepy colonial towns enjoy long lunches and promenades around the plaza.
I first met Varley two days earlier in his dusty office at Colima University. Surrounded by climbing equipment, ancient PC modules and bags of grey volcanic ash, he explained why experts believe Colima is primed for a massive explosion. ‘The volcano has been erupting continuously, albeit fairly gently, since 1998,’ he said. ‘And history shows that a large, paroxysmal explosion occurs every 100 years or so, after ten or 15 years of such low-level activity.’
The last time it erupted on this scale, in 1913, it belched a column of ash more than 20 kilometres into the atmosphere. Super-hot pyroclastic flows raced more than 15 kilometres across the surrounding countryside, incinerating everything in their path. Pointing to a colour-coded hazard map on the wall, Varley explained that a similar event today would threaten the lives of more than 15,000 people in nearby towns and villages and the property of another 400,000 in the cities of Colima and Guzmán. ‘But the next eruption could be ten times as powerful,’ he said, ‘as big as the eruption of Vesuvius, which destroyed Pompeii in 79 AD.’
Research shows that Colima has an even more violent past. There’s evidence to suggest that during its 5,000-year history, Colima has experienced a ‘sector collapse’, when a significant proportion of the volcanic edifice itself gives way during an explosive eruption, creating huge avalanches. ‘This is the worst possible scenario and would devastate a much larger area, including the entire city of Colima,’ says Gabriel Reyes Davila, director of the university’s volcano observatory. ‘We’re not expecting anything like this in the near future, but with volcanoes, you can never be 100 per cent certain about anything.’
Given Colima’s history of activity, the state of Colima authorities have gone to great lengths to educate the local population about evacuation procedures. Leaflets distributed to every household explain that in the event of an eruption, buses will be commandeered and sent to pick up the residents from the plazas of towns and villages in the danger zone. Melchor Ursuna Quiroz, director of the state’s civil defence team, tells me proudly that during simulations, more than 19,000 people have been evacuated in less than two hours.
However, carrying out an effective evacuation is the easy part. Working out when to do it is considerably more difficult. ‘We evacuated the local area in 2006 when we were convinced that an explosion was imminent,’ says Quiroz. ‘But in the event, nothing serious happened, and the people who were staying in emergency shelters grew frustrated and began asking to go back.’
There’s no doubt that ordering evacuations is an extremely delicate business. In 1999, thousands of evacuees from the town of Baños in Ecuador rioted when the government refused to allow them to return to their homes after a predicted eruption of Tungurahua failed to materialise. ‘It’s a stressful decision to have to make,’ says Quiroz. ‘People’s lives and livelihoods are at stake. So we need to have the most accurate information possible.’
But, as Reyes points out, accuracy is extremely difficult to achieve when trying to predict a volcanic eruption. ‘Remember the St Helens eruption [in Washington state in 1980]? Everyone was expecting a vertical explosion, but it ended up being lateral one. Nature is like a woman,’ he says with a wink. ‘You can never be sure how she is going to react.’
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Box of tricks
Back on the flanks of Colima, the ash is swirling in the breeze. Pulling out his Leatherman tool to tinker with a circuit board, Johnson explains that predicting the timing and size of an explosive eruption remains difficult because measurements made with the volcanologist’s traditional instruments leave many questions unanswered. ‘A seismograph is the volcanologist’s principal tool and is used for the detection of tremors caused by the movement of magma, rock fractures or an explosion,’ he says. ‘But it can’t always distinguish between them, and in many cases gives little indication of an eruption size.’
This is where Johnson’s box of tricks can help. It contains an infrasound recording station, consisting of an infrasound sensor and a telemetry system, itself comprising a digitiser and modem. A few yards away, an antenna transmits information to the university. Two solar panels charge the car batteries off which the instruments feed.
First developed for the detection of nuclear weapons testing, infrasound sensors work on the same principle as a microphone, but record at frequencies of less than 20 Hertz – the range in which elephants and whales communicate, and way below what is audible to humans. When it comes to volcanoes, infrasound sensors enable a far more accurate interpretation of signals from eruptions, says Johnson. ‘The beauty of infrasound is that events such gas emissions, landslides or the movement of magma display characteristic waveforms by which we can tell them apart and, crucially, assess their magnitude.’
This station is the third of four being deployed at Colima. ‘Four is the magic number for infrasound,’ says Johnson. ‘It enables us to pinpoint activity with more accuracy.’ The final installation was partially carried out in December last year, with the infrasound being installed in temporary fashion. The more permanent installation with seismometer was postponed until later this year. ‘The fourth station is about 200 metres below the crater rim, which is about as close as we can get without actually being up there,’ says Varley.
Although this isn’t the first time infrasound technology has been used in volcanology, it’s the first permanent installation deployed at such close range to a hazardous volcano. As such, says Johnson, it’s far more sensitive than long-range systems. ‘This infrasound network will provide the opportunity to improve our understanding of the processes that cause an eruption, not only at Colima but at hundreds of other similar stratovolcanoes around the world.’
The beauty of Johnson’s stations is that they’re relatively inexpensive – a few thousand US dollars each. ‘You can spend US$10,000 or more on a top-of-the-range infrasound sensor,’ he says. ‘But if you get in close enough, you really don’t need to spend that kind of money. I make all of my sensors in the lab, and they only cost a couple of hundred dollars each.’
This means that networks of Johnson’s infrasound sensors could improve volcano monitoring in parts of the developing world, particularly in Latin America and the Pacific, where funds are scarce. Nevertheless, Johnson is modest about his ambitions. ‘I hope that the information collected at Colima will enable those at observatories and in government who have to make the really tough decisions – that affect peoples’ lives and livelihoods – to do so with more confidence.’
May 2009
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