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Volcanoes: Unpredictable, Dangerous and Fascinating

Aired July 27, 2001 - 22:14   ET

THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.


THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.
BILL HEMMER, CNN ANCHOR: Now our special report this evening: when the earth spits and volcanoes erupt, they can be fascinating and furious. And they can also be dangerous. The images from Italy's Mount Etna have been captivating us all week, and tonight, still angry, Europe's largest active volcano has emergency crews scrambling now to prevent further disaster. CNN's Matthew Chance is there.

(BEGIN VIDEOTAPE)

MATTHEW CHANCE, CNN CORRESPONDENT (voice-over): The turbulent slopes of Mount Etna, Europe's biggest active volcano, still bursting with molten rock and choking gas. Thick layers of black ash are again blanketing towns and villages around its slopes, and still no clear sign of when this powerful eruption will ease.

Driving through the blackened passes that climb Mount Etna, we traveled toward the heart of the volcanic zone, 2,500 meters, nearly 8,000 feet, above sea level. Volcanologists here, experts in these eruptions, have a living laboratory in the clouds.

These scientific tools are casting light on Mount Etna's unpredictable eruption and on the levels of harmful gases, like carbon dioxide, that have been spewing from the volcano for days. But scientists say these poisonous emissions make little impact on the global environment.

And it is humans who stand to lose the most at the edge of this lava flow. Scientists had hoped the worst was over, but here there is little evidence of that.

(on camera): These intensive eruptions and the really staggering flows of lava have in the past few days been confounding the predictions of many scientists. And much of the local wisdom here along Mount Etna is that it's only this smoldering mountain itself that really knows what it will do next.

Matthew Chance, CNN, on the slopes of Mount Etna.

(END VIDEOTAPE)

HEMMER: That is in Southern Europe.

In the Philippines at this time, another volcano is smoldering with experts warning it could blow its top again at any time. The Mayon volcano let out three huge blasts on Thursday, sending ash clouds miles into the air and spitting out rocks the size of cars. Thousands nearby fled their homes, and today many returned to help clean up.

So, why is it then that volcanic eruptions are so hard to predict, and what causes the Earth's crust to open up anyway? CNN science correspondent Ann Kellan with a few answers about the science behind volcanoes.

(BEGIN VIDEOTAPE)

ANN KELLAN, CNN SCIENCE CORRESPONDENT: When will a volcano like Mount Etna blow?

UNIDENTIFIED MALE: Is this a dome itself here?

UNIDENTIFIED MALE: Yes, this is lava (UNINTELLIGIBLE).

KELLAN: That's what brings scientists to the center of active volcanoes, like this group inside Mount St. Helen. Tilt meters measure surface movements. Crack meters measure fissures in the mountain wall. Seismic sensors monitor for earthquakes. Thermal and infrared sensors on board satellites look for hot spots. All this helps volcanologists get better at predicting when, but not enough to be precise.

TERRY KEITH, U.S. GEOLOGICAL SURVEY: We can get to the order of days to hours very well. But if we don't have those instruments in -- and, as I said, a lot of volcanoes don't have instruments -- there will be surprise eruptions.

KELLAN: All those measurements taken inside and above the mountain are trying to gauge the pressure building up inside the mountain. Volcanoes typically form where the earth's tectonic plates collide, an area of intense heat, which melts water and rock together into a super-hot slime, called magma. That magma slowly rises through veins in the middle of a mountain.

As it gets close to the surface, that pressure builds. In some cases, magma violently explodes out the top of the mountain, like Mayon in the Philippines, still erupting now. This more explosive type of volcano typically takes longer to build, like Mount St. Helen's, which blows every 100 years.

In other volcanoes, like Etna, magma bursts through cracks in the mountain.

KEITH: Etna is a volcano that does not have these big explosive eruptions that send ash way up into the atmosphere and the stratosphere.

KELLAN: Less forceful, more spectacular. And, like Etna, usually much more frequent.

KEITH: Etna's erupted every couple of years for the last 10,000 years. And it's almost always got some visible activity going on. KELLAN: Magma at the surface is called lava. Still scalding, as hot as 3,000 degrees.

But most people who die from volcanoes don't die from the lava flow, but suffocate from inhaling the thick ash, or drown in mud flows. As challenging as the science is, scientists say the hardest part of their job is deciding when to recommend evacuations. Evacuate too early, and people might return before it erupts. Evacuate too late, and people can't escape the mud flows or choking ash.

Ann Kellan, CNN, Atlanta.

(END VIDEOTAPE)

HEMMER: Something else you may not know about volcanoes, they can dramatically change the climate for years to come. With more on that, meteorologist Karen Maginnis tracking that this evening.

Karen, good evening.

KAREN MAGINNIS, CNN METEOROLOGIST: Hey, Bill. Yes, we've got a fairly spectacular picture of what's going on with Etna. Here it is. You can see that long plume of ash and smoke and debris -- tephra is the name that is applied to the debris that is in the air. Can be of any size, but usually the heavier objects fall out of the sky after about the first -- usually within the first couple of weeks, but it can take as much as four months.

All right, we've got some spectacular climate changes that have occurred as a result of the volcano and climate relationship. Mount St. Helen's, which you probably just heard about, lowered the global temperature just a smidgen, bit we had even more spectacular volcanoes that did that.

Iceland's Laki, it produced a severely cold winter in the Eastern United States, also throughout much of Europe. They were saying there were snows and frost even in June, July and August. And then, there is Krakatoa, very famous, 1883, killed 36,000 people and it caused unusual sunsets. They are saying in London it was especially spectacular there. Also, very cool weather throughout much of the year. It lowered the temperature about five degrees Celsius, Bill, so this can actually travel around the world multiples of times, and really can have dramatic changes as far as the climate is concerned.

HEMMER: Curious to know, Karen, how long can those changes last?

MAGINNIS: Well, initially, there's usually about a four-month window where we start to see the initial -- actually, it's a warm-up, because you get large particles in the atmosphere. Then, when that becomes a little more hazy, you get the haze and that actually blocks the sun out, so you see that cooling effect, and this can take place over a year to two years, usually two years is about the average.

HEMMER: Interesting stuff. Karen Maginnis, thanks, have had a great weekend, OK, Karen.

MAGINNIS: You too. All right.

HEMMER: See you on Monday.

For a lot more information on volcanoes, head to CNN.com and click on the "volcano" section there. A lot more stuff on the mountains of fire, including a very cool, as you see, a cool animation that we'll show you how they work -- again, at CNN.com.

They're mother nature's temper tantrum: treacherous, unpredictable, destructive. Our fascination with volcanoes continues just ahead here on CNN TONIGHT.

(COMMERCIAL BREAK)

HEMMER: And we finish our special report tonight with an unconventional look at the world's relationship with volcanoes, held together with equal parts fear and fascination. For more, here's CNN's Thomas Nybo.

(BEGIN VIDEOTAPE)

THOMAS NYBO, CNN CORRESPONDENT (voice-over): As long as nobody gets hurt, the world loves a good volcano. There's something about hot lava that latches onto the imagination and doesn't let up. It looks like something you'd want to touch, maybe toss around the backyard like a baseball.

But that would be as ridiculous as, I don't know, petting a shark.

UNIDENTIFIED FEMALE: Harry, are you an idiot or what?

NYBO: Few things in nature have the raw power of a volcano. A river of lava is like an 800-pound gorilla, only this gorilla is on fire and really, really angry. Lava is stubborn and cute like a baby rhino. Kids would love to play with it, but that's not such a good idea. Lava does what it wants and scoffs at bulldozers and helicopters loaded with water. Live near a volcano? Tough luck if your house is in the way. Lava is not sensitive.

That's why you hear ancient stories of virgins tossed into the fiery mountain to quiet the angry gods. Countries with volcanoes are beginning to embrace the idea of lava in moderation. Forget lemons and lemonade. When life gives you volcanoes, make money. Just ask the tourist boards in Costa Rica and Hawaii. Lava can be your friend.

(on camera): But in the end, maybe lava's appeal is nothing but linguistic. Volcano words are fun. And once you start saying them, it's tough to stop. Hot lava, hot lava, hot lava.

Thomas Nybo, CNN, Atlanta.

(END VIDEOTAPE)

HEMMER: Very well done, Thomas, thank you very much.

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