Volcanoes are one of the most powerful natural hazards on Earth, but supervolcanoes are so large that they have the ability to alter the world's climate. Michael Manga from the University of California, Berkeley is investigating a supervolcano that erupted hundreds of thousands of years ago, and could do so again. "When Nature Strikes" is produced by NBC Learn in partnership with the National Science Foundation and The Weather Channel. For a classroom activity related to this video, please click the Links section below.
When Nature Strikes -- Volcanoes
MARSHALL SHEPHERD reporting:
No other natural disaster has the explosive force of volcanoes. Their eruptions can send ash plumes dozens of miles into the sky and unleash rivers of 2,000-degree Fahrenheit lava. But the biggest eruptions of all come from supervolcanoes, which have the ability to impact life around the planet. They have done so in the past, and they will happen again. Michael Manga is a geologist at the University of California, Berkeley, and is funded by the National Science Foundation. He's learning a lot about the threat of supervolcanoes today, by looking at one that took place long ago.
Seven hundred and fifty thousand years ago, this beautiful area in the Sierra Nevada Mountains of northern California was the scene of an Armageddon. A volcanic eruption occurred that was so large it collapsed the mouth of the volcano and left a 20-mile-wide crater, called a caldera. Known as the Long Valley Caldera, this "super" volcano's eruption spread debris across the western half of the United States, and its impacts were felt around the world.
MICHAEL MANGA (University of California, Berkeley): The smallest particles produced by this eruption are distributed across the whole planet. You can find them in sediments pulled out of the Pacific Ocean.
SHEPHERD: Many adults today remember when the Mount St. Helens volcano in Washington State erupted in 1980, killing 57 people. The ash cloud it created reached 15 miles high. As cataclysmic as the Mount St. Helens eruption was, it pales in comparison to the eruption at Long Valley.
MANGA: When this eruption occurred, the big caldera-forming eruption, it would've been basically a thousand times bigger than Mount St. Helens in terms of the mass erupted.
SHEPHERD: Geologist Michael Manga has been studying the Long Valley Caldera to not only research this epic natural disaster, but also to understand the behavior of volcanoes around the world in order to better predict their impacts.
MANGA: Our interest is understanding how and why volcanoes erupt, why they exist. By studying fossil or old volcanoes like Long Valley, we get a better understanding of how volcanoes work.
SHEPHERD: Volcanoes come in all shapes and sizes, from flat shield volcanoes like Kilauea, in Hawaii, to towering stratovolcanoes like Mount St. Helens. But the characteristics of a volcano are determined by what's happening deep below earth's surface.
MANGA: Almost all volcanoes are ultimately controlled by what's happening deep underneath the crust. In the place we call the mantle. When mantle inside the earth rises vertically, when it gets close to the surface, it can start to melt.
SHEPHERD: This produces magma, made partly of molten rock, that rises through fractures in the Earth's crust. Various combinations of molten rock and gases are pushed further to the surface causing pressure to build up until there is a rupture, triggering a volcanic eruption. But in a supervolcano, the magma is unable to push through the crust and it pools to form massive magma chambers. Over time, the pressure continues to build until the crust finally gives way in an explosion several miles wide.
MANGA: These super volcanoes, they're so big that it's hard to imagine how big the eruption would have been.
SHEPHERD: The Long Valley Caldera is only one example. There is another supervolcano in the United States that geologists are watching even more closely.
MANGA: The other place most famous for its supervolcanoes is Yellowstone National Park. We can see magma, molten rock, under the ground. So there is a good chance at some point in the future, there will be an eruption.
SHEPHERD: The famous geysers and hot springs at Yellowstone are all examples of volcanic activity caused by magma below the surface. If Yellowstone were to have a super-eruption today, not only could it interrupt your weekend flight plans, it could also impact agriculture on a massive scale, and even alter the climate, so much in fact, that it could endanger certain species with extinction, including humans. But enough is known about volcanoes that Manga believes, for now at least, Yellowstone is still biding its time.
MANGA: There is no reason to think there will be an eruption anytime in the very near future.
SHEPHERD: With the help of scientists like Manga, more is being learned about the behavior of volcanoes and the magma inside them. The research will help improve the ability to predict not just when a volcano will erupt, but also what the eruption will look like-- information that could save thousands of lives.
The Ring of Fire is a string of volcanoes and sites of seismic activity, or earthquakes, around the edges of the Pacific Ocean. Roughly 90 percent of all earthquakes occur along the Ring of Fire, and the ring is dotted with 75 percent of all active volcanoes on Earth.
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