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Mayon Volcano, 1984, via Wikimedia Commons // Public Domain
Mayon Volcano, 1984, via Wikimedia Commons // Public Domain

15 Explosive Facts About Volcanoes

Mayon Volcano, 1984, via Wikimedia Commons // Public Domain
Mayon Volcano, 1984, via Wikimedia Commons // Public Domain

They’re amazing. They’re dangerous. They’re portals to the hot, living interior of the Earth. Even small-ish ones can have a global impact. Here are 15 explosive facts about volcanoes.

1. THE VOLCANIC EXPLOSIVITY INDEX MEASURES THE STRENGTH AND SIZE OF ERUPTIONS.

Created in 1982 by Chris Newhall of the United States Geological Survey and Stephen Self of the University of Hawaii, the VEI quantifies the strength of volcanic eruptions by measuring the volume of pyroclastic material spewed by a volcano, including volcanic ash, tephra (fragments of volcanic rock and lava), pyroclastic flows (fast-moving currents of gas and tephra), and other debris. The height and duration of the eruption are also factored in. The scale ranges from 1 to 8, and each step indicates a tenfold increase of ejecta. Fortunately, there hasn’t been a VEI-8 eruption in the past 10,000 years.

2. "WAH WAH SPRINGS" SOUNDS KIND OF FUN. IT WAS ACTUALLY DEVASTATING. 

One of the biggest eruptions ever occurred about 30 million years ago in what is today eastern Nevada and western Utah, when a supervolcano exploded 3500 cubic kilometers of magma over an area of about 12,000 square miles. The eruption left behind deposits of debris 13,000 feet deep. Consider that the 1883 eruption of Krakatau, in Indonesia, was heard thousands of miles away—and yet it was a minor burp compared to Wah Wah Springs, a VEI-8 eruption.

3. LAVA IS THE LEAST OF YOUR WORRIES. 

Garden of the Fugitives, Pompeii. Image Credit: Lancevortex via Wikimedia Commons // CC BY-SA 3.0

Lava generally moves too slowly to be the biggest threat from an eruption—but that’s not the case with pyroclastic flows. These super-hot, fast-moving currents of gas and tephra did in history’s most famous volcano victims: the residents of Herculaneum and Pompeii. The flow that hit Herculaneum was as hot at 500 degrees—enough to boil brains and vaporize flesh—while the later, cooler wave that hit Pompeii “cooked” people’s flesh, as the BBC puts it, but left their bodies intact; they were preserved by the falling volcanic ash. 

4. JUST FOR FUN, THERE ARE 10 WAYS AN ERUPTION CAN KILL YOU. 

As Io9 recounts, flying shrapnel, scalding-hot seawater, falling into a lava tube, poisonous gases, and volcanic smog, or vog, can also do you in.

5. THERE ARE THREE TYPES OF VOLCANIC ERUPTIONS. 

Magmatic eruptions involve the decompression of gas within magma that propels it forward. Phreatic eruptions are driven by the heat from magma creating superheated steam. Phreatomagmatic eruptions are caused by the interaction of water and magma.

6. VOLCANOLOGISTS ARE CONTINUOUSLY KEEPING TABS ON ACTIVITY ALL OVER THE WORLD.

One of the many initiatives tracking potentially dangerous activity is the Global Volcanism Program of the Smithsonian National Museum of Natural History. It also puts out a weekly report in conjunction with the USGS that features a map. The International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) especially monitors the so-called Decade Volcanoes—16 volcanoes that are potentially hazardous due to their history of large, destructive eruptions and proximity to populated areas. Among them are Rainier, Sakurajima, Vesuvius, and Santorini.  

7. THERE ARE VOLCANOES ON OTHER PLANETS AND MOONS IN OUR SOLAR SYSTEM.

Plumes on Io captured by the Galileo spacecraft. Image Credit: NASA/JPL/University of Arizona

That Jupiter’s moon Io is volcanically active has been known since 1979, when Voyager 1 imaging scientist Linda Morabito discovered the first evidence of active volcanism on a body other than Earth. But it’s far from alone. For instance, while Mars’s volcanoes appear to be either dormant or extinct, recent evidence from the Venus Express spacecraft suggests that many of Venus’s volcanoes are active.

8. SHARKS HANG OUT IN ONE VOLCANO.

Scientists recently recorded video of sharks happily swimming around in the acidic, hot, ash- and gas-filled waters near the Kavachi underwater volcano in the Solomon Islands, which is a mere 66 feet below the surface. This suggests extremophiles may be even more diverse than we thought.

9. THE USGS’s ALL-TIME BEST-SELLING MAP FEATURES VOLCANOES.

"This Dynamic Planet" is now in its third edition. This map [PDF] features more than 1500 volcanoes, 44,000 earthquakes, and 170 impact craters, as well as the major, minor, and micro tectonic plates whose movement creates these features. About 60 of Earth’s 550 historically active volcanoes blow every year.

10. AN EARLY 19TH-CENTURY ERUPTION IN THE PACIFIC WAS WORLD CHANGING.

Gillen D’Arcy Wood argues in his book Tambora: The Eruption That Changed the World that the 1815 eruption of the volcano on the Indonesian island of Sumbawa, which created a massive sulfate dust cloud that fundamentally altered the planet’s climate for three years, led to such diverse impacts as the first worldwide cholera pandemic, expanded opium markets in China, the U.S.’s first economic depression—and Mary Shelley’s Frankenstein.

11. A VOLCANO STAMP SOLD CONGRESS ON THE PANAMA CANAL.

Before the Panama Canal opened in 1915, rival proposals for an Atlantic–Pacific link included a plan to carve a canal through Nicaragua, which had a lot more fresh water and much less deadly malaria than Panama. It also has significant volcanic activity, and in the early 20th century, one of its stamps featured an erupting volcano. In 1902, just before a U.S. congressional vote, a pro-Panama Canal French engineer sent this stamp to all 90 senators to hype the volcanic threat in Nicaragua. Panama got the vote by a slim margin. Today Nicaragua says it’s building the canal with help from a Chinese funder.   

12. SPEAKING OF NICARAGUA’S VOLCANOES—YOU CAN SURF ONE.

Cerro Negro, a new and very active volcano that first erupted in 1850—and has blown 23 times since, most recently in 1999—has a black pebble-covered slopes you can surf down on a metal-bottomed wood board, if you're adventurous and also kind of insane. Intrigued? Here’s our 7-point guide to surfing volcanoes.

13. THE MOST VOLATILE AREA ON EARTH IS THE RING OF FIRE.

Located at the rim of the Pacific Basin, the so-called Ring of Fire is a nearly continuous chain of oceanic trenches and hundreds of volcanoes spanning some 25,000 miles that’s home to 75 percent of the world’s volcanic activity, with some 452 volcanoes (active and dormant); 90 percent of the world's earthquakes; and 22 of 25 of the biggest volcanic eruptions in the last 11,700 years.

14. THERE ARE MANY WARNING SIGNS OF VOLCANIC ACTIVITY.

According to the USGS’s Volcano Hazards Program, volcanologists keep an eye out for ground movements caused by magma forcing its way upward through solid rock; earthquakes resulting from this heaving; and changes in heat output and volcanic gases. Other indicators include cracks in the ground, small steam explosions, melting snow, and the appearance of new hot springs.

15. YOUR EUROPE FLIGHT WAS DELAYED IN 2010 BECAUSE OF AN ICELANDIC ERUPTION.

The Eyjafjallajökull volcano began erupting on April 14, 2010 and didn’t stop for six weeks, spewing magma, ash, and gas. Planes were grounded across Europe. Though the eruption was a small one, it had an outsized impact because it spread unusually far and stayed for an unexpectedly long time in the atmosphere thanks to the irregular shape of the tiny porous ash grains, as LiveScience reports.

BONUS: NASA IS TRAINING FOR LIFE ON MARS ON THE SLOPES OF AN ACTIVE VOLCANO. 

NASA’s latest training ground for life on Mars puts a 6-member team in a geodesic dome for the next year on the slopes of the Hawaii's Mauna Loa volcano, one of the Decade Volcanoes. If they want to go outside, they have to put on space suits. Still beats trying to escape poisonous gases and pyroclastic flows.   

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Geological Map Shows the Massive Reservoir Bubbling Beneath Old Faithful
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Yellowstone National Park is home to rivers, waterfalls, and hot springs, but Old Faithful is easily its most iconic landmark. Every 45 to 125 minutes, visitors gather around the geyser to watch it shoot streams of water reaching up to 100 feet in the air. The punctual show is one of nature’s greatest spectacles, but new research from scientists at the University of Utah suggests that what’s going on at the geyser’s surface is just the tip of the iceberg.

The study, published in the journal Geophysical Research Letters, features a map of the geological plumbing system beneath Old Faithful. Geologists have long known that the eruptions are caused by water heated by volcanic rocks beneath the ground reaching the boiling point and bubbling upwards through cracks in the earth. But the place where this water simmers between appearances has remained mysterious to scientists until now.

Using 133 seismometers scattered around Old Faithful and the surrounding area, the researchers were able to record the tiny tremors caused by pressure build-up in the hydrothermal reservoir. Two weeks of gathering data helped them determine just how large the well is. The team found that the web of cracks and fissures beneath Old Faithful is roughly 650 feet in diameter and capable of holding more than 79 million gallons of water. When the geyser erupts, it releases just 8000 gallons. You can get an idea of how the reservoir fits into the surrounding geology from the diagram below.

Geological map of geyser.
Sin-Mei Wu, University of Utah

After making the surprising discovery, the study authors plan to return to the area when park roads close for the winter to conduct further research. Next time, they hope to get even more detailed images of the volatile geology beneath this popular part of Yellowstone.

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Big Questions
Just How Hot Is Lava?
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Like the bubbling cheese of a pizza consumed too quickly, lava has been anointed as one of the most scorching substances on Earth. But just how hot is lava? How quickly could it consume your flesh and destroy everything in its path?

You may already know that lava is actually molten rock that oozes or spurts out of volcanoes because of the extreme temperatures found miles deep in the Earth. As the rocks melt, they begin to rise toward the surface. (Lava is typically referred to as magma until it reaches the surface.) As you can imagine, the heat that's needed to melt rock is pretty staggering. Cooler lava—relatively speaking—could be around 570°F, about the same as the inside of your typical pizza oven. On the extreme side, volcanoes can produce lava in excess of 2120°F, according to the United States Geological Survey.

Why is there so much variation? Different environments produce different chemical compositions and minerals that can affect temperature. Lava found in Hawaii from basalt rock, for example, tends to be on the hotter side, while minerals like the ones found near the Pacific Northwest's Mt. Saint Helens could be a few hundred degrees cooler.

After lava has erupted and its temperature begins to lower, it will eventually return to solid rock. Hotter lava flows more quickly—perhaps several feet per minute—and then slows as it cools, sometimes traveling only a couple of feet in a day.

Because moving lava takes its sweet time getting anywhere, there's not much danger. But what if you did, in some tremendously unfortunate circumstance, get exposed to lava—say, by being thrown into a lava pit like a villain in a fantasy film? First, you're unlikely to sink rapidly into it. Lava is three times as dense as water and won't simply move out of the way as quickly. You would, however, burn like a S'more at those temperatures, even if you wouldn't quite melt. It's more likely the radiant heat would singe you before you even made contact with the hypothetical lava lake, or that you'd burst into flames on contact.

Because lava is so super-heated, you might also wonder how researchers are even able to measure its temperature and answer the burning question—how hot is lava, exactly—without destroying their instrumentation. Using a meat thermometer isn't the right move, since the mercury inside would boil while the glass would shatter. Instead, volcanologists use thermocouples, or two wires joined to the same electrical source. A user can measure the resistance of the electricity at the tip and convert it to a readable temperature. Thermocouples are made from ceramic and stainless steel, and both have melting points higher than even the hottest lava. We still don't recommend using them on pizza.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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