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ed. Understanding Volcanoes: A Q&A

may 10, 2010 • JUNIOR SCHOLaSTIC ONLINe RepROdUCIbLe • page 1 Of 4

Q: What is a volcano?A: A volcano is a vent, or opening, in Earth’s surface through which magma (molten rock), hot gases, and other debris pour out. Volcano also refers to the mountain-size mound that is formed after multiple eruptions have cooled and hardened around a vent. (That hardened material is lava, which is what magma becomes after a volcano erupts.)

The word volcano is thought to have come from the volcanic Italian island of Vulcano, near Sicily. Ancient Romans believed that Vulcan, their god of fire, lived beneath it.

Q: What’s the difference between an active and a dormant volcano?A: Scientists consider a volcano to be active if it has erupted in the past 10,000 years. A dormant volcano is an active volcano that doesn’t show any current signs of erupting. A volcano is considered extinct when experts don’t expect it to ever erupt again.

Q: What makes a volcano erupt?A: An eruption starts with magma—melted rock from deep inside Earth. Forced upward by intense heat, it builds up in pools called magma chambers several miles under Earth’s surface. As

magma accumulates, the pressure inside the chamber rises until the material finally erupts. Two other elements increase this pressure: explosive gases inside the magma and water, which is converted into steam at high temperatures.

Eyjafjallajokull’s eruption was triggered when a large amount of glacial ice was melted quickly by the intense heat of the magma. A Washington Post writer described it this way: “It appears that meltwater and magma produced steam quite suddenly, and the volcano popped its top like a shaken soda bottle.”

Q: Where do volcanoes form?A: The great majority of volcanoes form where the tectonic plates that make up Earth’s crust collide or pull apart. Most exist along the rim of the Pacific Ocean, where the Pacific Plate meets several continental plates. Scientists call this horseshoe-shape formation the Ring of Fire (see map, p. 3).

As many as 90 percent of the world’s volcanoes are located along the Ring of Fire. These include Mount St. Helens in Washington State. Its 1980 eruption, which killed nearly 60 people, was the deadliest volcanic event in United States history.

Q: Why does Iceland have volcanoes?A: Although it is not part of the Ring of Fire, Iceland is one of the most volcanically active places on the planet. The island is constantly being reshaped by eruptions. Iceland sits astride two tectonic plates, the North American and Eurasian. These plates are pulling apart to form what geologists call the Mid-Atlantic Ridge (see map, p. 4). Like Hawaii, Iceland also sits atop a hot spot—a place where a stream of magma comes straight up from a fixed point deep inside the Earth.

According to the Encyclopedia Britannica, Iceland has about 200 volcanoes. (About 20 are active.) An estimated one third of Earth’s lava flow since the year 1500 has come from those volcanoes. Iceland's best-known volcano, Hekla, erupted four times in the 20th century.

Iceland is also distinctive because about one tenth of its surface area is covered by glaciers. A majority of the island’s eruptions happen under glacial ice. Eyjafjallajokull is a glacier—its name is Icelandic for “island-mountain glacier”—with an icecap covering a volcano. Its last recorded activity was in 1821, when it erupted on and off for a little more than a year.

This spring, Iceland’s Eyjafjallajokull (AY-yah-fyah-lah-YOH-kuul) volcano erupted. The world was again reminded of the awesome power of this mysterious natural force. For more than a week, ash from the volcano grounded more than 100,000 flights into and out of European airports. Here is some basic information about volcanoes in general and Eyjafjallajokull in particular.

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may 10, 2010 • JUNIOR SCHOLaSTIC ONLINe RepROdUCIbLe • page 2 Of 4

Q: Why did Eyjafjallajokull’s 2010 eruption cause such a disturbance?A: The main eruption, which began on April 14, sent up a massive plume of ash. At its peak, this cloud reached 33,000 feet. As the eruption continued over several days, winds carried the ash far to the southeast over northern and central Europe (see map, p. 4). Air traffic in this area was shut down because authorities feared that the ash would cause serious damage to jet engines.

For more than a week, flights in and out of some of the busiest airports in the world were canceled. This action stranded hundreds of thousands of travelers and resulted in the largest peacetime disruption of air traffic ever. Business all over the world was affected. For instance, flower exporters in Kenya suffered serious losses when they could not get their wares to their usual markets.

The eruption did not at first affect Iceland’s main airports. These are in Reykjavík (RAY-kyuh-VEEK), Iceland’s capital, located in the opposite direction from which the ash cloud originally blew. Eventually, shifting winds did close Reykjavík’s airports for three days.

Q: How does flying through volcanic ash threaten an airliner?A: The numerous particles of rock and sand in volcanic ash can be sucked into jet engines, clogging their smallest parts. Also, ash can turn into a form of glass when it passes through the high temperatures inside a jet engine. Jet engines have been known to

shut down when passing through an ash cloud.

Q: How did the latest eruption affect Icelanders?A: The people immediately affected were farming families who live in the area of the volcano. When Eyjafjallajokull erupted, it melted a huge amount of glacial ice, sending a torrent of meltwater rushing down its sides. Some 800 people had to be evacuated as the floods destroyed roads, bridges, and buildings. Over the following days, thickly falling ash threatened to ruin farmland, cave in roofs of houses, and kill animals. (Fluorine gas in the ash is highly toxic to livestock.)

Q: Could Eyjafjallajokull’s eruption trigger any other volcanoes?A: It is possible. After each of Eyjafjallajokull’s three previous recorded eruptions (in the years 920, 1612, and 1821), its neighbor Katla also awakened. (Katla erupted on its own in 1918.) This could be trouble. Katla, also located under a glacier, is one of the largest volcanoes in Europe. Its eruption could cause even worse flooding.

Q: Will the eruption have any effect on climate change?A: Experts say that the cloud of ash did not travel at a high enough altitude to spread through the global atmosphere. However, it is possible that climate change could increase the likelihood of eruptions in the future. Heavy glacial ice serves to limit volcanic activity. If too much glacial ice were to melt, the energy that causes eruptions could be more freely released.

Q: What was the largest volcanic eruption in history?A: The largest eruption in recorded history happened on the island of Sumbawa, today part of the country of Indonesia and located along the Ring of Fire. In April 1815, that island's Mount Tambora spewed 24 cubic miles of ash and gases into the atmosphere. About 10,000 islanders were killed by the flow of lava and by tsunamis that accompanied the eruption. An additional 80,000 people in the region died from a famine as a result of the damage to farmland. The eruption was so powerful that it blocked out sunlight, lowered temperatures, and affected crop production around the planet. Places as far away as North America experienced snows and frosts in June, July, and August of 1816—“the year without a summer,” many people called it.

Q: Who studies volcanoes?A: A vulcanologist is a scientist who specializes in the formation, distribution, and classification of volcanoes.

maIN SOURCeS: Encyclopedia Britannica, United States geological Survey, Icelandic met Office, National Geographic, World Book Encyclopedia, news accounts

Click here to read more about volcanoes.

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may 10, 2010 • JUNIOR SCHOLaSTIC ONLINe RepROdUCIbLe • page 3 Of 4

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may 10, 2010 • JUNIOR SCHOLaSTIC ONLINe RepROdUCIbLe • page 4 Of 4

ATLANTICOCEAN

ARCTIC CIRCLE

ICELAND

Major volcano

0 80 MI

NORTH AMERICANPLATE

EURASIANPLATE

Reykjavík

ICELAND

VestmannaeyjarKatla

Vatnafjöll

Grímsvötn

Loki-Fögrufjöll

Krafla

Hekla

VestmannaeyjarKatlaEyjafjallajokull

Vatnafjöll

Grímsvötn

Loki-Fögrufjöll

Krafla

Hekla

ICELANDICELANDATLANTIC

OCEAN

Eyjafjallajokull volcano

A F R I C A

Mid-Atlantic Ridge

Extent ofvolcanic

ash cloud as ofApril 19, 2010

Extent ofvolcanic

ash cloud as ofApril 19, 2010

0 500 MI

Eyjafjallajokull

EU R O P E

EU R O P E

ATLANTICOCEAN

ARCTIC CIRCLE

ICELAND

Major volcano

0 80 MI

NORTH AMERICANPLATE

EURASIANPLATE

Reykjavík

ICELAND

VestmannaeyjarKatla

Vatnafjöll

Grímsvötn

Loki-Fögrufjöll

Krafla

Hekla

VestmannaeyjarKatlaEyjafjallajokull

Vatnafjöll

Grímsvötn

Loki-Fögrufjöll

Krafla

Hekla

ICELANDICELANDATLANTIC

OCEAN

Eyjafjallajokull volcano

A F R I C A

Mid-Atlantic Ridge

Extent ofvolcanic

ash cloud as ofApril 19, 2010

Extent ofvolcanic

ash cloud as ofApril 19, 2010

0 500 MI

Eyjafjallajokull

EU R O P E

EU R O P E