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Www.Wired.Com - : Photo: Austin Post/USGS
Volcanoes inspire awe and terror because they can kill in so many ways -- flowing lava, suffocating ash, flood from a released lake, landslides, mudslides, burning gas, shockwaves, earthquakes and tsunamis. A volcano can kill even when it's not erupting, as happened at Lake Nyos in 1986.
We start here with three famous eruptions, modern and ancient, and then show the seven deadliest eruptions of the last 500 years, as listed by the U.S. Geological Survey.
St. Helens Blows Its Top, 1980
Mount St. Helens steamed to life in March 1980 and volcanologists knew it was ready to blow; they just didn't know exactly when. Officials closed the surrounding national forest areas to the public, but some people, like resort-owner Harry Truman, said they'd rather stay put. Others, like volcanologist David Johnston, were at observation posts deemed sufficiently far from the peak to be relatively safe.
But when the volcano erupted at 8:32 a.m. PDT on May 18, 1980, it didn't just send steam and ash up its existing crater, it blew its top off, 1,300 feet of it. And it didn't blow straight up: A whole side of the mountain that was made of fissured, rotten rock broke loose. That created a massive landslide and released a deadly cloud of pulverized rock that killed Johnston, Truman and 55 others, most of them by asphyxiation. When the ash combined with lake and stream water, the surging volcanic debris, or lahar, stormed down nearby valleys wreaking havoc.
: Photo: Richard P. Hoblitt/USGSThe Philippines' Mount Pinatubo ejected about 1.2 cubic miles of magma, sending a giant ash cloud more than 20 miles up into the stratosphere in June 1991. Ten times larger than Mount St. Helens' 1980 eruption, it was second in the 20th century only to Alaska's 1912 Katmai eruption. A million people's lives were at risk, but a good warning system saved thousands. The Philippine government evacuated 60,000 from the most dangerous slopes and valleys, and the U.S. evacuated 18,000 from nearby Clark Air Base.
The eruption shortened the volcano by 850 feet and created a new collapse caldera, or crater, 1½ miles in diameter. Ash deposits 2-inches thick covered 1,500 square miles of land, burying crops and weighing down roofs. Rain from typhoon Yunya made it even heavier, and the accumulated weight, along with the typhoon's wind and seismic shaking from the summit collapse caused roofs to cave in ... the major cause of death from the eruption. Around 350 people died.
: Photo: Bettmann/Corbis
In one of the most famous eruptions in history, Italy's Mount Vesuvius erupted suddenly in the early afternoon of August 24, A.D. 79. Glassy lava fragments, rocks, crystal and ash fell from the sky for a week, burying the Roman cities of Pompeii, Herculaneum and Stabiae on the Bay of Naples -- killing at least 3,360 people, but perhaps as many as 16,000. Among the dead was the Roman historian Pliny the Elder, who -- so great was his fascination with observing the event -- could not bring himself to flee from the danger.
So vast was the layer of volcanic debris left on the three cities that their ruins were not rediscovered until 1748. The "bodies" at left are plaster casts made in 1961 from cavities left in the debris by decomposed bodies that had been sealed in rock and dirt for 19 centuries.
: Photo: Juhász Péter
Iceland's Laki volcano produced the largest lava flow in historic times when a fissure 16-miles long sent a flow of pahoehoe (fast-moving, smooth or ropy lava) more than 40 miles in 1783. The 2.9 cubic miles of lava covered 218 square miles. The eruption continued intermittently for four months.
Fluorine gas fell to the land as hydrofluoric acid in Iceland, dissolving the flesh off livestock. Fully half the horses and cattle, as well as three-quarters of the sheep died. Famine set in, the social order broke down, and looting was rampant. Eventually, a quarter of Iceland's people died of starvation.
Sulfur dioxide gas released by the eruption traveled farther. Throughout Europe a heavy haze filtered the sun and a "dry fog" sat on the land. Excess heat caused scores of thousands of deaths. The hot summer was followed by a long, cold winter. Much of the Northern Hemisphere was 4 to 9 degrees (Fahrenheit) below normal. Siberia and Alaska had their coldest summer in half a millennium. Crop failure and famine were reported everywhere.
Iceland lost about 9,300 people, but the eventual global death toll may well have been 10 times that ? or more.
: Photo: Trisnadi/AP
Mount Kelut (or Kelud), in East Java, Indonesia, has erupted more than 30 times in the last thousand years, including a 1586 eruption that killed 10,000 people. The 1919 eruption disgorged a crater lake into nearby valleys, drowning 5,500 people. Starting in 1926, engineers built tunnels to drain the lake to prevent such catastrophes.
Steam and hot gasses rise above Mount Kelut in this photo from November 2007.
: Photo: Roger Ressmeyer/Corbis
Unzen Volcano on the island of Kyushu is about 25 miles east of Nagasaki. A month after a 1792 eruption from its current summit, the slopes of an older part of the volcanic complex, Mount Mayuyama, gave way. The resulting landslide swept through Shimabara City. It entered the sea, causing a tsunami. The landslide and tsunami together killed more than 15,000 people in Japan's worst volcanic disaster. You can still see the landslide scar above Shimabara.
Unzen erupted again in 1991, sending ash flows down its slopes at 125 mph.
: Photo: R. J. Janda/USGS
Colombia's snow-capped Nevada del Ruiz volcano exploded Nov. 13, 1985. The hot volcanic gas and ash melted the glacier and mixed with the meltwater. As the slurry tumbled downstream, it added dirt and rocks, gaining volume and density. Debris flows up to 130-feet thick swept into some inhabited river valleys at 30 mph, destroying everything in their path.
The town of Armero (left) was 46 miles from the crater, but the crush of mud and boulders hit it two-and-a-half hours after the eruption began. The river of concrete swept Armero away in a matter of minutes, killing three-quarters of its population. All together, the eruption claimed 25,000 lives.
: Photo (left half of stereoscope card) courtesy Library of Congress
The 1902 eruption of Mount Pelée in Martinique, West Indies, sent a glowing cloud of burning, poisonous gas laced with ash down the slopes of the volcano. It swept into the town of St. Pierre at 100 mph and burned or suffocated the entire population in a matter of minutes. Of the 30,000 people in town, only two (or perhaps four, depending on the account) survived. Three nearby towns suffered the same fate, as did the crews of 16 ships in the harbor. In the 10 square miles of burned-over land, as many as 36,000 people may have died, and only 30 survived.
This group of refugees in Fort de France had the apparent good fortune not to be in the path of the glowing cloud.
: Photo: flydime/Flickr
Krakatau (aka Krakatoa), in Indonesia's Sunda Strait west of Java and east of Sumatra, exploded in August 1883 with 26 times the power of the biggest H-bomb test. The collapse of the volcano into the sea generated 100-foot tidal waves that wiped out hundreds of villages and more than 36,000 lives. Much reduced, the sea wave swept around the world.
Four hours after the massive explosion, it was heard 3,000 miles away as the "roar of heavy guns." The sound was audible over 1/13 the surface of the globe, according to the Guinness Book of World Records.
The eruption also threw pumice 34 miles into the sky. Dust fell 3,000 miles away 10 days later. Islands of pumice floated on the oceans for months, and airborne particles caused vivid red sunsets around the world.
Half a century after Krakatau's epic explosion, a new volcano broke through the surface of the ocean. Anak Krakatau, for "child of Krakatau," (left) remains active and grows about five inches a week.
: Photo courtesy NASA
Tambora, which is east of Java, produced the most-powerful eruption in recorded history in April 1815. It lowered the height of the island 4,100 feet. Heavy ash fall on nearby islands killed crops, resulting in the starvation of a probable 92,000 people.
The eruption of more than 36 cubic miles of pulverized rock produced a volcanic cloud that lowered global temperatures by as much as 5 degrees Fahrenheit. The effects continued for more than a year, and some Europeans and North Americans called 1816 "the year without a summer." Further famine-related deaths almost certainly occurred.
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