Sunday, December 14, 2008

The deadliest volcanic eruptions!

Volcanic eruptions are one of the deadliest natural hazards on Earth and can happen with little or no warning. Some of the greatest death tolls in modern human times have occurred as a result of a volcanic eruption. The types of volcanic hazards that are responsible for these deaths range from hazards directly associated to the eruption - such as pyroclastic flows - to hazards indirectly associated to the eruption - such as starvation.

According to an article written by J.-C. Tanguy and others titled, "Victims from volcanic eruptions: a revised database,' and published in the Bulletin of Volcanology and Geothermal Research in 1998, the five deadliest volcanic eruptions and the number of people who were killed as a result are:

Tambora, Indonesia (1815) ~ 60,000

Krakatau, Indonesia (1883) ~ 36,600

Mont Pelee, Martinique (1902) ~ 29,000

Nevado del Ruiz, Columbia (1985) ~ 23,000

Unzen, Japan (1792) ~ 15,000

Combined, these five deadly volcanic eruptions killed approximately 163,600 people and caused worldwide devastation.

The Main Causes of Death from the Volcanic Eruptions

Although each of these eruptions was powerful enough to cause pyroclastic flows, which is one of the deadliest hazards associated with volcanic activity, the main causes of death are, in some cases, surprising. The 1792 volcanic eruption of Unzen Volcano, Japan, did produce pyroclastic flows that killed about 9,500 people near the volcano; but it was the resulting tsunami that claimed the other 5,500 lives farther away.

The 1985 eruption of Nevado del Ruiz, Columbia also produced pyroclastic flows. However, these flows were perceived as non-threatening as they were small and stayed near the summit of the volcano - far away from the villages that resided at the lowest levels of the volcano's flanks. It was not until the night of Novemberr 13, 1985 that this volcano's deadliest hazard was revealed.

As the small pyroclastic flows melted snow at the summit of the volcano, large lahars, or volcanic mudflows, were being produced and making their way as a torrent down the flanks of the volcano. Without any warning, the sleeping town of Armero, Columbia was inundated by boiling hot mudflows and 23,000 people were killed in one night.

Hazards produced by the 1902 eruption of Mont Pelee Volcano on the island of Martinique were opposite to those produced by the Nevado del Ruiz eruption. The Mont Pelee eruption generated massive pyroclastic flows that traveled down the flanks of the volcano and completely destroyed the sea-side town of Saint Pierre. Virtually every single person in this town - about 28,600 people - were burned alive, suffocated or buried alive by this fast-moving ash flow. Only one person survived the destruction - a lone prisoner housed in an underground jail chamber. Lahars killed another 400 people.

The 1883 eruption of Krakatau Volcano, Indonesia, is well-known for its destruction and for the explosion that was heard almost 2,000 kilometers (1,200 miles) away. The Krakatau eruption produced pyroclastic flows and ash falls that killed about 4,600 people; but the deadliest hazard was the tsunami that was created when the flanks of the volcano collapsed into the ocean during the violent explosion. The tsunami was not expected and came as a tragic surprise to villagers living in the low-lying coastal communities surrounding the island volcano.

About 32,000 people were killed by the tsunamis, making the 1883 eruption one of the deadliest in history.

The Deadliest Volcanic Eruption in Recorded History

By far, the deadliest and most destructive volcanic eruption recorded in modern human history is the 1815 eruption of Tambora Volcano, Indonesia. This eruption - the most powerful in recorded history - produced an ash column that ejected enough volcanic material into the atmosphere to change the global climate.

Even a year after the eruption, the Tambora volcanic cloud cooled the atmosphere so much that 1816 was known in Europe and North America as "the year without a summer." About 11,000 people near the volcano died during the eruption from pyroclastic flows and ash falls. The real devastation, however, came with the failure of crops, which led to famine and disease in the region that killed another 49,000 people.

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