Volcano

According to the United States Geological Survey, between 50 and 60 volcanoes erupt each year, usually in sparsely populated areas. In the past 500 years more than 200,000 people have died as a result of volcanic activity. Between 1900 and 1986, volcanoes directly or indirectly killed an average of 845 people each year. The 1980 eruption of Mount St. Helens, the last volcanic eruption within the contiguous United States, killed 57 people.

During the 1980s and 1990s the science of volcanology greatly improved our knowledge of volcano behavior. Consequently, volcanologists can now warn civil authorities when eruptions are likely to occur. Mt. Pinatubo, a composite volcano in the Philippine Islands, erupted explosively in 1991. In 1997, a pyroclastic flow burst from the Sourfriere Hills volcano on the island of Montserrat in the Caribbean. Lives were lost in both of these disasters; however, many more lives were saved by timely evacuation of the populations flanking the volcanoes.

Mt. Mazama, which existed in what is now southern Oregon, erupted and collapsed nearly 7000 years ago, creating Crater Lake. The story of the eruption evolved into a Native American myth, the Battle of Llao and Skell, that was eventually translated to English. Twentieth century geologists found the myth to be an accurate description of the development of a caldera nearly 250 generations ago.

An ash fall from Mt. Vesuvius buried the Roman city of Pompeii in A.D. 79. The volcano struck down the people where they lived, and preserved the shapes of their bodies where they fell in the ash. Pompeii is a remarkable volcanic disaster because much of the city was preserved along with the names, portraits, writings, and even graffiti of those who lived there. Plaster casts were made of them as the city was excavated in the late 1700s. The nearby city of Herculaneum was covered by a pyroclastic flow that destroyed it in seconds.

Kuwae, in Melanesia, erupted in 1453. A legendary chieftain hastily assembled the population, moving them to safety in the last-minute. The eruption destroyed all remaining life on the island, and split it into several sections. Decades after the caldera eruption, the people returned to the new archipelago of which Epi and Tongoa are the principal islands. Eruptions of this size affect weather and climate worldwide, and cause peculiar optical effects in the atmosphere. Ash in the stratosphere causes the sky to appear strangely colored and dims the sunlight. Some geologists speculate that the eruption's optical effects in 1453 may have filled the defenders of Constantinople with superstitious dread, hastening the city's demise.

The Laki fissure eruption of 1783 produced huge volumes of fluorine gas, which poisoned the grass that fed Icelanders' flocks. Approximately 229,000 animals died as a result, and 10,000 Icelanders subsequently starved to death, reducing the population by one-fifth. Benjamin Franklin observed the blue haze that covered Europe, and deduced that the pollution from the eruption must have caused the abnormally cold winter that year.

Tambora, an Indonesian composite volcano, erupted and collapsed in 1815, chilling the world for the next year. The explosion destroyed the volcano's summit and filled the stratosphere with volcanic dust, significantly decreasing the amount of sunlight that reached Earth's surface. Tambora's collapse killed 10,000 people, and another 80,000 starved to death as a result of crop losses.

Krakatau, another Indonesian composite volcano, erupted and collapsed in 1883, causing worldwide cooling similar to Tambora. The collapse was heard by people 2,500 mi (4,000 km) away. Tsunamis killed 36,000 people in coastal Java and Sumatra. The atmospheric effects of this eruption in the equatorial latitudes included brilliant green sunrises, sunsets, and moonrises, followed by blue sunlight throughout the day.

Volcanologists know of even larger caldera eruptions in the geologic past than those in this list. Likewise, there are many volcanoes that have the potential to erupt catastrophically in the near future. Some of them are located in the world's most populous areas: Seattle, Washington; Guadalajara, Mexico; the Bay of Naples, Italy; and Rabaul, Papua New Guinea.