Volcano

KRAKATAU

Eighteen hundred four years—almost to the day—after Pompeii was buried, an even larger volcanic catastrophe occurred half a world away. On Aug. 26–28, 1883, Krakatau, between the Indonesian islands of Sumatra and Java, erupted, destroying two-thirds of the island and discharging an immense cloud of dust that spread across the Earth, lowering global temperature by as much as 1.2 degrees C the following year.

Krakatau's explosions also produced forty-meter high tsunamis that hurled ashore pieces of coral weighing 600 tons, and whose residual waves were observed as far away as Cape Horn and England. More than 36,000 people died in the disaster.

Still a Threat

Like Vesuvius (which also erupted in 1872, 1906, and 1944, as well as several other times), Krakatau is still active; stirrings were recorded as recently as April 1996. And there are hundreds of other active volcanoes worldwide (Indonesia alone has 130). Many of these are submarine volcanoes whose activity goes undetected, but more than 500 volcanoes have had significant eruptions in recorded history.

Historical Volcanoes

Notable eruptions within historic times have been those of Vesuvius, in Italy (A.D. 79, 1906, and other times); Tambora, in Indonesia, where between 30 and 50 cu mi (125–210 cu km) of molten and shattered rock were blown into the air (1815); Krakatoa, near Java, material from which was sent 17 mi (27 km) into the atmosphere (1883); Parícutin, in Mexico, the volcano that began in a cornfield (1943); Hibok Hibok, on Camiguin island in the Philippines, which killed 84 people (1948); Besymianny, in Kamchatka, where 2 cu mi (8 cu km) of material were hurled into the air (1956); the peak of Tristan da Cunha, whose eruption caused the entire settlement to be evacuated (1961); Agung, in Bali, which killed 1,100 people (1963); Mt. St. Helens in Washington, which exploded with an energy equivalent to 10 million tons of TNT, killing 35, with 25 missing (1980); El Chichon in Mexico, which expelled about 500 million tons of ash and gas (1982); and Mt. Pinatubo in the Philippines, which killed over 500 people and ejected over 2 cu mi (8 cu km) of material (1991). Other notable volcanoes are Cotopaxi and Chimborazo (Ecuador), Iztaccihuatl and Popocatépetl (Mexico), Lassen Peak and Katmai (United States), and Etna (Sicily). Mauna Loa (Hawaii) is the world's largest active volcano, projecting 13,677 ft (4,170 m) above sea level and over 29,000 ft (8,850 m) above the ocean floor; from its base below sea level to its summit, Mauna Loa is taller than Mt. Everest. In 1963 the birth of the volcanic island Surtsey near Iceland was observed. In November of that year events began with a submarine eruption along the Mid-Atlantic Ridge. Eruption followed eruption until June, 1967, by which time the island stood 492 ft (150 m) above sea level and covered an area of almost 2 sq mi (3 sq km). The island has not grown since the last eruption, and it is presently volcanically quiet.

VESUVIUS

One of the world's most noted volcanoes, Vesuvius (Vesuvio) forms a dramatic backdrop to the Bay of Naples. The historically active cone of Vesuvius was constructed within a large caldera of the ancestral Monte Somma volcano, thought to have formed incrementally beginning about 17,000 years ago. The Monte Somma caldera wall has channeled lava flows and pyroclastic flows primarily to the south and west. Eight major explosive eruptions have taken place in the last 17,000 years, often accompanied by large pyroclastic flows and surges, such as during the well-known 79 AD Pompeii eruption. Intermittent eruptions since 79 AD were followed by a period of frequent long-term explosive and effusive eruptions beginning in 1631 and lasting until 1944. The 1631 eruption was the largest since 79 AD and produced devastating pyroclastic flows that reached as far as the coast and caused great destruction. Many towns are located on the volcano's flanks, and several million people live within areas potentially affected by eruptions of Vesuvius.