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Wild Indonesia birth of an island

The Child Grows

Eruption plumesVolcanoes typically build up in fits and starts. After 1883, Krakatau was dormant until 1927, when a new cone began to build at the edge of the 1883 caldera. In 1928 alone, 22,358 earth tremors were registered by a temporary volcanological observatory on the island of Panjang, while eruption plumes were seen to reach 1,200 meters high. However, the first three attempts to break the surface formed only temporary ash-cone islands, which were destroyed by marine erosion and submarine sliding on the steep slope of the submerged caldera. The second of these islands was visited by a party of scientists in May 1929, shortly before it slipped back into the sea. They collected several insects, including a large black cricket and a brown ant. The present island, the fourth, emerged in August 1930, and over the next few years, it alternated between periods of quiet and rapid growth. At times, particularly in the early 1930s, the eruptions produced huge quantities of fine ash, which, aided by the alternating monsoon winds, have been deposited on the developing forests of Panjang and Sertung islands, a few kilometers distant (in opposite directions), causing extensive damage. By September 1932, the island was 47 meters high and had a typical low wide crater some 700 meters in diameter. By 1933, the height had increased to 67 meters, and by 1941, it had doubled again to reach 132 meters. The 1940s was a period of relatively little activity, but in 1952 and 1953, the volcano sprang back into action, producing large quantities of ejecta. This was produced in such quantities and to such heights (clouds reaching 4,000 meters at times) that once again it was carried across to Panjang and Sertung islands, damaging as much of 90 percent of their forests to a degree visible from boats passing through the group. On Anak Krakatau itself, the colonization of plants and animals was abruptly halted by these eruptions, as the vegetation was more or less eliminated. A new, high inner cone formed, that was about 500 meters in diameter, enclosing a new crater lake. The records then indicate a further period of inactivity, until 1958, with further ash eruptions occurring over the period to 1963, during which some traces of ash reached sites on the coast of Java, some 40 kilometers distant.



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