KRAKATAU VOLCANO

Several years of regional seismicity culminated in the famous caldera-forming eruption of August 1883 (Verbeek, 1886; Judd, 1888). Earthquakes were felt in west Java and eastern Sumatra 5-6 years before the 1883 eruption, and in northern Australia in the 3 years before the eruption. On 1 September 1880, a strong earthquake damaged the First Point lighthouse on the west end of Java (70 kilometers south-southwest of Krakatau). more earthquakes were felt at First Point on 9-10 May 1883 and at Katimbang (40 kilometers north-northeast) during 15-20 May 1883. None of the above-mentioned earthquakes is known to have been of volcanic origin and centered beneath Krakatau; more likely, they reflect a buildup and release of tectonic stress in the sunda Strait area.

A mild ash and steam eruption began from Perbuwatan on 20 May 1883, and similar eruptions continued for 3 months. At times several vents were in eruption simultaneously. On 11 August, vigorous ash-laden gas columns rose from the main crater of Perbuwatan, the former vent of Danan, and from the foot of Danan; in addition, "no fewer than eleven other foci of eruption could be observed on the visible portions of the island, from which smaller steam-columns issued and ejections of ash took place" (Judd, 1888, p.13). At least some of the early ash was basaltic, suggesting that intrusion of basaltic melt into the silicic reservoir may have played a role in initiating these eruptions (Francis and Self, 1983). The small eruptions intensified on 24 August 1883 and culminated in the famous, climactic explosion of 27 August 1883 (Verbeek, 1886; Judd, 1888; Simkin and Fiske, 1983).

Earthquakes and rumbling, not demonstrably from Krakatau, were noted in 1898 (Koninklijk Magnetisch en Meteorologisch Observatorium te Batavia, 1899). On 13 August 1913, a strong tectonic earthquake occurred in the Bantam-Krakatau region, damaging the First Point lighthouse. Fishermen where were on the islands of Krakatau reported that part of the caldera wall collapsed. They also reported that at 1000 hours a "column of fire" rose out of the crater, whereupon they heard a cannonlike sound and fled (Visser, 1920). There are no independent reports of eruptions of Krakatau in 1913, and we suspect that only a landslide occurred.

The 1883 eruption of Krakatau Volcano, located in the Sunda Straits between the islands of Sumatra and Java, Indonesia, provides an excellent example of an eruption-caused tsunami. A series of tsunamis washed away 165 coastal villages on Java and Sumatra, killing 36,000 people. The larger tsunamis were recorded by tide gauges as far away as the southern coast of the Arabian Peninsula-more than 7,000 kilometers from Krakatau!

 

 

 

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