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Case Study 11




               Krakatau, Indonesia




               A Volcano with a History









               Malcolm Cooper

               Introduction

               Krakatau  is  a  stratovolcano  in  the  Sunda  Strait
               between the islands of Java and Sumatra in Indonesia
               (Thornton, 1997; Figure CS11.1). The name is used
               for  the  island  group,  the  main  island  (also  called
               Rakata) and the volcano as a whole. Indonesia has
               over  130  active  volcanoes  along  the  axis  of  the
               Indonesian island arc system, which are produced by
               north-eastward  subduction  of  the  Indo-Australian
               Plate. Krakatau is located directly above the subduction
               zone of the Eurasian Plate and the Indo-Australian   Figure CS11.1  NASA Earth Observatory Landsat picture
               Plate where the plate boundaries make a sharp change   of Krakatau Island area 18 May 1992
               of direction, possibly resulting in an unusually weak   Source: www.en.wikipedia.org/wiki/File:Landsat_krakatau_18may92_
               crust  in  the  region. The  best-known  eruption  of   cropped.jpg
               Krakatau culminated in a series of massive explosions
               on 26–27 August 1883, which was among the most   the eruption or from the tsunamis that followed
               violent volcanic events in modern recorded history   the  explosion,  according  to  official  records. The
               and contributed to the island’s attraction for tourists.  eruption  destroyed  two-thirds  of  the  island  of
                                                           Krakatau.  In  the  year  following  the  eruption,
               Geophysical aspects and                     average  global  temperatures  fell  by  as  much  as
               history of activity                         1.2 degrees Celsius, and weather patterns continued
                                                           to be inconsistent for years, with temperatures not
               The  first  massive  explosion  from  the  Krakatau   returning to more normal levels until 1888.
               volcano in 1883 (others were in AD535 and the   Eruptions at the volcano since 1927 have built a
               Holocene) with a VEI of 6, ejected approximately   new island in the same location, named Anak Krakatau
                    3
               21km  of rock, ash and pumice (Simkin and Fiske,   (‘Child of Krakatau’). This island currently has a radius
               1983). The  explosion  was  distinctly  heard  as  far   of roughly 2km and a high point of 300m above sea
               away  as  Perth  in  Western  Australia  (3110km,   level, and is growing by 5m each year. According to
               Furneaux, 1965). In the vicinity of Krakatau 165   some reports (SVE Volcano News, 2009) the explosive
               villages  and  towns  were  destroyed  and  132   activity at Krakatau has resumed from 22 August 2009
               seriously  damaged. At  least  36,417  (official  toll)   with  strong  vulcanian-type  eruptions  from  the
               people died, and many thousands were injured by   growing lava dome in the new crater.





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