Two people have died and tens of thousands have been urged to leave their homes in Indonesia, following the onset of a major eruption of Kelut (or Kelud) volcano on the island of Java.
News reports suggest that over 100,000 people had been forced from their homes in the region surrounding the volcano, and Australia’s Darwin Volcanic Ash Advisory Centre (VAAC) issued an aviation warning for the plume rising from the volcano.
The February 2014 Eruption of Kelut
Following heightened seismic activity in January and early February of 2014, the the eruption began on 13 February. It increased in intensity the following day, at which stage to the Indonesian government department Badan Geologi raised the alert from level III (alert) to level IV (caution). The authorities restricted public access to a radius of 10km around the crater, while media reports indicate that ash and other airborne debris extends as far as 80km from the volcano.
Kelut: Stratovolcano Erupting
Kelut is a stratovolcano (one composed of alternate layers of ash and lava flows) in central Java. Like many of the other volcanoes in the Java-Sumatra island arc, it is typically explosive in its nature as result of its tectonic setting and the nature of the lava it produces. Because of this, and the potential for the catastrophic draining of its crater lake, leading to mudflows and floods, its eruptions tend to be highly damaging.
Although it has previously erupted only once this century (in 2008), Kelut has been periodically active; the Smithsonian Institution’s Global Volcanism Program database lists 34 known eruptions in the past millennium, usually explosive, mostly with Volcanic Explosivity Index (VEI) ratings of between 3 and 5. For comparison, the 1981 Mt St Helen’s eruption had a ranking of 5. An eruption of Kelut in 1919 killed over 5,000 people, while more than 200 died in the eruption of 1966.
Java: A Volcanic Island
Kelut is just one of 39 volcanoes on the island of Java, which is part of an active volcanic chain including the notorious volcanoes of Krakatoa and Tambora. The region’s volcanism is dictated by its tectonic setting; subduction of the Indo-Australian plate beneath the Sunda microplate causes melting of oceanic crust which then rises as hot, buoyant magma, erupting when it reaches the surface.
The nature of the magma changes as it rises (this is the process by which continents are created) creating a more viscous liquid with a higher silica content. The result is that eruptions in a subduction setting tend to be more explosive than those of hot spots (such as Hawaii) or ocean ridges – hence the destructive nature of many such events.
Java Volcano Erupts
The eruption of Kelut is, then, neither an isolated nor an unusual occurrence. In fact, at present the Badan Geologi has a second volcano, Mount Sinabung, on red alert, with amber notifications for three and yellow for a further 17. Geology dictates not only the existence of volcanoes in such settings but also the likely nature of their eruptions. Major natural disasters are always likely, and those in the region must, therefore, plan ahead.