The Pusat Vulkanologi dan Mitigasi Bencana Geologi (Center for Volcanology and Geological Hazard Mitigation) has raised the alert level on Tangkubanparahu, a volcano 30 km to the north of Badung in West Java, following a string of small explosions that started at about 6.20 am local time on Saturday 5 October 2013 (about 11.20 pm on Friday 4 October, GMT). The volcano's crater is noted for its hot springs, which are a popular tourist attraction, and the explosions are thought to be phreatic in origin (caused by water percolating through rock and encountering hot rocks or magma then turning more-or-less instantly to steam, resulting in an explosion). The explosions were accompanied by the release of clouds of steam and gas, which reached 300 m above the volcano's summit. A 1.5 km exclusion zone has been set up around the crater as a precaution, as similar events in the past have been followed by toxic gas emissions and small ash plumes. Tangkubanparahu erupted in February this year, prior to which it had been quiet since 1983.
A cloud of white steam above Tangkubanparahu at about 6.50 pm local time on Saturday 5 October 2013. Mega Nugraha/Tribun News.
The Indo-Australian Plate, which underlies the Indian Ocean to the south of Java, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies Java and neighboring Sumatra, along the Sunda Trench, passing under Java, where friction between the two plates can cause Earthquakes. As the Indo-Australian Plate sinks further into the Earth it is partially melted and some of the melted material rises through the overlying Sunda Plate as magma, fueling the volcanoes of Java and Sumatra.
See also Thousands evacuated following eruption on Mount Sinabung, Magnitude 6.1 Earthquake kills at least twelve people in northwest Sumatra, Activity in the Tengger Caldera, Eruption on Mount Marapi, Sumatra and Eruptions on Krakatau.
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