Java: Some of the Most Volcanically active Real Estate on the Planet

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Java: Some of the Most Volcanically Active Real Estate on the Planet

The island of Java in Indonesia seen in a 2006 MODIS image. Volcanoes and ash plumes are labelled in white. Red squares are thermal anomalies – fires or actively erupting volcanoes.

One shot from space, 18 potentially active volcanoes. This shot is only part of the island of Java in Indonesia and the dozen-and-a-half volcanoes seen are only a portion of all the volcanoes on the island – the Global Volcanism Program lists no less than 39 potentially active volcanoes across the island. This represents only a fraction of the over 150 potentially active volcanoes (76 of which have had historical eruptions) across Indonesia, giving it the largest number of potentially active volcanoes for any country on Earth – along with one of the highest proportions of people living near active volcanoes.


This NASA Earth Observatory image was taken on June 15, 2006 and shows two of the 18 volcanoes producing ash plumes – Merapi to the west (left) and Semeru to the east (right). Currently, there are six volcanoes on Java listed as on Alert Status 2-3, meaning they are showing signs of unrest above background. The two most active right now are off the image – Papandayan in West Java and Ijen in East Java.

Across all of Indonesia, the last two Global Volcanism Program Weekly Volcanic Activity Reports (for February 1-7 and February 8-14) list 6 volcanoes across Indonesia that have shown signs of changing activity – some have seen their rumblings decline (Ijen, Papandayan) while others have seen no change in their heightened activity or an increase (Dukono, Semeru, Lokon-Empung, Galunggung). This increase in the Alert Status at Galunggung was precipitated by an increase in temperature and color of the summit crater lake – signs that there is likely increased degassing, possibly from rising magma, into the bottom of the lake. All of this activity is perfectly normal for an active volcanic arc like Indonesia, where the Indo-Australian plate is being subducted under the Eurasian plate along the southern edge of the island chain. It also explains the high occurrence of earthquakes in Indonesia as the friction on the subduction builds and is released periodically in the form of seismic events. All in all, Java is one of the most geologically active spots on the planet.

Image: Part of Java in Indonesia, image in June 2006. Image courtesy of the NASA Earth observatory.

Erik Klemetti is an assistant professor of Geosciences at Denison University. His passion in geology is volcanoes, and he has studied them all over the world. You can follow Erik on Twitter, where you’ll get volcano news and the occasional baseball comment.
Follow @eruptionsblog on Twitter.

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