By Frank Wesselingh, Naturalis Museum, Leiden
The amazing volcanoes that straddle Java are here for a reason. This is a short essay on how Indoaustralian nutrients enrich day-to-day Indonesian life.
The first physical disorders are already occurring within our group: toothache here, bronchitis there and some of the inevitable stomach disorders. However, the team is in good spirits, certainly after an inspiring day of workshop that included some of the basics of writing a blog.
So here you have a blog which tries to explain why there are so many volcanoes around us, written by your molluscan palaeontologist Frank.
There are really many volcanoes on Java, I think seventeen of them are classified as active. Many of them have the characteristic conical volcano shape that I learnt as a kid volcanoes should look like. Java is located on the southeast tip of the Eurasian continent, the large plate on which the United Kingdom (and Ireland and the rest of mainland EU) is located.
Only a few hundred kilometers to the south of Bandung there is the plate that contains India and Australia, the Indoaustralian plate. That plate and the Eurasian plate are converging. In some places the plates collide and huge mountains, the Himalayas are uplifted. In other areas, such as south of Java, the Indoaustralian plate dives under the Eurasian plate, because of the slightly heavier weight of the former.
the process of making a volcano
The submerging plate is drawn into the hot mantle and melts: magma begins to form. Because the submergence occurs under an angle, the melting takes place deep under the Eurasian plate. When enough magma is formed it will seek its way upward and will form volcanoes, like those on Java. When you encounter a row of volcanoes, like here, or in southern Alaska or Peru, you can be certain there must be a subducting plate nearby.
A part of the lava and ashes spewed by the Java volcanoes has an Indoaustralian origin! They are rich in nutrients and make very fertile ground. You can see this in the landscape. Crawling up the flanks of the volcanoes are vegetable plots and villages. People live in places they’d better not and as shown by the recent Merapi eruption, the likelihood of casualti increases.
the fertile grounds around the volcano