Posted by: maximos62 | December 9, 2016

Nusantara: Earthquakes and Vulcanism

I began the day thinking about the Aceh earthquake and reading the press on the latest relief efforts.

This set me thinking again about volcanoes and earthquakes in Indonesia.

According to the Smithsonian Institute there are 1,337 active and extinct volcanic features in Indonesia. Andesite volcanoes associated with subduction predominate. Over the past 400 years 80 Indonesian volcanoes have been active and 64 are Andesite and Basaltic Andesite producing. 48 of these are strato-volcanoes the most explosive types.

agungbat

Mt Agung last erupted in 1964.

Looking for resources on volcanoes and earthquakes I found this brilliant animation showing global volcanic and earthquake activity since 1960.

Subduction, Strato-volcanoes and Earthquakes

To the nortn Australia, ocean floor, the leading edge of the India-Australia earth plate in the region, collides with the Eurasian plate. This happens a little south of the Indonesian archipelago along Indonesia. The India-Australia plate is forced down below the Indonesian archipelago. As the India-Australia plate descends along this collision zone it forms the deep sea Java Trench. This narrow trench includes the deepest point of the Indian Ocean, over 7,700m below sea level.

indianaus-plate

When one colliding plate slides below the other plate the process is known as subduction. The India-Australia plate has been subducting below the Indonesian front for 70 million years, to the north it collides with the Eurasian plate to cause the uplift of the Himalayas.

Parts of the plate may have descended to depths of 1,200km below Indonesia. The descending plate triggers the many, large and often deep earthquakes felt in Indonesia. Friction, compression and heat from the earth’s mantle promotes melting in the sub ducting plate edge and in overlying rocks. Molten materials rise up as magma and erupt at the surface, where they form Indonesia’s volcanoes. It is the process that provides the molten material feeds Indonesia’s volcanic growth.

Earthquakes can either be the direct result of this tectonic movement or more localised events associated with one particular volcanic system.


Responses

  1. […] looks at the geological reasons for Indonesia’s […]


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Categories

%d bloggers like this: