Indian Ocean's hot spot
The Sunda Trench lies off the coast of Indonesia - it is a place where earthquakes occur. Here two major plates of the Earth's crust meet at a fault line: one slowly moves over the other, by just six centimetres a year.
But this movement of plates means trouble. As they push together, tension builds up over the years until suddenly it gets too much and the pressure is released, causing an earthquake.
| 
The Indian/Australian plate (light blue) is moving below the Eurasian plate (dark blue) as they meet off Sumatra.
Image: Mohamed Chlieh, Tectonics Observatory, Caltech |
|
