Subduction Generation

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Subduction Generation animation

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As the Australian plate slowly pushes under the Eurasian plate, massive stresses build up in the crust. These stresses also cause the Eurasian plate to be slowly forced upwards – part of the process that builds the mountains and volcanoes of Indonesia, as well as creating the many earthquakes felt in that region of the world each year.

When the stresses get too great, the plates will suddenly slip causing massive movements in the seafloor.

The part of the crust nearest to the fault zone rapidly moves upwards by a metre or so, lifting the entire body of water above it. A hundred kilometres away the opposite may happen: the seafloor drops and the ocean above it also falls.

These two movements (the sudden rise and fall of the seafloor hundreds of kilometres apart), combine to cause a series of tsunami waves which move away from the line of the fault in both directions.