How did the Indian Ocean tsunami happen?

Answer:
The December 26, 2004 tsunami occurred at a plate boundary, a few miles off the coast of Sumatra, Indonesia. A natural sensation called 'subduction' occurred. That is when a plate slides over or under another plate. There was an earthquake and also a displaced water mass trying to regain it's equilibrium position. Shockwaves were sent in all directions.
First answer by Mairmair. Last edit by Mairmair. Contributor trust: 0 [recommend contributor recommended]. Question popularity: 1 [recommend question].