What other things could create a tsunami?
Sometimes when an ocean island collapses it causes a huge displacement of water which can also create a tsunami. Very rarely, a tsunami can be created by a giant meteor hitting the sea!
Scientists found traces of a huge meteor rock that collided with the Earth 3.5 billion years ago and landed in the sea, which may have created a giant tsunami that drastically changed coastlines and wiped out almost all life on land.
Read More: Japan Tsunami, 11 March 2011