Say tsunami and up pops a mental image of a single, giant wave rising out of the ocean to swallow cities whole. In reality, tsunamis (meaning 'harbour wave' in Japanese) are a series of waves that start small and grow as they approach land. They are the result of oceans attempting to smooth out their surface after a disturbance.

Tsunamis are triggered by any phenomenon that causes a large part of the water’s surface to rise or drop relative to normal sea level. These events are usually the result of earthquakes occurring along undersea fault lines, the cracks in the earth’s crust between tectonic plates. When these plates collide or grind against each other, they can elevate, lower, or tilt major sections of the ocean floor, suddenly offsetting the level of water at the surface. The displaced water then rushes to level out, causing a tsunami. The waves travel outward in all directions from the place where the earthquake occurred, just like the ripples created when a stone is thrown into a lake.