On 26 December 2004, a magnitude 9.3 earthquake at the Australian-Eurasian plate boundary caused parts of the seabed near Sumatra to rise by several metres, displacing billions of gallons of seawater. This “step” in the ocean fell back under gravity and the disturbance caused three giant ripples to spread outward from the earthquake’s epicentre.

Two hours after the earthquake radar satellites recorded the tsunami’s waves at less than 60cm (24 inches) high in deep water. But, funnelled along giant channels in the seabed, when they reached shallow water they slowed and swelled. The tsunami struck the north-west coast of Sumatra first and most powerfully. Along parts of the coastline, tsunami waves rose to 30m (100ft) above sea level as they crashed against the shore.

Within 15 minutes of the earthquake, the tsunami had engulfed northern Sumatra’s city of Banda Aceh, killing tens of thousands of people. The tsunami continued rippling outward to hit the coast of Thailand within two hours and Sri Lanka within three. Some eight hours after it began the tsunami reached Somalia on Africa’s eastern coast where it claimed about 300 more lives.

The tsunami’s destructiveness lies in its massive walls of water that slam against gently shelving coasts. It sweeps boats, dwellings and people before it. The Asian tsunami claimed more than 230,000 lives and left one million coastal inhabitants homeless and their communities shattered.