How Fast Is Tsunami at Shore?

A tsunami slows from over 800 km/h in deep ocean to 65 km/h as it approaches shore — but builds enormous height as it does. The 2004 Indian Ocean tsunami reached 30 metres tall as it hit the Indonesian coast.

A tsunami slows from 800 km/h in deep ocean to 65 km/h at shore — but the energy compresses upward, building staggering height.

• Slower than in deep ocean but towers higher
• 2004 wave reached 30 m tall