The DART system (Deep-ocean Assessment and Reporting of Tsunamis) warns countries of approaching tsunamis so that coastlines can be evacuated.
Each DART station consists of a buoy on the surface and a pressure sensor on the ocean floor. The sensor detects pressure changes in the water and transmits them up to the surface buoy. The buoy transmits the data to warning centres around the world.
There are 56 DART stations: in the Pacific Ocean, Indian Ocean and Caribbean Sea.
Photo: an Australian DART buoy floats in the Pacific Ocean.