Tsunamis

 

Devastation caused by the March 2011 tsunami, Japan © Flickr/yisris

A tsunami is a series of enormous traveling ocean waves of extremely long length generated primarily by earthquakes occurring below or near the ocean floor. They may also be generated by underwater landslides and volcanic eruptions, or meteorites. Tsunami waves are distinguished from ordinary ocean waves by their great length between wave crests, often exceeding 100 kilometres or more in the deep ocean, and by the time between these crests, ranging from 10 minutes to an hour. In the deep ocean, tsunami waves travel at over 800 km/h, with a short wave height of only a few tens of centimetres or less. As they reach shallow coastal waters, the waves slow down and the water can pile up into a wall of destruction dozens of metres or more in height. Large tsunamis have been known to rise over 30 metres and even a tsunami 3-6 metres high can be very destructive and cause many deaths and injuries. Although 60 percent of all tsunamis occur in the Pacific Ocean, they can also threaten coastlines of countries in other regions, including the Indian Ocean, Mediterranean and Caribbean Seas, and the Atlantic Ocean.

Mangroves, coastal forests, home gardens, agroforestry systems and trees in coastal landscapes can be damaged by tsunamis. Trees may be snapped and uprooted by waves and strong currents. Observed changes in topography, soil salinity and freshwater input may also adversely affect mangroves, coastal forests and other trees in the longer term.

last updated:  Friday, June 28, 2013