What Are Tsunamis, and What Causes Them?

(Based on the December 26th attack)

What Are Tsunamis, and What Causes Them?

Tsunamis are ocean waves produced by earthquakes or underwater landslides. The word is Japanese and means "harbor wave," because of the devastating effects these waves have had on low-lying Japanese coastal communities. A tsunami is a series of waves that can travel at speeds averaging 450 (and up to 600) miles per hour in the open ocean. As the waves approach the coast, their speed decreases and their amplitude increases.

Tsunamis are most often generated by earthquake-induced movement of the ocean floor. Landslides, volcanic eruptions, and even meteorites can also generate a tsunami. Areas at greatest risk are less than 25 feet above sea level and within one mile of the shoreline.

From an initial tsunami generating source area, waves travel outward in all directions much like the ripples caused by throwing a rock into a pond. As these waves approach coastal areas, the time between successive wave crests varies from 5 to 90 minutes.

Their Effect...

...on lives

Most deaths caused by a tsunami are because of drowning. Associated risks include flooding, contamination of drinking water, fires from ruptured tanks or gas lines, and the loss of vital community infrastructure.

...on hygiene

Contrary to popular belief that rapid burial is essential to prevent outbreaks of disease, post-disaster, a report by the Pan American Health Organisation (PAHO) says: " dead bodies pose a negligible risk ".

...on the infrastructure

With most people focusing their attention on the losses suffered by the fishing community, in the aftermath of the tsunami, Tamil Nadu's (deprived of aid) coastal farmers have to come to terms with destroyed crops, damaged soil and devastated livelihoods.

Scores of farmers in Tamil Nadu face an uncertain future as the water that engulfed their fields, washing away crops, has left the soil saline and uncultivable. Although the extent of the damage is yet to be fully assessed, officials say that a substantial proportion of cultivable land has been contaminated by salt water.

...on tourism

Tourism constitutes a major sector of the Indian economy and it will be correct to say that it has been affected due to the tsunami tragedy.

Tourists who were planning to go to the south - eastern coastal regions have cancelled their bookings at the last few minutes. Travel agents have had to deal with these last-minutes cancellations and there will be an immediate impact on the travel industry for India.