TSUNAMIA tsunami is a series of water waves caused by the displacement of a large volume of a body of water, generally an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami.

Tsunami waves do not resemble normal sea waves, because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide, and for this reason they are often referred to as tidal waves. Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in a so-called "wave train".Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous and they can affect entire ocean basins; the 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history with at least 290,000 people killed or missing in 14 countries bordering theIndian Ocean.

The Greek historian Thucydides suggested in his late 5th century BC, History of the Peloponnesian War, that tsunamis were related to submarine earthquakes, but the understanding of a tsunami's nature remained slim until the 20th century and much remains unknown. Major areas of current research include trying to determine why some large earthquakes do not generate tsunamis while other smaller ones do; trying to accurately forecast the passage of tsunamis across the oceans; and also to forecast how tsunami waves would interact with specific shorelines.

Tsunami and India

Tamil NaduThe worst affected state in India was Tamil Nadu. About 7,793 people lost their lives. In the Nagapattinam district 5,525 people died; in Kanyakumari there were 808 deaths; Cuddalore district had a death toll of 599; the capital city of Chennai had 206 people dead while Kancheepuram district saw the death of about 124 people. The number of deaths in other districts of Tamil Nadu was Pudukkottai (15), Tirunelveli (4), Ramanathapuram (6), Tiruvallur (28), Thoothukudi (3), Tiruvarur (10), Thanjavur (22), and Viluppuram (47).

In Kanyakumari, mostly the pilgrims died, who were taking a sacred dip in the sea. In Chennai, those near the Marina beach were killed; at Velankanni in the district of Nagapattinam 1,500 people were washed away.

PondicherryIn the Union territory of Pondicherry, about 30,000 people were rendered homeless. The districts that were badly affected were Pondicherry (107 dead), and Karaikal (453 dead). In Pondicherry, Kariakal saw the most devastating affects and maximum number of deaths. Mostly fishermen in this region lost their lives and many were missing.

Andhra PradeshIn the state of Andhra Pradesh, the districts that were affected were Prakasam (35 dead), West Godavari (8 dead), Nellore (20 dead), Krishna (35 dead), Guntur (4 dead), and East Godavari (3 dead).

KeralaIn the state of Kerala, the districts that got affected were Alappuzha (32 dead), Kollam (131 dead), Ernakulam (5 dead). About 187 villages and 24.70 lakh people were severely affected. About 6,280 dwelling units were damaged.