Tsunamis have been a relatively rare event in the Indian Ocean, at least in human memory, and have been quite prevalent in the Pacific. But every ocean has generated the scourges and left millions of people with scarred memories.
Fourteen years ago, such an event occurred, when an earthquake of magnitude 9.1 struck beneath the Indian Ocean near Sumatra, Indonesia and led to one of the most destructive disasters of all time. The earthquake triggered a series of waves, big, enormous waves, hence generating a massive tsunami that claimed more than 2 lac lives in different countries and became one of the deadliest natural disasters ever recorded.
The earthquake that generated the great Indian Ocean tsunami of 2004 is estimated to have released the energy of 23,000 Hiroshima-type atomic bombs, according to the U.S. Geological Survey (USGS). The violent movement of tectonic plates led to displacement of enormous amount of water and resulted in the largest rupture ever known to have been cause by an earthquake; 600 miles (1,000 kilometers) long, displacing the seafloor above by perhaps 10 yards (about 10 meters) horizontally and several yards vertically. That doesn’t sound like much, but the trillions of tons of rock that were moved along hundreds of miles caused the planet to shudder with the largest magnitude earthquake in 40 years.
The 2002 Sumatra earthquake that occurred on November 2, with a magnitude of 7.3 with an epicenter just north of Simeulue Island and caused three deaths, is regarded as a foreshock of the Indian Ocean earthquake that occurred in 2004.
The displacement of great volume of water along the rupture line, created one of nature’s most deadly phenomenon: a tsunami. A tsunami may be less than 30 centimeters in height on the surface of an ocean, which is why they are not noticed by sailors. But the powerful pulse of energy travels rapidly through the ocean at hundreds of miles per hour. Once a tsunami reaches shallow water near the coast it is slowed down. The top of the wave moves faster than the bottom, causing the sea to rise dramatically. The Indian Ocean tsunami caused waves as high as 50 feet (15 meters) in some places, according to news reports.
And within hours, waves radiating from the earthquake zone slammed into the coastline of 11 Indian Ocean countries.The Indian Ocean tsunami traveled as far as 3,000 miles to Africa and still arrived with sufficient force to kill people and destroy property.Indonesia, Sri Lanka, India, Thailand, the Maldives, Somalia, Myanmar, Malaysia, Seychelles were few of the majorly affected countries.
A great deal of humanitarian aid was needed because of the widespread damage to infrastructure, shortage of food and water, and economic losses. Epidemics were of special concern due to the high population density and tropical climate of the affected areas. The main concern of humanitarian and government agencies was to provide sanitation facilities and fresh drinking water to contain the spread of diseases such as cholera, diphtheria, dysentery, typhoid and hepatitis A and B.
There was also a great concern that the death toll could increase as disease and hunger spread. However, because of the initial quick response, this was minimized.
Beyond the heavy toll on human lives, the Indian Ocean earthquake caused an enormous environmental impact that is affecting and will continue to affect the regions for many years to come. It has been reported that severe damage has been inflicted on ecosystems such as mangroves, coral reefs, forests, coastal wetlands, vegetation, sand dunes and rock formations, animal and plant biodiversity and groundwater. In addition, the spread of solid and liquid waste and industrial chemicals, water pollution and the destruction of sewage collectors and treatment plants threaten the environment even further, in untold ways. The environmental impact will take a long time and significant resources to assess.
According to specialists, one of the major problems after the disaster was poisoning of the freshwater supplies and of the soil by saltwater infiltration and a deposit of a salt layer over the arable land. The Colombo-based International Water Management Institute monitored the effects of saltwater and concluded that, one and a half years after the event, the wells recovered to pre-tsunami drinking water quality.
EFFECT ON THE EARTH
The changes in the distribution of masses inside the Earth due to the earthquake led to several consequences. It displaced the North Pole by 2.5 cm. It also slightly changed the shape of the Earth, specifically by decreasing Earth’s oblateness by about one part in 10 billion, consequentially increasing Earth’s rotation a little and thus shortening the length of the day by 2.68 microseconds (NASA Press release).
National Geographic Society. “The Deadliest Tsunami in History?” 2005. Web Accessed May 28, 2018
Staff Writer. “Impact of Tsunamis on Ecosystems Archived 20 August 2008 at the Wayback Machine.” UN Atlas of the Oceans. Retrieved 28 May 2018.
UN upbeat on tsunami hunger aid”. BBC News. 9 January 2005. Retrieved 28 May 2018.
Helping restore the quality of drinking water after the tsunami. International Water Management Institute, 2010. Downloaded 28 February 2018.
Cook-Anderson, Gretchen; Beasley, Dolores (January 10, 2005). “NASA Details Earthquake Effects on the Earth”. National Aeronautics and Space Administration (press release).