Geophysical Phenomena

A tsunami refers to a series of ocean waves that sends surges of water, sometimes attaining heights of over 100 feet (30.5 meters), onto land. They approach coastlines with little or no warning signs, making them highly dangerous and deadly, hence often referred to as silent killers. An illustrative instance is the devastating 2004 Indian Ocean tsunami, which resulted in the loss of hundreds of thousands of lives and widespread destruction.

Triggers behind the Formation of Tsunamis:

• Earthquakes: Tsunamis are often triggered by underwater earthquakes. These seismic events can cause the seafloor to uplift or subside abruptly, displacing a large volume of water. For instance, the 2011 Tohoku earthquake in Japan generated a massive tsunami that reached heights of up to 133 feet (40.5 meters).
• Landslides: Submarine landslides, especially in coastal or underwater terrains, can displace substantial amounts of water and generate tsunamis. An example is the 1958 Lituya Bay landslide in Alaska, which created a tsunami that reached a height of approximately 1,720 feet (524 meters) – the tallest tsunami wave in recorded history.
• Volcanic Eruptions: Explosive volcanic eruptions occurring near or beneath the ocean can also induce tsunamis. When volcanic material, like ash and rock, plunges into the water, it displaces it, causing waves. The eruption of Krakatoa in 1883 generated a tsunami that killed tens of thousands of people across coastal regions in Indonesia.
• Faulting: Seafloor faulting can result in sudden vertical displacement of the seabed, displacing seawater and initiating a tsunami. The underwater Sanriku Fault off the eastern coast of Japan caused the 1933 Sanriku tsunami, which reached heights of up to 94 feet (28.7 meters).
• Upliftment of the Oceanic Bottom: In some cases, geological processes, such as the rapid upliftment of the oceanic bottom due to tectonic forces, can trigger tsunamis. An example is the 1946 tsunami in the Aleutian Islands, Alaska, caused by the upliftment of the seafloor.
• Plate Tectonics: Interactions between tectonic plates can create zones of subduction or collision, leading to powerful earthquakes and tsunamis. The subduction of the Indian Plate beneath the Burma Plate led to the devastating 2004 Indian Ocean tsunami.
• Anthropogenic Activities: Human activities, such as underwater nuclear tests or large-scale coastal engineering projects, have the potential to trigger tsunamis.

Devastating Impact of Tsunamis on the Coastal Regions:

• Loss of Life and Injury: Tsunamis can cause massive casualties as they inundate coastal areas with a wall of water, sweeping away people and causing severe injuries. For example, the 2004 Indian Ocean tsunami resulted in the tragic loss of about 2,30,000 lives across multiple countries, leaving countless others injured and traumatized.
• Displacement and Homelessness: Tsunamis can force people to flee their homes, leading to temporary or long-term displacement and homelessness. The 2004 Indian Ocean tsunami displaced approximately 1.7 million people from their homes.
• Economic Impact: Coastal regions often rely on industries such as fishing and tourism, which can be severely impacted by tsunamis, leading to economic downturns. Worldwide, since the beginning of the twenty-first century, 48 tsunamis have resulted in approximately $300 billion worth of economic losses.
• Destruction of Infrastructure: Tsunamis can destroy buildings, roads, bridges, and other critical infrastructure, disrupting the functioning of coastal communities.
  • For instance, the 2011 Fukushima nuclear accident due to Tohoku earthquake and tsunami. It resulted in grid failure and damaged nearly all of the power plant’s backup energy sources.
• Environmental Damage: Tsunamis can have long-lasting ecological impacts, such as damage to coastal ecosystems, contamination from debris and pollutants, and destruction of coral reefs.
  • In the aftermath of the 2004 tsunami in Indonesia, BAPPENAs (State Ministry of National Development Planning) estimated that 20 percent of seagrass beds, 30 percent of coral reefs, 25-35 percent of wetlands, and 50 percent of sandy beaches along the west coast were damaged.
• Radiation Hazard: Tsunamis can pose a radiation hazard when they damage nuclear power plants, potentially leading to radioactive leaks and contamination. For example, in March 2011, the Tohoku tsunami in Japan damaged the Fukushima Daiichi nuclear power plant, resulting in the release of radioactive materials into the environment.

To conclude, tsunamis, aptly referred to as “silent killers,” are a formidable force of nature capable of causing widespread devastation in coastal regions. As we confront the reality that globally, more than 700 million people live in low-lying coastal areas and Small Island Developing States, residing in vulnerable coastal areas, it is imperative that we continue to invest in preparedness, early warning systems, and sustainable coastal development to mitigate the potentially catastrophic effects of future tsunamis.