Natural disasters can wreak havoc on the environment, causing significant damage to cities, towns, homes, and businesses. These naturally occurring events take many forms, including hurricanes, floods, earthquakes, and tornadoes. Among these, tsunamis stand out as some of the deadliest disasters, leaving immense destruction and loss of life in their wake.
Five tsunamis, in particular, are known as the deadliest in history, each marking a catastrophic event due to the sheer scale of death and destruction they caused.
What Causes a Tsunami?
This Article Includes
A tsunami is an enormous wave generated by a disturbance in the ocean. The most common cause is an earthquake, but volcanic eruptions and even human activities can also trigger these massive waves. Earthquakes happen when two plates of the Earth’s crust suddenly and violently move against each other. This can occur when one plate slides beneath the other or when two plates collide head-on. When this happens, the water above the disturbance is displaced, creating a wave. If the wave is large enough, it can turn into a tsunami. Volcanoes can also displace large volumes of water, creating similar waves.
Human-Triggered Tsunamis
Humans can also cause tsunamis, most often by detonating explosives underwater. These explosions generate waves that can develop into tsunamis. When these waves are large enough, they can cause widespread damage to coastal areas and even inland regions.
Now, let’s take a look at the worst tsunamis in history and what caused them.
Vajont Dam, Italy — Megatsunami
In northern Italy, the Vajont Dam stands as one of the tallest in the world, measuring 860 feet. Located in the Vajont River valley beneath Monte Toc, in the town of Erto e Casso, the dam was built between 1957 and 1960 by Società Adriatica di Elettricità (SADE). On October 9, 1963, during the initial filling of the lake, a landslide triggered a megatsunami that sent 50 million cubic meters of water over the dam in a wave that reached 820 feet high. This caused massive flooding and destruction in the Piave Valley below, wiping out several villages and towns and claiming the lives of around 1,900 to 2,500 people. Remarkably, most of the dam stayed intact, and two-thirds of the water remained behind it.
Vajont Dam Megatsunami (cont.)
The disaster occurred despite reports warning of the geologically unstable nature of Monte Toc, which were ignored by ENEL Green Power (ENEL) and the Italian government. Multiple warning signs were dismissed, and ENEL, unaware of the magnitude of the impending landslide, tried to prevent it by lowering the lake’s water level, just as the disaster struck.
Lituya Bay, Alaska — Megatsunami
In 1958, an earthquake in Lituya Bay, Alaska, triggered a tsunami with an astounding height of 1,720 feet, the highest ever recorded. The wave claimed the lives of five people, injured many others, and destroyed several homes. Among the casualties were two fishermen who perished in the bay after being swept up by the wave. Interestingly, a fishing boat captain and his seven-year-old son were hurled hundreds of feet into the air but survived with only minor injuries.
Yakutat, the only nearby permanent settlement, experienced damage to its bridges, docks, and oil lines. A cabin was destroyed when a wave knocked over a tower, and underwater cables from the Alaska Communication System were severed. Further damage was observed in Sitka and Pelican, where the tsunami destroyed forested areas along the shoreline, leaving only a few trees standing. The entire bay was flooded, leaving behind a 700-foot-long damage line still visible today from space.
Lituya Bay Megatsunami (cont.)
The megatsunami flooded the bay, leaving the shoreline barren, with no trees standing. It uprooted and swept away many trees, damaging the area in a way that can still be seen today.
Krakatoa 1883
The eruption of Krakatoa in 1883, located in the Sunda Strait between Java and Sumatra, culminated on August 27, destroying over 70% of the island and surrounding archipelago as it collapsed into a caldera. The eruption lasted from May 20 to October 21, 1883, and was one of the most destructive volcanic events in recorded history. The sound of the explosion was heard 1,930 miles away in Perth, Australia, and was audible in 50 countries worldwide.
The eruption and the resulting tsunamis are thought to have caused the deaths of at least 36,417 people. The tsunamis, triggered by the collapse of the eruption columns, shook ships as far as South Africa. Victims’ bodies were discovered floating in the ocean for months afterward. A tsunami taller than 150 feet devastated Merak.
Krakatoa (cont.)
The tsunamis resulted from the displacement of seawater as several cubic kilometers of material entered the ocean during the eruption. The explosion caused massive pyroclastic flows that led to the tsunamis, which were among the deadliest in history.
Tōhoku Earthquake and Tsunami
The 2011 Tōhoku Earthquake in Japan, the most powerful recorded earthquake in the country, sent powerful tsunami waves toward Miyako, possibly reaching heights of 133 feet. The waves traveled up to 6 miles inland at speeds of 435 mph in the Sendai region. Residents had only eight to ten minutes of warning, and more than a hundred evacuation points were destroyed. Rescue efforts were severely hampered by the tsunami’s snowfall and freezing temperatures.
Reports from 2015 indicated that 228,863 people were still living in temporary housing or had permanently relocated. Official statistics from 2021 showed 19,747 deaths, 6,242 injuries, and 2,556 people missing. The tsunami also caused meltdowns at the Fukushima Daiichi nuclear plant, releasing radioactive water and creating evacuation zones that affected hundreds of thousands of residents.
Tōhoku Earthquake and Tsunami (cont.)
The tsunami’s impact on the Fukushima nuclear power plant, with waves reaching heights of 13 to 14 meters, led to the most severe nuclear accident since the 1986 Chernobyl disaster. The incident was initially rated as a level five on the International Nuclear Event Scale (INES) but was later upgraded to level seven, the highest classification, along with Chernobyl.
Indian Ocean Earthquake and Tsunami
During the 2004 earthquake, the seabed suddenly shifted several meters, displacing vast amounts of water and triggering a tsunami that impacted the coasts of the Indian Ocean. This type of tsunami, known as a teletsunami, can travel long distances from its origin. Tsunamis typically behave differently in deep water, forming broad, low waves that are barely noticeable and harmless as they travel at speeds of 310 to 620 mph. When these waves reach shallow waters, close to coastlines, they slow down but increase in height, becoming destructive.
Indian Ocean Earthquake and Tsunami (cont.)
In Aceh, Indonesia, scientists discovered that the tsunami wave reached 80 feet when it hit the shore and 100 feet inland. The tsunami took anywhere from 15 minutes to 7 hours to reach different regions, with Sri Lanka and India’s east coast being hit 90 to 120 minutes after the initial wave. Thailand, despite being closer to the epicenter, was struck two hours later due to the shallow Andaman Sea.
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