Everyone has heard of tsunamis. We all know that it has to do with a large wave in the ocean, and usually when we hear about one, there is widespread panic because of its destructive and deadly capability.
According to Merriam-Webster dictionary, a tsunami is “a great sea wave produced especially by submarine earth movement or volcanic eruption. Its etymology lies in the Japanese language; the word is a combination of the Japanese “tsu”, meaning harbor, and “nami”, meaning wave.
Lesser known to non-meteorological experts, tsunamis can also occur in large lakes or other bodies of water.
2. What do scientists use to detect a tsunami?
The US Tsunami Warning System consists of earthquake detectors that are located on the ocean floor. Gauges and monitors were originally put in place in the mid 20th century to monitor seismic activity. These were originally located in the Pacific Ocean only, but have now been expanded into the Caribbean and the North Atlantic. Satellites are also used to detect impending tsunamis, as these devices can measure sudden changes in the sea levels on Earth, indicating the possibility of a tsunami.
3. What happens after a tsunami hits?
After a tsunami hits a shoreline, the initial wave (depending on its height) will virtually level everything that it comes in contact with, leaving behind soggy ruins. After the initial wave, there are often other waves that are just as large, and they slowly diminish over time. These can be just as destructive and often take survivors by surprise, as they believe the catastrophe has ended, only to be pummeled with after-effect waves.
4. What causes a tsunami?
Tsunamis are most often caused by a shift in the underwater tectonic plates of the Earth. This is called an earthquake. When an underwater earthquake takes place, the plates sometimes buckle and create a sort of underwater mountain ridge. This displaces an enormous amount of water, which is the beginning of the makings of a tsunami. In the middle of the ocean, the waves are non threatening, as there is no human life to destroy. However, the ocean floor is much less deep towards shorelines than it is in the middle of the ocean. As these waves travel to land, they become larger, forced upward as the ocean floor rises. Once they hit land they have momentum and they have grown exponentially from their beginnings. There is nowhere for them to go except in the direction their momentum leads. Once they hit land, they destroy everything in their path, but they are able to lose their momentum, and they no longer have the push of the ocean currents and ocean floor beneath them.
5. What kind of damage can a tsunami cause?
In addition to deaths, which typically number in the thousands when a tsunami hits, other damages are monetarily, environmentally and personally beyond devastating. Water is extremely powerful, and when a large tsunami hits land, it levels concrete buildings, trees, and everything in its path. Nothing is spared. Besides the human loss, the waves can devastate natural ecosystems and habitats that have formed over thousands of years, leaving behind sparse plant and animal life.
After the passing of a tsunami, survivors are at a great risk for pollution and disease. This is spread through unsanitary living conditions, dead bodies left undiscovered, and potential health hazards left behind by whatever was in the path of the wave.
6. List of the largest tsunamis on record:
5. Location: southern Chile
Date: May 22, 1960
Earthquake magnitude (cause of tsunami): 9.5 on the Richter scale
When the tsunami hit the southern Chilean coast on May 22, 1960, it immediately flooded 500 miles of the country’s coast. The wave caused flooding, mudslides, home damages, and $550 million (not adjusted for present day inflation) in damages. The total fatalities were estimated at around 3,000 lives. While this isn’t the largest number of lives lost during a tsunami, the toll was significant, and Chile spent years repairing what was lost that day.
4. Location: Messina, Italy
Date: December 28, 1908
Earthquake magnitude (cause of tsunami): 7.2 on the Richter scale
Before the tsunami even had a chance to hit the small Italian city of Messina on December 28th, the earthquake that originally caused the catastrophe destroyed much of the town due to its sheer magnitude. The resulting tsunami wave reached heights of 40 feet before the subsequent waves began to diminish in size. The result to the coastal town was vast. Two-thirds of the estimated 150,000 residents in the town, or 100,000 people died in the earthquake and tsunami. The city was left in ruins, a mess of stone rubble and destruction.
3. Location: Lisbon, Portugal
Date: November 1, 1755
Earthquake magnitude (cause of tsunami): 9 on the Richter scale
The Lisbon earthquake and resulting tsunami is one of the top three tsunamis of all time. On the morning of November 1 in 1755, Lisbon Portugalexperienced an enormous earthquake that tore their city into pieces. The horrible event continued for about ten minutes. When survivors thought it was all over, they were surprised to see an enormous tsunami reaching their shores. The waves reached almost 100 feet in height and caused even further damage. When all was finished, the death toll was estimated at 100,000 people. More than three quarters of the entire city was destroyed by the earthquake, tsunami and resulting fires that swept through the city for days afterward.
2. Location: Krakatau, Indonesia
Date: August 27, 1883
Cause: Volcanic eruption
On August 27, 1883, villages in Indonesia were devastated at first by one of the largest volcanic eruptions on record throughout the world. The eruption was reportedly heard as far as 2,500 milesaway, and the plume height was around 15 miles high. The Volcanic Explosivity Index registered the eruption as a 6, defined as being a colossal eruption. The tsunami that emerged from the volcano area reached the share of Indonesia shortly after the catastrophe began. Waves reached 140 feet high and completely flattened hundreds of villages, taking in excess of 35,000 lives.
1. Location: Indian Ocean
Date: December 26, 2004
Cause: Earthquake; 9.15 on the Richter scale
The most recent tsunami on record was also the most catastrophic. On December 26, 2010, an earthquake took place in the Indian Ocean, which reached the shores of nearby India, Indonesia, Sri Lanka and Thailand within a few hours. The tsunami affected the lives of people in twelve countries in total, and took an eventual death toll of 310,000 lives.
7. When is the tsunami season?
Unlike tropical storms, which have certain seasons, tsunamis can happen at any time. They are caused by seismic activity including earthquakes and volcanic eruptions, which are unpredictable and occur year–round. Because of this, there is no specific season during which tsunamis are most likely to be generated.
A tsunami, sometimes called a tsunami wave train, is a series of waves that are triggered by the sudden displacement of large volumes of sea water. Tsunamis usually occur in the ocean, but have been reported in lakes and rivers. Tsunamis occur frequently in Japan. Over the course of Japanese history, Japan has been struck by a major tsunami 195 times. As a result of the ability to displace very large volumes of water, and their ability to strike with great energy, tsunamis frequently devastate low-lying coastal regions.
8 .What Does the Word “Tsunami” Mean?
The term tsunami comes from the Japanese words “tsu,” which means harbour, and “nami” which means wave. Tsunamis are sometimes referred to as a tidal wave. However, this term has fallen out of use, particularly in the scientific community. The reason for this is because the generation of tsunamis is not related to the tides. Rather, the term “tidal wave” comes from the tsunami’s similar appearance to a very high tidal bore. Both produce very high waves that reach very far inland, however the damage done by a tsunami is much more extensive.
9. Tsunami Wavelengths and Amplitudes
Tsunamis have a small wave height, or amplitude, and very long wavelength. In the open ocean, tsunamis can be hundreds of miles long, but only a foot high. As a result, they often pass unnoticed by ships. Tsunamis grow in height as they reach shallow water. Tsunamis can occur at any tidal state. Even at low tide, tsunamis can still flood low-lying coastal areas.
Everyday wind waves have an average wavelength of 300 feet and an amplitude of six feet. In contrast, a tsunami in the open ocean can have a wavelength of 200 kilometres. Tsunamis in the open ocean travel at speeds upward of 500 miles per hour. Due to their high speed and the wave’s very low amplitude, it often only takes half an hour or less to complete a cycle. As a result, tsunamis are nearly impossible to detect in the open ocean without a tsunami warning system.
As a tsunami approaches the coast, the sea floor begins to rise and wave shoaling forces the wave to compress. It also slows the velocity of the wave to 50 miles an hour. The tsunami’s wave length compresses to 12 miles while its amplitude begins to increase, as a result, the tsunami becomes visible for the first time. Since the tsunami still has a very long wavelength, it may take several minutes for the tsunami to reach its full height. With the exception of the very largest tsunamis, most tsunamis do not break; rather they take the appearance of a fast moving tidal bore. It is for this reason that tsunamis are sometimes erroneously called tidal waves.
When the peak of the tsunami comes ashore, it triggers a temporary rise in sea level known as a run up. The run up is measured in meters above sealevel. A very large tsunami may come in multiple waves over a period of several hours. Additionally, the first wave that reaches shore may not be the largest and may not have the highest run up.
Approximately 80% of all tsunamis occur in the Pacific Ocean, however, tsunamis can occur in any large body of water.