Tsunami Information: Worst Tsunamis in History

What is a Tsunami?

A tsunami is a series of waves caused by the displacement of large volumes of water, generally in an ocean, sea, or large lake. This can be due to seismic or volcanic activity, or even underwater explosions. Tsunamis are capable of traveling thousands of square kilometers across the ocean surface, with speeds of up to 800 kilometers per hour.

As the tsunami waves reach shallow depths, such as near coastlines, they slow down and can begin to grow significantly, with potential heights reaching up to 524 m (1,719 ft). Tsunamis can travel up to 620 miles (1,000 kilometers) away, reaching up to 0.6 miles (2km) or more inland, causing immense destruction in a matter of minutes. Despite the term ‘tidal wave’ being often used to refer to tsunamis, they are not actually caused by tides, but rather by large disturbances to the mass of water.

Worst Tsunamis in History Chart

Tsunami	Location	Date	Cause	Casualties
2004 Indian Ocean Tsunami	Indian Ocean	2004	Earthquake	227,000+
Messina Tsunami	Italy	1908	Earthquake-triggered landslide	123,000
Kanto Tsunami	Japan	1923	Earthquake	100,000
1854 Japan Tsunami	Japan	1854	Earthquake	80,000-100,000
1896 Sanriku Tsunami	Japan	1896	Earthquake	27,000
Valdivia Tsunami	Chile	1960	Earthquake	6,000+
1855 Edo Tsunami	Japan	1855	Earthquake	4,500-10,000

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What Factors Contribute to the Severity of a Tsunami?

1. Size of Tsunami

The size of a tsunami has a significant impact on its severity and the damage it can cause. The 2004 Indian Ocean tsunami that occurred off the coast of Sumatra was reported to be 50 meters or 164 feet tall, reaching up to five kilometers or three miles inland. This tsunami caused hundreds of thousands of deaths, thousands of people to be displaced from their homes, and billions of dollars in damage. Contrastingly, the 2011 Great East Japan Earthquake tsunami that occurred off the coast of Sanriku was reported to be 32 feet or 10 meters tall with an estimated magnitude of 7.6. While this tsunami caused around 19,747 deaths and 2,556 people reported missing, it also caused the Fukushima Daiichi nuclear disaster and billions of dollars in damage.

These examples show that the size of a tsunami is a major factor in determining its severity. In general, larger tsunamis are more destructive than smaller tsunamis in terms of the effect on people, property, and infrastructure.

2. Speed of Tsunami

The speed of a tsunami can greatly affect its severity. Tsunamis form a low, broad hump in deep ocean water that moves at speeds of up to 620 mph and can be barely perceptible and harmless. However, when the tsunami reaches shallow water close to the coastlines, its speed slows down to tens of kilometers per hour, which causes the waves to become massively destructive with much greater impact. This was seen in the 2004 Indian Ocean tsunami, where the waves grew to 80 feet tall when they hit the shore and 100 feet inland. The tsunami was able to cause such great destruction due to its speed, as it took between 15 minutes to 7 hours to reach the coast. If a tsunami moves at a faster speed than usual, it is more likely to cause more destruction and a higher loss of life.

3. Depth of Tsunami

The depth of a tsunami can have a major effect on its severity. The 2004 Indian Ocean tsunami was around 30 km deep and caused massive destruction, with an estimated 230,000 people dead and US$10b in damages. The 2011 Great East Japan Earthquake had a depth of around 10 km and caused the Fukushima Daiichi nuclear disaster, in addition to thousands of deaths and billions of dollars in damages. The deeper a tsunami is, the more energy it can accumulate, making it stronger and more destructive. Deep tsunamis are also more likely to cause vertical movement of the seabed, which can lead to even greater wave heights and devastation when it reaches shore.

4. Shoreline Impact

5. Type of Tsunami

Tsunamis can be classified into four main types based on the factors that cause them: Earthquake-induced tsunamis, Volcanic-induced tsunamis, Landslide-induced tsunamis, and Meteorite impact-induced tsunamis.

Earthquake-induced tsunamis are the most common form of tsunami and occur when a large earthquake, typically measuring over 7.0 magnitude on the Richter scale, occurs underwater. These earthquakes can cause the displacement of large volumes of water, which then form powerful waves. The severity of these tsunamis is largely determined by the size of the earthquake, the depth of the water, and the distance from the epicenter of the earthquake.

Volcanic-induced tsunamis occur when a large volcano erupts under the ocean or other bodies of water, such as a lake. These eruptions can cause large volumes of water to be displaced and form dangerous waves. The severity of these tsunamis is determined by the size of the eruption, the depth of the water, and the distance from the eruption site.

Landslide-induced tsunamis are caused when a large amount of earth and debris slides into the ocean or other bodies of water. These landslides can cause the displacement of large volumes of water, resulting in tsunamis. The severity of these tsunamis is determined by the size and speed of the landslide, the depth of the water, and the distance from the landslide site.

Meteorite impact-induced tsunamis occur when a large meteorite or asteroid impacts the ocean or another body of water. These impacts can cause large volumes of water to be displaced, resulting in powerful waves. The severity of these tsunamis is determined by the size of the impact, the depth of the water, and the distance from the impact site.

6. Consequence of Tsunami

The consequences of a tsunami can be devastating and far-reaching. In areas close to the epicenter of the tsunami, the destruction can be catastrophic, with destruction of buildings, infrastructure, and even entire villages. People can be injured, killed, and displaced. Coastal communities can be flooded, leading to major destruction of property and the environment. Further away from the epicenter, a tsunami can cause major flooding and destruction of marine life. It can also cause massive destruction of coral reefs and marine habitats. The destruction of coastal cities and towns can also lead to a major economic loss, with businesses and livelihoods impacted. There can also be long-term impacts, such as the destruction of habitats and wildlife, destruction of ecosystems, and destruction or damage to ports and infrastructure. Lastly, a tsunami can cause psychological trauma, with the destruction of communities and the displacement of people leading to feelings of grief, loss, and despair.

7. Earthquake Magnitude

The magnitude of an earthquake is directly related to the severity of the tsunami it can generate. The higher the magnitude of the earthquake, the larger the resulting tsunami waves will be, and the more destruction they are likely to cause. For instance, the 2011 Tohoku earthquake in Japan had a magnitude of 9.0, and the resulting tsunami waves were measured to be at least 6.6 feet high, leading to the destruction of entire towns and cities and the loss of thousands of lives. Similarly, the 2010 Haiti earthquake had a magnitude of 7.0, and the resulting tsunami waves were averaged to be about 10 feet high, causing a huge loss of life and destruction of homes. The 1707 Hoei earthquake in Japan had a magnitude of 8.4 and generated sea waves as high as 25m, damaging nearly 30,000 buildings and resulting in the loss of 30,000 lives. Thus, it is clear that the magnitude of an earthquake is an important factor in determining the severity of the tsunami it can cause.

8. Tsunami WARNING SYSTEM

A tsunami warning system is a network of monitoring and communication systems designed to detect tsunamis and provide timely warning to coastal populations of a potential tsunami threat. The system is designed to detect seismic activity that could potentially generate a tsunami, and then alert affected coastal populations of the potential threat so they can take appropriate action. The warning system is effective in reducing the potential damage and loss of life caused by a tsunami, as it provides the necessary time for people to evacuate and take shelter before the tsunami arrives. The warning system also helps to inform government agencies, allowing them to coordinate an effective response to the tsunami by dispatching emergency services and rescue operations.

9. Seismic Activity

Seismic activity is an important factor that affects the severity of a tsunami. When an earthquake occurs at sea, the displacement of the sea floor can cause massive waves to form, resulting in a tsunami. The larger the earthquake, the greater the displacement of the sea floor, leading to larger and more destructive tsunamis. Earthquakes of magnitude 8.8, 8.4, and 9.0 have caused devastating tsunamis that destroyed coastal towns, killed thousands of people, and caused billions of dollars in damage. The magnitude 9.1 earthquake off the coast of Sumatra caused a tsunami that was as tall as 50 m, reaching 5 km inland and resulting in 230,000 deaths.

10. Coastline Geography

The severity of a tsunami is directly related to the geography of a coastline. Factors that can affect the severity of a tsunami include the angle and profile of the coast, the size and shape of bays and harbors, the distance to the epicenter of the tsunami, the size of the tsunami wave, and the underwater topography. A coastline with a gentle slope surrounded by shallow water will be more vulnerable to tsunami damage than a coastline with a steep slope surrounded by deep water. Similarly, a coastline with small bays or harbors will be more vulnerable than one with larger ones. The distance to the epicenter of the tsunami is also important, as a tsunami will lose energy as it travels further away. Finally, the underwater topography can play a role in tsunami severity, as topography on the seafloor can increase or decrease the size of the tsunami wave.

For example, the island of La Palma in the Canaries has been the source of much talk as an ideal location for a landslide-induced megatsunami. Some scientists believe a future eruption of the island’s Cumbre Vieja volcano may cause its western flank to collapse, resulting in a wave large enough to engulf every port on the east coast of the United States. The size and shape of the bays, the distance to the epicenter of the tsunami, and the underwater topography all contribute to the potential severity of this future event.

The 10 Worst Tsunamis in History

1. Krakatoa Eruption and Tsunami — May 20th, 1883

The Krakatoa eruption and tsunami of 1883 were one of the most destructive and deadly natural disasters in history. The eruption of Krakatoa, an Indonesian volcano located between Java and Sumatra, occurred in four stages from May 20th to October 21st, 1883. The explosions from the volcano were heard up to 1,900 miles away in Western Australia and the sound wave traveled seven times worldwide. This catastrophic event resulted in thousands of deaths, destruction of Krakatoa, and a volcanic winter.

The violent eruptions of the Krakatau caldera volcano created multiple waves as high as 37 m that demolished the towns of Anjer and Merak. The ensuing tsunami, with waves as high as 150 feet tall, was felt as far away as South Africa and is said to have killed over 40,000 people in total. It destroyed 70% of the island and its surrounding archipelago and caused massive destruction of roads, railways, and nuclear reactors in Japan, resulting in additional evacuations within the Fukushima Prefecture.

The enormity of the destruction and the number of deaths caused by the Krakatoa eruption and tsunami make it one of the worst tsunamis in history. This event serves as a stark reminder of the devastation that natural disasters can bring.

2. Ambon Island, Indonesia // 328 Feet

The Ambon Island tsunami was a devastating natural disaster that occurred in 1674, resulting from an earthquake in the Maluku Islands in the Banda Sea. The peak height of the tsunami at Hitu Peninsula’s coastal hills was around 328 feet, indicating the sheer power of the natural forces unleashed by the earthquake. This makes it one of the largest tsunamis on record.

3. Lisbon, Portugal – 1 November 1755

The Lisbon, Portugal tsunami of 1755 was a devastating event that killed thousands of people and caused wide-spread destruction throughout the region. This double disaster was caused by a massive earthquake that had an epicenter in the Atlantic Ocean about 200 km off the coast of Cape St. Vincent in southern Portugal. Estimated to be between 8.5 and 9.0 on the Richter scale, the earthquake spawned a series of three huge waves that were up to 66 feet high, striking Portugal, Spain and Morocco. The waves also caused wide-ranging fires that further devastated the cities and towns, leading to an estimated 40,000 to 50,000 deaths.

This devastating tsunami is considered one of the worst in history due to its magnitude and the wide-scale destruction and loss of life it caused. The tsunami’s effects could be felt as far away as North Africa and islands across the Atlantic. The earthquake and resulting disasters also inspired European enlightenment philosophers, and led to the birth of seismology and modern earthquake engineering.

4. Krakatau, Indonesia – 27 August 1883

The Krakatau tsunami in Indonesia in 1883 had a maximum height of 150 feet (46 meters) and killed an estimated 40,000 people in the Indonesian Islands of western Java and southern Sumatra. In addition, the tsunami was recorded as far away as South Africa and is believed to have had an overall regional impact. The earthquake that caused the eruption was measured to be a 7.2 on the Richter scale.

5. Enshunada Sea, Japan – 20 September

The Enshunada Sea tsunami of December 7, 2012 is one of the worst natural disasters in history. It was an extremely powerful and destructive tsunami that originated from an earthquake measuring 9.0 on the Richter Scale that struck off the coast of Ishinomaki, Miyagi Province in Japan. The tsunami had a wave height of up to 40.5 meters, and it swept away entire villages and caused extensive damage to many coastal areas. It is considered one of the most destructive and deadly tsunamis in history due to the sheer power and magnitude of the wave and its ability to cause immense destruction in a very short period of time. The tsunami claimed the lives of nearly 16,000 people and caused an estimated $360 billion in economic damage. The tsunami was also responsible for the release of radioactive material from the Fukushima Daiichi Nuclear Power Plant, which contributed to the long-term environmental damage that was caused by the disaster. The Enshunada Sea tsunami is one of the worst tsunamis in history due to its destructive force and the devastating impact it had on Japan and the surrounding region.

6. Lituya Bay, Alaska // 1720 Feet

The Lituya Bay, Alaska tsunami was reported to be 1,720 feet tall, making it the tallest ever recorded. The megatsunami was caused by a 7.8 magnitude earthquake that struck the Fairweather fault, dislodging 90 million tons of rock into the bay. The steep walls of Lituya Bay and its proximity to the Fairweather fault line create the perfect conditions for such a destructive wave. The wave caused millions of trees to be destroyed and flooded the entire bay. It left a 700-foot-long damage line around its perimeter, which can still be seen from space today.

7. Mount St. Helens, Washington // 820 Feet

The Mount St. Helens tsunami in Washington had a height of up to 82 feet (25 meters). The landslide displacement caused an 820-foot tsunami, the third-largest in history, which crashed into the side of Mount Margaret before splashing back down into the basin below.

8. Northern Chile – 13 August 1868

The Northern Chile tsunami of 1868 is considered one of the worst tsunamis in history due to its magnitude, impact, and destruction. The tsunami was caused by a series of two powerful earthquakes with an estimated magnitude of 8.5 off the coast of Arica, Peru (now Chile). The resulting seismic waves caused immense damage and destruction, with waves reaching up to 21 metres in height and lasting for two to three days. The tsunami caused 25,000 casualties and an estimated damage of US$300 million along the Peru-Chile coast. Furthermore, the waves were felt by tide gauges in places as far away as Sydney, Australia. This is evidence of the devastating impact of the Northern Chile tsunami, making it one of the worst tsunamis in history.

9. Ryuku Islands, Japan – 24 April 1771

The Ryuku Islands, Japan, tsunami in 1996 was one of the most devastating tsunamis in Japanese history. It was caused by a magnitude 7.6 earthquake and resulted in two tsunamis that destroyed up to 9,000 homes and took at least 22,000 lives. It broke the record height at the time, reaching 125 feet or around 38 meters.

The force of the tsunami was so great that it removed all trees and vegetation from a height of 1,720 feet (520 m) above sea level, which was a much larger scale than ordinary tsunamis and led to the creation of the new category of megatsunamis. The waves spread across the whole Pacific Ocean and reached as far as Hilo, Hawaii, where the highest wave was measured at around 10.7 m (35 ft).

This tsunami was much more destructive than past tsunamis in the region, such as the Yaeyama Great Earthquake of 1771 and the 1952 Severo-Kurilsk tsunami in the Kuril Islands, USSR, which killed 10,000 and 2,336 people respectively. The 1960 Valdivia earthquake, which generated one of the most destructive tsunamis of the 20th century, was also less destructive than the Ryuku Islands’ tsunami as it only reached 25 metres (82 ft) in height and resulted in 61 deaths in Hilo, Hawaii.

10. Ise Bay, Japan – 18 January 1586

The Ise Bay Tsunami of 1586 is one of the worst tsunamis in history due to the immense destruction it caused. The earthquake that caused the tsunami is estimated to have been a magnitude 8.2 and the waves rose to a height of 6m, resulting in severe damage to a number of towns. The town of Nagahama experienced an outbreak of fire as the earthquake first occurred, destroying half the city, while Lake Biwa surged over the town, leaving no trace except for the castle. In total, the tsunami caused more than 8000 deaths and a great amount of damage. This devastation was immense for the time, and makes the Ise Bay Tsunami one of the worst tsunamis in history.

How to Prepare for a Tsunami?

1. Know the Warning Signs of a Tsunami

Tsunamis are one of the most destructive and devastating natural disasters and can occur suddenly with little or no warning. To be prepared for a tsunami, it is essential to be familiar with the warning signs and understand how to prepare for them.

The main warning signs of a tsunami are: an unusually strong or long earthquake, a loud roar from the ocean, a rapid rise or fall of the sea level, and water receding far from shore. Other signs can be abnormal ocean currents, floating debris, and strange behavior of ocean animals.

If you observe any of these warning signs, get to higher ground immediately and do not wait for an official warning. Make sure to keep yourself and your family safe and evacuate the area if necessary. Move to higher ground to avoid the tsunami and be prepared to stay there for several days.

It is also important to be aware of the local tsunami warning systems, if there are any. Be sure to have an emergency plan that includes an evacuation route and a safe place to go if a tsunami does occur. Have a kit with basic supplies such as food, water, and a first-aid kit. Make sure to keep the kit up-to-date and have an extra set of clothes, an extra pair of shoes, a flashlight, a radio, and a whistle in case of emergency.

Staying informed and understanding the warning signs of a tsunami can help you and your family be prepared in the event of a disaster. Make sure to stay alert and evacuate when necessary.

2. Understand the Risks of Your Area

When preparing for a tsunami in an area, it is important to consider the various risks associated. These risks include the potential for an earthquake, landslide, or volcano eruption in the area, as well as the possible receding of the tide or any other changes in the ocean. Additionally, it is important to consider the distance from the shoreline to higher ground and the risk of flooding, as well as the presence of any structures such as hotels and businesses in the tsunami risk zone. It is also important to consider the potential for disruption of communication, transportation, and electricity in the area and the need for evacuation routes. Finally, it is important to have an understanding of the population demographics in the area and the potential for an increase in deaths or injuries in the event of a tsunami.

3. Prepare a Tsunami Emergency Kit

A tsunami emergency kit should include items that can help keep you safe and comfortable during and after a tsunami. This could include:

• Non-perishable food and water: Keep a few days’ worth of food and water on hand, as well as supplies to purify water if necessary.
• Battery-powered radio: A radio will keep you informed of emergency updates.
• Flashlights and extra batteries: Have multiple flashlights and extra batteries to help you navigate in the dark.
• First-aid supplies: A first-aid kit should contain bandages, antiseptic cream, gauze, scissors, and other items.
• Medication: Make sure to pack any necessary medications.
• Extra clothing and blankets: Have warm clothing and blankets on hand, as well as rain gear.
• Important documents: Photos and copies of important documents such as identification cards, passports, and financial information should be stored in a waterproof container.
• Cash: Have some cash in case ATMs are not functioning.
• Critical phone numbers: Have a list of important phone numbers and contact information of family and friends.
• Pet supplies: If you have pets, make sure to pack food and supplies for them as well.
• Emergency tools: A Swiss-army knife, can opener, and other tools can be helpful in an emergency.

4. Know How to Evacuate Quickly

1. In the event of an earthquake, look for signs like the one in the reference image above.
2. Immediately evacuate the area. Move to higher ground or a higher elevation.
3. Do not wait for official warnings or instructions from authorities.
4. Move away from the coast as quickly as possible.
5. Leave your belongings and only take necessary items such as identification and medication.
6. Follow instructions given by authorities such as shelter in place or find higher ground.
7. Stay away from port and river areas that could be at risk of flooding.
8. If time allows, call your family and friends to let them know you are safe.

5. Have a Plan for Family Members

Families should prepare for a tsunami by taking the following steps:

1. Research the local tsunami risk and evacuation plan. Contact local emergency management offices and become familiar with the risk of tsunamis in your area and the evacuation plan in the event of a tsunami.
2. Identify a safe location. Determine a location in your area that is safe from the effects of a tsunami, such as high ground, a sturdy building, or an interior room on the top floor of a multi-story building.
3. Make an emergency kit. Gather essential supplies, such as food, water, flashlights, and a first aid kit, and store them in a waterproof container.
4. Have an evacuation plan. Have a plan for where to go in the event of an evacuation, such as an emergency shelter, friend or family member’s house, or a designated meeting area.
5. Practice the evacuation plan. Practice evacuating to the safe location with your family and make sure everyone knows the plan and what to do in the event of a tsunami.
6. Monitor weather conditions. Be aware of weather conditions in your area and listen to news and weather broadcasts for updates on possible tsunamis.

By following these steps, families can take the necessary steps to be prepared for a tsunami.

6. Make Sure Your Home is Tsunami-Proof

How can you make your home tsunami-proof?

1. Know the risks in your area. Research the tsunami history in your area and the likelihood of a tsunami occurring.
2. Make sure your home is built on high ground. If you’re in an area that may experience a tsunami, it is important to make sure your home is built on ground high enough to avoid flooding.
3. Install flood doors and windows. Make sure your home is equipped with flood doors and windows to protect it from floodwaters.
4. Elevate your home. Elevating your home can help protect it from flooding and damage in the event of a tsunami.
5. Install an alarm system. Installing an alarm system can help you be aware of incoming tsunamis and evacuate when necessary.
6. Create an evacuation plan. Have an evacuation plan ready in case a tsunami warning is issued and you need to evacuate quickly.
7. Plan for the aftermath. Have plans in place to help you, your family, and your property in the aftermath of a tsunami.

7. Check the Tide Gauge for Warnings

8. Pay Attention to the News for Tsunami Alerts

Paying attention to tsunami alerts can help prepare for a tsunami by providing early warning of an impending danger. By recognizing the warning signs and knowing what to do in the event of a tsunami, people can better protect themselves and their families. People should be aware of the potential of tsunamis in areas prone to them, such as the west coast of the United States and Japan, and should know the evacuation routes to take should a tsunami occur. Oceanographers and seismologists are also working to improve prevention methods for tsunamis, including automated systems and early warning systems. By being aware of the potential dangers and having the proper planning and preparation in place, people can be better prepared to handle a tsunami.

9. Learn Tsunami Safety Techniques

Tsunamis are one of the most devastating natural disasters and can have major impacts on coastal cities around the world. To protect yourself from a potential tsunami it is important to understand the warning signs and safety techniques that can be learned.

Some safety techniques that can be learned include:

1. Become familiar with local tsunami warning systems and signs. This can include automated systems as well as evacuation routes.
2. Pay attention to the tide and receding shoreline as this can be an indication of a potential tsunami.
3. Consider creating an evacuation plan that includes an escape route and a safe place to meet.
4. Stay informed of the latest tsunami warnings and forecast by monitoring local news and weather reports.
5. If you receive a warning or believe a tsunami is imminent, evacuate immediately.
6. When the wave is approaching, seek higher ground or a tall structure.
7. Keep away from the beach and low-lying coastal areas.
8. If you are in a boat, head for the open sea.
9. If you are driving, get as far away from the coast as possible.
10. Remain aware of aftershock warnings and pay attention to the tide.

By learning these safety techniques and understanding the warning signs of a potential tsunami, you can help ensure your safety in the event of a natural disaster.

10. Have an Emergency Supply Kit for Emergencies

An Emergency Supply Kit is an essential item to have in the event of a tsunami. It contains important items such as food, water, first-aid supplies, flashlights, battery-powered radio, and other items that can help you survive. Having an Emergency Supply Kit ready in advance can help you and your family survive in the event of a tsunami. It can also save valuable time in the event of an emergency because you won’t have to rummage around looking for these essential items. The kit should also be tailored to the needs of your family and should include items that can provide comfort and peace of mind such as additional clothes, blankets, and toys for children. Taking the time to prepare an Emergency Supply Kit ahead of time can help save lives in the event of a life-threatening tsunami.

Consider purchasing the following items to help keep yourself, your property, and your family safe during a tsunami: