What Causes Tsunamis: 4 Main Causes & Effects!

Something we have all thought about when surfing, Tsunamis. But what causes tsunamis to inflict such devastation across our world's oceans?

This article goes into what causes Tsunamis, the effect it has and what you can do before a tsunami to be safe.

What Causes Tsunamis 

Tsunamis are primarily caused by underwater disturbances such as earthquakes, volcanic eruptions, landslides, or extraterrestrial collisions, leading to the displacement of ocean water and the generation of powerful waves.

What is a Tsunami 

A tsunami is a series of powerful ocean waves, characterised by long wavelengths, triggered primarily by underwater disturbances like earthquakes, volcanic eruptions, or landslides. 

Tsunami waves can result in devastating coastal flooding upon reaching shallow waters.

4 Factors That Causes Tsunamis 

1. Earthquakes

Tsunamis often find their origin in powerful underwater earthquakes. 

When tectonic plates beneath the ocean floor abruptly shift, they displace enormous volumes of water, setting off a chain reaction that causes tsunami waves.

2. Landslides

Landslides, whether submarine or coastal, have the potential impact the environment that causes tsunamis. 

The sudden movement of large masses of sediment or rock into the ocean can disturb the water column, creating waves that propagate across the sea.

3. Volcanic Eruption

Volcanic eruptions, particularly those occurring beneath the ocean displaces water and violently causes tsunamis. 

The explosive release of gases and molten material can lead to the formation of tsunami waves that propagate outward from the eruption site.

4. Extraterrestrial Collision

In rare instances, extraterrestrial events such as meteor or asteroid impacts in the ocean which causes tsunamis. 

The immense energy released upon impact creates powerful shock waves that propagate through the water, producing tsunami waves with far-reaching consequences.

Geological Factors

Plate Tectonics

Plate tectonics, a fundamental geological concept, explains the dynamic movement of Earth's lithospheric plates. 

The interaction between these plates at plate boundaries can lead to various geological phenomena, including earthquakes and volcanic activity, which, in turn, causes tsunamis.

Ring of Fire

The Ring of Fire is a horseshoe-shaped zone encircling the Pacific Ocean, known for its high seismic and volcanic activity. 

Many tectonic plate boundaries within the Ring of Fire create conditions conducive to earthquakes and volcanic eruptions, making it a hotspot which causes tsunamis.


Subduction occurs when one tectonic plate slides beneath another, creating a subduction zone. These zones are often associated with intense geological activity, including powerful earthquakes and volcanic eruptions. 

Subduction zones can be key contributors to tsunamis due to the rapid displacement of water caused by seismic events.

Tsunami Movement

When one of these factors causes tsunamis, they exhibit unique movement characteristics that set them apart from regular ocean waves.

Speed of Tsunami Waves

Tsunami waves can travel at incredibly high speeds across the open ocean, often reaching speeds of up to 500 to 600 miles per hour (800 to 1000 kilometres per hour). 

Despite their swift pace, these waves can span vast distances, crossing entire ocean basins.

Deep-Water Phenomenon

In the open sea, tsunamis are characterised by long wavelengths and relatively low amplitudes, making them difficult to detect. 

Their subtle presence beneath the ocean surface goes unnoticed by ships, and their energy is distributed across a large water column.

Coastal Amplification

As tsunamis approach shallower coastal waters, their speed decreases, but their amplitude increases dramatically. 

This process, known as coastal amplification, causes the waves to grow in height, posing a significant threat to coastal communities.

Prolonged Activity

Tsunamis can exhibit prolonged activity, with multiple waves arriving over an extended period. 

The first wave may not necessarily be the largest, and subsequent waves can continue to impact coastlines, leading to extended periods of flooding and destruction.

Effects of Tsunamis

Tsunamis, with their immense energy and force, leave a profound impact on both humans and the environment.

Tsunami Effects on Humans

Tsunamis can cause widespread destruction, resulting in loss of life, injuries, and displacement of communities. 

The forceful inundation of coastal areas can lead to drowning, trauma, and infrastructure damage. 

The aftermath often involves significant humanitarian challenges, requiring rapid response and recovery efforts to address the needs of affected populations.

Tsunami Effects on the Environment

The environmental consequences of tsunamis extend beyond human settlements. 

Coastal ecosystems, including beaches, wetlands, and coral reefs, may experience substantial alterations. 

Sediment deposition, changes in water quality, and disruption to marine habitats can occur, impacting the delicate balance of coastal ecosystems.

Tsunami Safety

Ensuring the safety of individuals and communities in the face of a potential tsunami requires a combination of preparedness, awareness, and timely action.

1. Early Warning Systems

Establishing and maintaining robust early warning systems is critical, now often used to monitor tsunamis and rising sea level. These systems utilise a combination of seismic monitoring, ocean sensors, and communication networks to detect tsunami-generating events and provide timely alerts to coastal regions. Public education campaigns help communities understand the warning signals and the necessary response.

2. Evacuation Plans

Communities at risk of tsunamis must develop and regularly practise evacuation plans. Identifying safe evacuation routes and designated assembly points on higher ground is essential. Regular drills and community engagement contribute to effective responses in real-time emergencies.

3. Vertical Evacuation Structures

In areas with limited higher ground, the construction of vertical evacuation structures becomes crucial. These structures, often elevated buildings or specially designed towers, offer a refuge for individuals to seek safety above the potential inundation zone.

4. Community Preparedness

Community-wide preparedness involves education, drills, and collaboration. Building awareness of the tsunami risk, educating residents on evacuation procedures, and fostering a culture of readiness contribute to a resilient community capable of minimising the impact of these natural disasters.

Tsunami Forecasting

Tsunami forecasting involves a multi-faceted approach, combining seismic monitoring, oceanographic data analysis, and advanced modelling techniques. 

Seismometers strategically placed across tectonic plate boundaries detect and analyse seismic activity that may trigger a tsunami. 

Ocean buoys equipped with pressure sensors relay real-time data on sea level changes, aiding in the identification of tsunami waves in open waters. Sophisticated computer models assimilate this information to predict tsunami arrival times, wave heights, and potential impact areas along coastlines. 

Most Destructive Tsunamis in History

Throughout history, the world has witnessed tsunamis of staggering magnitude, leaving indelible marks of devastation in their wake.

1. Indian Ocean Tsunami (2004)

The Indian Ocean Tsunami of 2004 remains one of the deadliest natural disasters in recorded history. 

Triggered by a massive undersea earthquake off the coast of Sumatra, Indonesia, the tsunami radiated across the Indian Ocean, claiming over 230,000 lives in 14 countries. 

The impact underscored the need for international collaboration in early warning systems and disaster response.

What Causes Tsunamis

2. Tohoku-Oki Tsunami (2011)

The Tohoku-Oki earthquake off the coast of Japan in 2011 generated a colossal tsunami, causing widespread destruction and triggering a nuclear crisis. 

The tsunami's waves reached heights of over 130 feet (40 meters), leading to significant loss of life and extensive damage to infrastructure.

What Causes Tsunamis

3. Krakatoa Tsunami (1883)

The eruption of Krakatoa in 1883 unleashed a series of catastrophic tsunamis in the Sunda Strait, Indonesia. 

The colossal waves, some reaching heights of 120 feet (36 meters), devastated coastal communities and resulted in tens of thousands of fatalities.

What Causes Tsunamis

Summing It Up: What To Do Now

Nice! You are now well read on what causes tsunamis, make sure you check how at risk your surf break is to earthquakes. More importantly be safe!

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Frequently Asked Questions

Where do tsunamis happen the most?

Tsunamis occur most frequently in the Pacific Ocean's "Ring of Fire," including coasts of Japan, Indonesia, Philippines, New Zealand, and the Americas.

What caused the 2004 tsunami?

The 2004 Indian Ocean tsunami was triggered by a massive undersea earthquake off the coast of Sumatra, Indonesia.

Where do 90% of tsunamis occur?

About 90% of tsunamis occur in the Pacific Ocean's "Ring of Fire," encompassing Japan, Indonesia, the Philippines, and the Americas.

How many died in the 2004 tsunami?

Approximately 230,000 to 280,000 people died in the 2004 Indian Ocean tsunami.

How does a tsunami occur step by step?

Tsunamis start with an underwater disturbance like an earthquake, causing ocean floor displacement, wave propagation, shoaling near coasts, and eventual inundation.

How likely is a tsunami?

Tsunami likelihood depends on geological factors, with higher risk near tectonic plate boundaries; global probability varies, and early warning systems are crucial.

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