Tsunamis | National Geographic

A tragic scene: entire cities flooded, entire towns inundated, an unending stream of floating debris—buildings, cars, people swept away in an unstoppable wave.

It’s a brutal reminder: tsunamis are dangerous and unpredictable. But what causes these giant waves, and what can be done to minimize their impact?

Tsunamis can strike with little warning because they’re usually triggered by a sudden displacement of ocean water, like volcanic eruptions, landslides, meteorites, or the most common culprit—earthquakes.

In the deep ocean, a typical tsunami wave is barely noticeable and poses little threat. But the waves can spread out thousands of miles, rolling across the ocean at speeds up to 600 mph. As the rolling water reaches the shoreline, the waves’ friction against the shallower floor slows it down and raises its height. By the time it reaches the shore, the wave can be as tall as 100 ft.

Unlike ordinary waves, a tsunami wave doesn’t crest and break. Instead, it moves forward like a solid wall of water that crashes over the coastline, obliterating almost everything in its path. And just when you think the danger is over, it recedes, dragging everything back to the ocean. Tsunamis have multiple waves, which can continue to hit the shore for several hours, causing even more destruction.

The word “tsunami” originates from Japan, a country that sits on a geographic location that makes it an easy target for these natural disasters. In 2011, it was struck by a tsunami that claimed nearly 16,000 lives. But the deadliest tsunami in history is believed to be the Indian Ocean Tsunami of 2004.

The US Geological Survey estimated that tsunami released the energy equivalent of 20–23,000 Hiroshima-type atomic bombs. An earthquake created an estimated 600-mile rupture on the ocean floor. This caused the tsunami to form and then travel at the speed of a jetliner, reaching over 11 countries, traveling over 3,000 miles, and killing more than 220,000 people.

Because they can strike so quickly with such deadly force, tsunami warning centers around the globe are on constant alert, monitoring underwater earthquakes large enough to trigger massive waves. Their ultimate goal is to alert vulnerable coastlines and give residents time to seek higher ground before a tsunami hits.

• inundated /ˈɪn.ʌn.deɪ.tɪd/ (adj) – Covered with water or overwhelmed.
  SYN: flooded, submerged
  Example: The town was inundated after the heavy rains.

• debris /dəˈbriː/ (n) – Pieces of something destroyed, like ruins or wreckage.
  SYN: rubble, remains
  Example: The tsunami left a trail of debris along the coastline.
• brutal /ˈbruː.t̬əl/ (adj) – Very harsh or cruel.
  SYN: harsh, savage
  Example: The disaster was a brutal reminder of nature’s power.
• minimize /ˈmɪn.ɪ.maɪz/ (v) – To make something as small or as unimportant as possible.
  SYN: reduce, lessen
  Example: We must take steps to minimize the impact of future tsunamis.
• displacement /dɪsˈpleɪs.mənt/ (n) – The act of being moved from a usual place.
  SYN: relocation, movement
  Example: Earthquakes often cause the displacement of large amounts of water.
• volcanic eruptions /vɒlˈkæn.ɪk ɪˈrʌp.ʃənz/ (n) – Explosions of lava and ash from a volcano.
  SYN: lava explosions, volcanic activity
  Example: Volcanic eruptions can lead to tsunamis in coastal regions.
• landslides /ˈlænd.slaɪdz/ (n) – Large amounts of earth and rock that slide down a slope.
  SYN: mudslides, avalanches
  Example: Heavy rains can trigger dangerous landslides.
• meteorites /ˈmiː.ti.ər.aɪts/ (n) – Rocks from space that hit the Earth’s surface.
  SYN: space rocks, asteroids
  Example: Rarely, meteorites can cause tsunamis if they land in the ocean.
• culprit /ˈkʌl.prɪt/ (n) – The cause of a problem or the guilty party.
  SYN: cause, offender
  Example: Earthquakes are often the main culprit behind tsunamis.
• pose little threat /pəʊz ˈlɪt.əl θret/ (v) – To present little danger.
  SYN: offer little danger, be harmless
  Example: At sea, tsunami waves usually pose little threat.
• shoreline /ˈʃɔːr.laɪn/ (n) – The edge of land next to a body of water.
  SYN: coast, seaside
  Example: The tsunami reached the shoreline within minutes.
• friction /ˈfrɪk.ʃən/ (n) – Resistance between two surfaces when moving.
  SYN: resistance, drag
  Example: The wave slowed due to friction with the ocean floor.
• crest /krest/ (n) – The top of a wave or mountain.
  SYN: peak, summit
  Example: The wave’s crest rose to nearly 100 feet.
• obliterating /əˈblɪt.ər.eɪ.tɪŋ/ (v) – Destroying completely.
  SYN: destroying, wiping out
  Example: The tsunami moved forward, obliterating everything in its path.
• recede /rɪˈsiːd/ (v) – To move back or away.
  SYN: withdraw, retreat
  Example: When the wave began to recede, it dragged debris with it.
• drag /dræɡ/ (v) – To pull something along with effort.
  SYN: pull, haul
  Example: The tsunami dragged everything into the sea.
• destruction /dɪˈstrʌk.ʃən/ (n) – The act of ruining or breaking something completely.
  SYN: ruin, devastation
  Example: The tsunami caused widespread destruction along the coast.
• geographic location /ˌdʒiː.əˈɡræf.ɪk ləʊˈkeɪ.ʃən/ (n) – A specific place on Earth.
  SYN: region, area
  Example: Japan’s geographic location makes it prone to tsunamis.
• equivalent of /ɪˈkwɪv.əl.ənt əv/ (n) – Something equal in value or meaning.
  SYN: equal to, comparable to
  Example: The tsunami’s energy was the equivalent of 20,000 atomic bombs.
• rupture /ˈrʌp.tʃər/ (n) – A break or tear in something.
  SYN: break, split
  Example: An earthquake caused a massive rupture on the ocean floor.
• jetliner /ˈdʒetˌlaɪ.nər/ (n) – A large airplane for passengers.
  SYN: aircraft, airplane
  Example: The wave moved at the speed of a jetliner.
• ultimate goal /ˈʌl.tɪ.mət ɡəʊl/ (n) – The final or main objective.
  SYN: final aim, main purpose
  Example: Their ultimate goal is to warn people in time.

• alert /əˈlɜːt/ (n) – A warning about danger.
  SYN: warning, alarm
  Example: Tsunami centers stay on constant alert.

Tsunamis are massive waves caused by earthquakes, volcanic eruptions, landslides, or meteorites. They are usually harmless at sea but become powerful and destructive as they approach the shore, wiping out everything in their path and pulling debris back into the ocean. Coastal areas, especially Japan, often experience these disasters, such as the 2004 Indian Ocean tsunami, which claimed over 220,000 lives. Therefore, warning centers constantly monitor and alert people in high-risk areas to evacuate in time.