---
title: "Tsunamis"
description: "Know what a tsunami is: a very large, fast ocean wave caused by an earthquake or volcanic eruption under the sea, which can cause great damage when it reaches land"
canonical: https://lightmysky.com/learn/science/tsunamis-mt_Wu-ftkzoiE
source: https://lightmysky.com/learn/science/tsunamis-mt_Wu-ftkzoiE.md
retrieved: 2026-10-19
---

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# Tsunamis

Know what a tsunami is: a very large, fast ocean wave caused by an earthquake or volcanic eruption under the sea, which can cause great damage when it reaches land

Subject: Science · Area: Volcanoes & Earthquakes · Ages 7 to 9
Page: https://lightmysky.com/learn/science/tsunamis-mt_Wu-ftkzoiE

## Ready when they can

- Explain that a tsunami is caused by an earthquake or eruption under the sea
- State that tsunamis travel very fast across the ocean
- Describe the damage a tsunami can cause when it reaches the coast

## Lesson: Tsunamis

A tsunami is a giant, fast wave in the ocean. It is not caused by wind or storms. It starts when the sea floor suddenly jolts, often during a strong earthquake or an underwater volcano eruption. That jolt pushes a huge amount of water outward.

*(drawing: A tsunami in deep water can zoom along at about 500 miles per hour, much faster than a car speeding on the highway.)*

Far out at sea, a tsunami can look like a low, wide bump. Ships may not even notice it go by. But as it nears the coast, the water gets shallow. The wave slows down and grows much taller.

**Example.** One day, the ocean floor shakes hard during an earthquake far from shore. Minutes later, the sea pulls back strangely from the beach. Then a wall of water rushes in. It floods streets, knocks over cars, and damages buildings near the shore.

**Tip.** If people ever hear a tsunami warning, they move to higher ground right away. A tsunami can arrive faster than you expect.

**Recap.** A tsunami is a huge, fast wave caused by an earthquake or eruption under the sea, and it can badly damage the coast when it arrives.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Power of Eruptions](https://lightmysky.com/learn/science/power-of-eruptions-mt_BLQ2_OXPod)
- [What Is an Earthquake](https://lightmysky.com/learn/science/what-is-an-earthquake-mt_e29VrLfmYt)
- [Why Earthquakes Happen](https://lightmysky.com/learn/science/why-earthquakes-happen-mt_NVr4AhsvIq)
- [What Is a Volcano](https://lightmysky.com/learn/science/what-is-a-volcano-mt_S9SKah-yi_)

## Opens up

- [Earthquake-Resistant Design](https://lightmysky.com/learn/science/earthquake-resistant-design-mt_yDZbQODIwp)