Tsunami

A suggested lesson sequence

Use these stages at your own pace. Pause for students to sketch, compare observations or lead part of the demonstration.

01
Observe
Scrub the first source stage and explain water displacement, contrasting it with wind-driven surge. Continue to the separate propagation approximation and follow the prescribed wave packet.
Open Observe
02
Tinker
Read the same front’s speed in deep and shallow water. Use the metre-scale chart to compare amplitudes.
Open Tinker
03
Explain
How does decreasing water depth change the speed and height of a long wave approaching the coast?
Open Explain
04
Check
Choose an answer and explain your reasoning. Each question includes feedback.
Open Check

Rehearse with the model

The same scene and controls as the lab. Load it when you are ready; use Start projector for the full classroom view.

Before the lesson

Explain how seafloor displacement generates a tsunami and why its speed and height change as it enters shallow water.

Open the model before the lesson and choose a view that makes the important feature easy to see. Drag to rotate, and use the on-screen controls to change one variable at a time. The Controls panel explains the available keyboard shortcuts.

Pause the animation at a useful moment. Ask students what should happen next, then play it to test their explanation.

Guide the demonstration

Scrub the first source stage and explain water displacement, contrasting it with wind-driven surge. Continue to the separate propagation approximation and follow the prescribed wave packet.

Read the same front’s speed in deep and shallow water. Use the metre-scale chart to compare amplitudes.

Discuss a common misconception

“A tsunami and a storm surge are the same kind of coastal wave.” A tsunami is a sequence of long waves generated by rapid water displacement, such as seafloor movement or a landslide. Storm surge is an abnormal water-level rise driven mainly by storm winds and atmospheric pressure. Their causes, propagation and warning evidence differ.

Build the explanation

A tsunami has a long wavelength and travels faster in deeper water. As it crosses into shallower water, it slows and its amplitude can increase as energy is concentrated into a smaller depth.

Read the same front’s speed in deep and shallow water. Use the metre-scale chart to compare amplitudes.

This long-wave calculation ends offshore and excludes breaking, run-up and inundation on land.

Teaching notes

Distinguish a tsunami from astronomical tides and wind-driven storm surge, including the 1953 North Sea event.

Explain why a tsunami can have a small wave height in deep water and change greatly as it enters shallow water.

Connect coastal flooding to the generating process instead of identifying the hazard from water level alone.

Check understanding

Open Check for 4 questions. Ask students to explain their choice before revealing the answer.

Return to the opening photograph. Ask students to identify one visible feature and explain which part of the model helps account for it.

Look more closely

Use these observations to connect the vocabulary to features students can identify.

Shoaling

A breaking wave curls and foams along the coast at Porto Covo, Portugal. — A breaking wave at Porto Covo, Portugal. In shallow water a wave slows and steepens; its crest eventually breaks.

Read the definition

Storm surge

An aerial view of damaged buildings and washed-over land on the Bolivar Peninsula after Hurricane Ike. — Bolivar Peninsula, Texas, September 2008. NOAA documented coastal damage from Hurricane Ike's storm surge.