Tsunami Speed
Lesson notes
Overview
In deep ocean a tsunami races along at jet speed because wave speed grows with the square root of depth. This topic is rated beginner and is number 8 of 98 in Earth & Space. Core ideas and first intuitions. No prior knowledge needed.
What you are seeing
The panel above shows a graph of the function. Each slider changes one parameter, so you can see exactly how the curve bends, shifts or stretches. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.
In depth
A tsunami is a wave created by a sudden displacement of the sea floor, as in an undersea earthquake. In water much shallower than its wavelength, a wave travels at v = √(g·d), so in the deep ocean, at 4,000 m, it moves at about 200 m/s, or 700 km/h, as fast as a jet, with a height of under a metre. As it reaches shallow water it slows, and the energy is compressed into a tall wave that can run far inland.
Reading the relationship
The expression "v = √(g·d)" is a compact summary of the idea. It uses the symbols v, g, d; name what each one stands for before you start. Notice that it contains a square root, so the result grows more slowly than the quantity inside it. Then use the sliders to see how changing one quantity changes the others.
A guided exploration
1. Set every slider to its middle value and note the shape of the curve. 2. Move one slider at a time and describe whether the curve shifts, stretches or turns. 3. Find the value where the behaviour changes sharply, then connect it to the formula.
Try this
Start by only moving one slider at a time. Say aloud what you expect, then check.
Common pitfalls
Earth and space systems work on very different scales of time and distance. Check which scale a number refers to before comparing it with another.
How it connects
It builds on “How Volcanoes Erupt”, the topic before it in Earth & Space. Once you are comfortable, continue with “The Layers of the Earth”.
Why it matters
Earth and space science helps us understand our planet, its climate and the wider universe.
Where you might use it
- Revising “Tsunami Speed” before a class, exam or certification
- Forecasting weather and understanding climate records and their uncertainty
- Planning for earthquakes, floods and other natural hazards in cities
- Interpreting satellite images, space missions and the age of rocks and stars
Frequently asked questions
What is Tsunami Speed?
In deep ocean a tsunami races along at jet speed because wave speed grows with the square root of depth. It is a beginner topic in Earth & Space.
How do I use the Tsunami Speed simulation?
The panel at the top shows a graph of the function. Each slider changes one parameter, so you can see exactly how the curve bends, shifts or stretches. Move the sliders one at a time, then press Space to pause the animation and look closer.
What does the formula mean?
The expression v = √(g·d) packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.
Who is this topic for?
Core ideas and first intuitions. No prior knowledge needed. If the quiz feels hard, reread the lesson notes and try the previous topic first.
What should I learn before this?
Start with “How Volcanoes Erupt”, the previous topic in Earth & Space. Each topic in a subject builds on the ones before it.
How do I track my progress?
Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.