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Tsunami

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Why this lesson, and why the 3D

Tsunami is a fifteen-minute projector lesson, not a homework packet and not a film with a quiz bolted on. Put this hook on the board before you dim the lights: Seafloor slip lifts a water column. In deep water the wave is fast and low. At the coast it stands up. By the end of the slot a pupil should be able to play seafloor slip to a coastal wave. Curriculum tags in the header (GCSE; NGSS MS-ESS3-2) are filters, not a flag. The room is worldwide; SI first; International English. Ages on the card (GCSE, NGSS MS, HS Earth Sci) are a suggested band, not a gate.

A tsunami is a long-period wave from a sudden displacement of the water column, most often seafloor slip on a megathrust. Cascadia is the North American drill: Juan de Fuca under North America, a 1700 wave written in Japanese records and in drowned coastal forests. Schools on that coast practise a vertical evacuation for a reason. Hawaii feels distant Pacific tsunamis; Iceland’s ridge is usually the wrong machine. San Andreas is mostly strike-slip: it shakes, it does not typically lift a whole water column. Katrina and Sandy pushed water by wind and pressure — storm surge, a different hazard that still floods a city. Holderness and the 1953 North Sea flood are UK surge and wave attack, not a megathrust. GCSE and NGSS both need that split: displacement wave versus wind sea versus tide. Do not call a UK gale a tsunami. Do not call a hurricane a tsunami. The physics is a lifted column, a fast low wave at sea, a tall slow wave at the coast.

The 3D is a named, inspectable object. Click the part, not a caption. If the model will not spin, the Why panel still carries the mechanism, the two photographs, and the film. Do not apologise for the model. Drive it. A silent spin teaches a screensaver. A named mesh that changes under a slider teaches the process.

Fifteen minutes on the projector

Play the seafloor slip. The water column lifts. The wave races. In deep water it is fast and low, often unnoticed at sea. Shallow water: slower, taller. Shoaling: energy in a shallower, slower water column. A tsunami is not a wind storm surge. Surge is wind and pressure. Tsunami is displacement. That is the misconception. Do not call the 1953 North Sea flood a tsunami. Cascadia drills are this lab. Holderness is a different wave. Sandy is surge, not tsunami. Contrast them once. Green’s law is the story, not a formula dump. Finish in Check.

Open the lab full screen (F). Labels on (L). Speak the first step before you touch a slider: Slip. The column lifts. Then the second: The wave races. Amplitude small at sea. Then the third: Shallow water: slower, taller.

Time, labels, and T (true scale) are the whole desk. Play walks the process; T removes the vertical lie where one was drawn. Space plays; arrows nudge time; R resets. Parameters the URL can remember: t, labels, true scale. If you only have eight minutes, skip the last step and finish in Check. Projector layout (P) is for the back row: one idea, large type, the model still live.

Play from the start. The seafloor block lifts; the water column follows. Watch the pulse race across deep water: fast and low. As it reaches the shelf it slows and stands up — shoaling. Labels: Seafloor slip, Deep = fast and low, Shoaling. Orbit between the profile and the plan if both are in view. Pause at sea and ask whether a ship would feel a wall; it would not. Pause at the coast and name why it grew. Contrast once with surge: Sandy is wind and pressure, not this slip. Cascadia drills are this lab. Then sit down.

The in-site film is “How tsunamis work — Alex Gendler” (TED-Ed, about 4 min, TED-Ed on YouTube. Standard YouTube licence. Educational embed, autoplay off.). Autoplay is off. Play one minute if you need a second voice; do not let the film eat the slot. The 3D still has to move under your hand.

What the third row will get wrong

You will hear the misconception before you have finished the first sentence. Write the false claim on the board and leave it there until the model has contradicted it. Do not skip this. A fluent pupil can recite the hook and still believe the false sentence.

“A tsunami is a wind storm surge.” — no. Different machine. Surge is wind and pressure. Tsunami is displacement.

“A tsunami is a 30 m wall everywhere, including mid-ocean.” — no. In deep water it is fast and low. It stands up at the coast.

“The 1953 North Sea flood was a tsunami.” — no. It was a storm surge. Wrong machine.

Pitfalls to keep in your pocket: Calling 1953 North Sea a tsunami. A mid-ocean wall in every drawing. Surge and tsunami as synonyms. Tide and tsunami mixed because both change water level. Do not let a pupil leave thinking the 3D is a photograph. It is a teaching model. Where vertical exaggeration exists, T collapses it and the caption says so. A labelled lie of scale is honest. An unlabelled one is a cartoon.

Two places, not a slogan

Start with slip. A patch of seafloor jumps up (or down). The whole water column above it moves. That is the source, not a gust and not the Moon. In deep water the wavelength is huge, the amplitude is small, and the speed is high — ships may not notice. Energy is in the column, not in a wind-chopped surface. As the wave enters shallow water it shoals: speed falls roughly with the square root of depth, wavelength shortens, amplitude grows. Green’s law is that story, not a formula dump for KS3. The wave that was a ripple at sea can stand up at a harbour. Bay shape, shelf width and drawdown before the crest all matter; this lab is the cross-section, not a run-up atlas. A storm surge is wind piled against a coast plus a pressure set-up. A tide is gravity of Moon and Sun. A tsunami is displacement. Three water-level machines. Cascadia is the first. Katrina and Sandy are the second. Do not file 1953 under the first. Holderness till cliffs are ordinary storm waves plus a budget, another lab. Keep the verbs: lift, race, shoal, flood.

The first place to land is Cascadia. The second is Surge is not tsunami. Same process, different rock or climate. If a pupil can only name one place, they have a postcard, not a mechanism. Atlas entries for those names are a click from the case list; send them back to the lab with one sentence they can say in Check.

Do not flatten the comparison into “this country versus that country.” Name the landform. Holderness is till, not chalk. Hawaii is a hotspot, not an island arc. Yosemite is a glacial trough, not a river canyon. The 3D is allowed to be schematic; the place names are not allowed to be sloppy.

Figures and the film

Field photograph: A tsunami’s run-up on a coast. A tsunami’s run-up on a coast. Long-period wave from a sudden water displacement, often seafloor slip. Source: Wikimedia Commons / NASA / USGS / NOAA, public domain or CC. Credit: Wikimedia Commons / NASA / USGS / NOAA, public domain or CC.

Mechanism photograph: Field photograph or official scientific figure for teaching tsunami. Field photograph or official scientific figure for teaching tsunami. A second photograph for the projector script — not the lab cover. Source: Wikimedia Commons / NASA / USGS / NOAA, public domain or CC. Credit: Wikimedia Commons / NASA / USGS / NOAA, public domain or CC.

Two photographs, two jobs. The field picture is the place. The mechanism picture is the process. Do not run the lesson on a single Apollo Earth disc. A carbon-cycle class is a forest and a seam, not a blue marble. An ENSO class is a Pacific temperature map, not Africa from Apollo 17.

Words they must be able to say

Say these out loud once while you click the matching mesh. If a word has no mesh, it still has a photograph in Terms.

Tsunami: Long-period wave from a sudden water displacement, often seafloor slip. Shoaling: Wave slowing and growing as it enters shallow water. Storm surge: Sea-level rise from wind pile-up and low pressure. Not a tsunami. Megathrust: The big subduction fault. Cascadia’s tsunami source. Wavelength: Crest to crest. A tsunami’s is huge in deep water. Drawdown: Sea pulling back before some tsunami crests. Not a reliable gift of time. Run-up: How high the water reaches on land. Not the same as deep-water amplitude.

Exam-language toggle (the Teacher tab) swaps UK/US pairs where they exist — levée/levee, arête/arete — so a mixed room is not punished for spelling.

Close the slot

Without the canvas the machine is still displacement, not wind. Seafloor slip lifts a water column. In deep water a tsunami is fast and low, often unnoticed at sea. At the coast it shoals: slower, taller, energy in a shallower column. It is not a wind storm surge. Surge is wind and pressure. Tide is the Moon and Sun. Tsunami is a sudden shift of water, often a megathrust. Cascadia is the drill. Katrina and Sandy are surge. Do not call the 1953 North Sea flood a tsunami. Green’s law is the story, not a formula dump.

Finish in Check — ten questions, not a mood. The bank mixes definition, process, the misconception you just killed, a named place, and a read-the-model item (click the part; T). If a pupil can only recite the hook, they have not used the geometry. Wrong answers still show the one-line explain. Do not skip the explain.

Sources on the Teacher tab are the trail, not a bibliography to copy. NOAA tsunami; USGS.

Link back to the live lab and keep the same slug. Do not invent a parallel worksheet that contradicts T, SI, or the named parts.

This note is worldwide. Curriculum tags (GCSE; NGSS MS-ESS3-2) are filters, not a flag. A class in Nairobi, London, or Shanghai can use the same 3D. Ages (GCSE, NGSS MS, HS Earth Sci) are a suggested band. If a sentence only works in one exam board, rewrite it before you project it.

Write these three lines on the board before you dim the lights. One: Seafloor slip lifts a water column. In deep water the wave is fast and low. At the coast it stands up. Two: the misconception “A tsunami is a wind storm surge.”. Three: the named parts they must click. Then drive the model. Check is ten questions covering definition, process, the misconception, a place, and a read-the-model item. Do not skip the explain on a wrong answer.

Board, units, and what not to say

SI first. Metres, kilometres, degrees Celsius, metres per second. A conversion in brackets is courtesy, not a second system. Do not let a pupil leave thinking the 3D is a photograph. It is a teaching model. Where vertical exaggeration exists, T collapses it and the caption says so.

Do not say “teaching mesh”, “sprinkle”, or “thin free surface not a fat pipe” out loud. Say the landform. Seasons are ~23.44° of axial tilt, not Earth–Sun distance. The outer core is liquid; S-waves do not pass. Yosemite is a glacial U-trough. San Andreas is a transform. Hawaiʻi and Yellowstone are hotspots. Florida is not a glacial trough.

If the room is noisy, projector layout (P) is the back-row setting: one idea, large type, the model still live. Full screen (F). Labels (L). Space plays. Arrows nudge time. R resets. The URL can remember t, labels, true scale. Send them home with the same link; there is no login.

In-site film

How tsunamis work — Alex Gendler. TED-Ed. TED-Ed on YouTube. Standard YouTube licence. Educational embed, autoplay off. Autoplay off.