EP1 · Tsunamis
Every definite tsunami source mapped across two millennia, sized by the water it raised and coloured by what caused it: earthquakes mostly, volcanoes and landslides for the rest.
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A tsunami is water displaced in bulk, then set free to spread. Most are born when an undersea earthquake suddenly lifts or drops the seabed; the rest come from volcanoes and from landslides, including rock and ice falling into fjords.
In the open ocean a tsunami is often only centimetres tall and passes ships unnoticed, travelling at the speed of an airliner. It becomes a disaster only where the seabed shoals and those centimetres pile into metres against the coast.
The number that matters is runup: the height the water reaches on land above the tide. It is what floods streets and takes lives, and it can differ wildly along a single coast depending on the shape of the seabed and the bays.
The NOAA historical database reaches back to antiquity, but the further back you go the thinner the evidence. Many old entries rest on a single chronicle and could be storms, floods or legend.
So the map defaults to events the record marks definite, and lets you widen the lens at the cost of certainty. The instrumental era, roughly since 1900, is where the catalogue is most complete.
The full catalogue: year, source, cause, earthquake magnitude, maximum water height, runup count and toll for every recorded tsunami.
The deadliest tsunami in history. A magnitude 9.1 Sumatran megathrust sent waves up to 50.9 metres ashore and killed around 227,899 people in 14 countries with no warning system between them.