Tsunami
A tsunami is a series of waves generated by undersea earthquakes, landslides, volcanic eruptions or meteorites. In Australia, the main threat is from distant sources around the Pacific and Indian Oceans, giving hours of warning, but local sources could give minutes. Know the natural warning signs: a strong or long earthquake felt near the coast, a sudden rise or fall in sea level, or a loud roar from the ocean - these mean evacuate immediately to high ground or inland, without waiting for an official warning.
Understand that the first wave is often not the largest, waves arrive over hours, and the third to eighth waves can be the biggest. Tsunami waves behave like a rapidly rising tide with powerful currents, not a single breaking wave. Vertical evacuation means moving to an upper floor of a sturdy reinforced building if you cannot reach high ground in time. Stay away from beaches, estuaries and rivers until the all-clear.
Traps: questions often test whether to go to the beach to watch - never. Another trap: people return after the first wave, which is deadly. Do not assume a tsunami looks like a surfing wave; it is a surge of water.
Rule of thumb: Feel a strong quake or see the sea recede? Go to high ground immediately; stay there until official all-clear.
Worked example: A long, strong earthquake shakes a coastal town. The correct action is to move inland and uphill immediately, not to wait for a tsunami warning, because the earthquake itself is the warning.