If an earthquake lifts or drops part of the ocean floor, the water above it starts moving too. This triggers a tsunami. Oddly, in deep water its waves are only a few feet high. But when the waves approach shore, they increase in energy and height. Often before a tsunami hits, there is a giant vacuum effect, and water is sucked from harbors and beaches.
People see the bare sea bottom littered with flopping fish and stranded boats.
That is because waves are made up of crests, or high points, and troughs, or dips between crests. When a trough hits land first, the water level drops drastically. T sunamis have killed more than 50,000 people in the past century. W e can't tame the tsunami. But we can learn when it's coming and escape the sea monster's fury.