The Pacific Ocean is the world's largest, covering more than one third of the total surface area of our planet. In less than a day, these tsunamis can travel from one side of the Pacific to the other. However, people living near areas where large earthquakes occur may find that the tsunami waves will reach their shores within minutes of the earthquake. The continents and sea floor that cover the earth's surface are part of a world-wide system of plates that are in motion. These motions are very slow, only an inch or two per year.
Earthquakes occur where the edges of plates run into one another.
Such edges are called fault lines or faults. Sometimes the forces along faults can build-up over long periods of time so that when the rocks finally break an earthquake occurs. When powerful, rapid faulting occurs underneath or near the ocean, a large earthquake is produced and, possibly, a tsunami. The deep ocean trenches off the coasts of Alaska, the Kuril Islands, Russia,, and South America are well known for their violent underwater earthquakes and as the source area for destructive Pacific-wide tsunamis. The tsunami generating process is more complicated than a sudden push against the column of ocean water.