EARTH SCIENCE SERVICES > ENVIRONMENTAL ADVISORIES > MARINE ADVISORIES > TSUNAMIS
A long-period (usually 15-60 minutes) wave caused by a large-scale movement of
the sea floor, from a volcanic eruption, submarine earthquake, or landslide
although usually barely noticeable at sea, its velocity may be as high as 400
knots, so that it travels great distances and in shoal water may reach heights
of around 15 meters.
AP Dictionary of Science and Technology: