Dear Tom,
What is the difference between a tsunami and a tidal wave?
Dolores Turner, Des Plaines, Ill.
Dear Dolores,
The catastrophic surge that swept the shores of the Indian Ocean on Dec. 26 has put both terms into the news, but the only technically correct word is “tsunami.”
A tsunami is a series of waves generated when an earthquake, landslide, volcanic eruption (all three at or below water) or a meteor impact suddenly displace massive amounts of ocean water. From their source region, the waves spread outward through the ocean, unnoticed because they are only a few feet high, until they mount into gigantic surges at the shore.
Tsunamis are not in any way related to ocean tides and it is incorrect to refer to them as tidal waves, which, in popular usage, are any unusually high, destructive water levels at an ocean shore.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
