Tuesday, April 07, 2009
History Channel:How the Earth Was Made: Tsunamis; the threat of Cumbre Vieja to US East Coast!
On April 7, The History Channel broadcast a major episode of its “How the Earth Was Made,” specifically, “Tsunami”, and, yes, this is equivalent to another “mega-disasters” episode. The link is here.
The early part of the program showed the research linking a tsunami in Japan and Hawaii in 1960 to a devastating earthquake off the coast of Chile. Later, the work of geologist Atwater along the Pacific Northwest coast, examining “notches” and layers of sand, show past tsunamis associated with regular earthquakes along the Cascadia fault. Atwater does research to show that a tsunami occurred along the Washington Coast in January 1700 at the same time one hit Japan.
The program reviewed the 2004 Indian Ocean tsunami which killed over 250000 people and showed that some areas of Indonesia have regular complex cycles of tsunamis.
The speed of tsunamis over deep ocean water is explained. As the tsunami approaches land, the shallow water slows the leading edge down, causing the wave to grown from behind and topple, making the wave much higher. Tsunamis tend to come in a series of repeated waves extending over some hours,
The most dangerous tsunamis might come from landslides rather than directly from undersea earthquakes. In 1958, there was a tsunami that reached over 1000 feet in an inlet in southern Alaska, at Lituya Bay. Here is a USC reference on the event.
The most frightening possibility would be a mega-tsunami on the East Coast, from Newfoundland down to Brazil, from the collapse of the volcanic ridges of the Isla de la Palma in the Canary Islands, with resulting massive landslide, causing perhaps one sixth of the island to disappear. The best known feature is the Cumbre Vieja (with the Caldera de Taburiente), which has long been recognized as having a potential for eruption and collapse; but British geologist Simon Day has found that the entire ridge is much weaker than thought, with many volcanic plugs around the Island providing evidence that the Island is even weaker than thought. A volcanic eruption (which would be 200 times the size of Mt. St. Helens) would result in a huge landslide that would send a tsunami over 100 feet high, perhaps even several hundred feet high, toward the East Coast of the United States in a matter of hours, without much time for evacuations of major cities.
There was a minor eruption on Palma in 1949, which left a lot of volcanic evidence of weakness for Day to find, and there is evidence of tsunamis from avalanches going across the Atlantic in the distant past.
Is it possible to "prepare" for such a mega-catastrophe? How many refugees from the East Coast would have to be housed by FEMA -- or in people's homes beyond the Appalachians (the Eastern Continental Divide), or at least above the Fall Line. Maybe Roland Emmerich ("2012") will make a "disaster movie" about it. This is too much for the old Parker Brother's game of "Star Reporter" -- or maybe it ends the game.
Picture (above): Palma Island, from Wikipedia Commons, NASA photo, in public domain; go to Wikipedia article on “Cumbre Vieja” for attributions. This little island could be the single biggest threat to our way of life!
Update: May 4, 2009
AOL reports that a major tsunami hit the New York harbor about 2000 years ago, possibly the result of an underwater landslide! The link (to story "New York's Tsunami") is this. This is very recent and geological times and certainly an alarming report.