Tuesday, May 13, 2008

Mega Tsunami (History Channel): A cataclysm 8000 years ago; what about Cumbre Vieja today?


The History Channel’s Mega Tsunami, aired May 13, 2008, explores the possibility and likelihood that an eruption of Mount Aetna in Sicily about 8000 years ago started a tsunami that spread through the Mediterranean as far as modern day Israel. At the time, civilization was beginning to build cities and develop agriculture and settle down; social institutions were following suit.

An “Adventuring Hike” on Mount Etna shows a huge cliff facing the sea, from which several cubic miles may have slid into the Mediterranean after a pyroclastic eruption. A similar slide occurred on land on Mt. St. Helens in Washington in 1980. The best evidence that human settlement was destroyed is found under the sea near Haifa, with a buried settlement called Attlit Yam. Fossils of abandoned commodities are found; early civilization could not be a consumerist society like ours with fiat money, and people stored goods.

The show discussed the physics of tsunamis. The Etna tsunami would have been 165 feet high in some areas. The Indonesia tsunami on Dec. 26, 2004 was 90 feet high at its greatest and was “smaller”.

Tsunamis care caused by earthquakes and by landslides from earthquakes or volcanoes. Those caused by landslides carry along a lot of seabed sediment.

There is some threat that cataclysmic tsunamis could happen again. For example a slide off of Mauna Loa on Hawaii could reach Oahu and Honolulu. More serious is the threat posed by the Cumbre Vieja in the Canary Islands off north Africa. That could generate a 300 foot tsunami at Morocco and a 150 wall of water reach the East Coast of the US and Canada from Newfoundland to Florida in about 8 hours, wiping out a hundred million people. Could they be evacuated? Would the Fall Line and Piedmont be high enough? (I remember a question about the Fall Line on my 11th Grade history final!)

The Cumbre Vieja erupted in 1949, leaving a crack in the mountain that could give way some day. Wiki reference.

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