WASHINGTON - A new research has refuted the hypothesis that ‘chevrons’, large U- or V-shaped formations found in some of the world’s coastal areas, are evidence of megatsunamis caused by asteroids or comets slamming into the ocean.
The research was done by University of Washington (UW) geologist and tsunami expert Jody Bourgeois.
The term “chevron” was introduced to describe large dunes shaped something like the stripes one might see on a soldier’s uniform that are hundreds of meters to a kilometer in size and were originally found in Egypt and the Bahamas.
But, the discovery of similar forms in Australia and Madagascar led some scientists to theorize that they were, in fact, deposits left by huge tsunami waves, perhaps 10 times larger than the devastating Indian Ocean tsunami of December 2005.
Such huge waves, they suggest, would result from the giant splash of an asteroid or comet hitting the ocean.
They also suggest one such impact occurred 4,800 to 5,000 years ago, and that chevrons in Australia and Madagascar point to its location in the Indian Ocean.
But, Bourgeois said the theory just doesn’t hold water.
For example, she said, there are numerous chevrons on Madagascar, but many are parallel to the coastline.
Models created by Bourgeois’ colleague Robert Weiss show that if they were created by tsunamis, they should point in the direction the waves were travelling, mostly perpendicular to the shore.
“And if it really was from an impact, you should find evidence on the coast of Africa too, since it is so near,” said Bourgeois, a UW professor of Earth and space sciences who has studied earthquakes and tsunamis in various parts of the world.
The scientists used an online program called Google Earth, made up of satellite images of the Earth’s surface, to get close-up looks at chevrons in different locations.
Chevrons often are found in coastal areas, but they also are common in semiarid areas inland.
For the research, Weiss created a computer model that generated actual conditions that would occur during a tsunami.
The scientists then used the model to examine what would happen if an asteroid or comet hit in the area theorized by the megatsunami proponents.
The model showed the wave approach would be at a 90-degree orientation to the chevron deposits. But, if the megatsunami interpretation is correct, the chevrons should be parallel to wave approach.
“That’s just not the case here. The model shows such a tsunami could not have created these chevrons, unless you have some unimaginable process at work,” Bourgeois said. (ANI)
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