According to University of Washington geologist and tsunami expert Jody Bourgeois, the idea that chevrons – a type of large U- or V-shaped formations found along certain coasts – were caused by mega-tsunamis is pure nonsense.

The term chevron refers a special type of vast dunes shaped a bit like the stripes on soldier’s uniform. They can be anything from hundreds of meters to a kilometre in length and can be seen in places such as Egypt, the Bahamas, Madagascar, and Australia.

Some scientists have suggested that a possible explanation for these mysterious stripes is mega-tsunamis caused by asteroid or comet impact. According to this school of thought, the chevrons may be deposits left by gigantic tsunamis 4,800 to 5,000 years ago, tsunamis that might have been up to 10 times larger than the earthquake-caused Indian Ocean tsunami of December 2005. Due to the location of known chevrons, the Indian Ocean has been suggested as ground zero for the comet or asteroid impact.

Bourgeois, a professor of Earth and space sciences who has studied earthquakes and tsunamis in various parts of the world, does not agree. According her, the chevrons are not lined up the way you would expect from deposits caused by gigantic waves. Many of the chevrons on Madagascar are for instance parallel to the coastline, instead of perpendicular to the shore.

Models created by Bourgeois’ colleague Robert Weiss, assistant professor of geology at

Texas A&M University, show that deposits formed by gigantic tsunamis would point in the same direction as the waves were travelling when the reached land, which is 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,” Bourgeois explains.

The computer model generated actual conditions for a tsunami which made it possible to use the model to explore the effects of an asteroid or comet hitting the part of the Indian Ocean suggested by mega-tsunami chevron proponents. According to the model, the gigantic waves would approach land at a 90-degree orientation to the chevron deposits.

“The model shows such a tsunami could not have created these chevrons, unless you have some unimaginable process at work,” Bourgeois says.

Bourgeois and Weiss have used satellite images from Google Earth to get close-up looks at chevrons in different locations. Chevron are most common in coastal regions but you can find quite a lot of them in semiarid inland areas as well.

Bourgeois and Weiss wrap up their paper, which can be found in the May issue of the journal Geology, by stating that “the extraordinary claim of ‘chevron’ genesis by megatsunamis cannot withstand simple but rigorous testing. […] There are the same forms in the Palouse in eastern Washington state, and those are clearly not from a tsunami.”