Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Contrary to Recent Hypothesis, 'Chevrons' Are Not Evidence of Megatsunamis

30.04.2009
Two geologists are debunking the recent notion 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.

A persistent school of thought in recent years has held that so-called "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.

University of Washington geologist and tsunami expert Jody Bourgeois has a simple response: Nonsense.

The term "chevron" was introduced to describe large dunes shaped something like the stripes you 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.

In a paper in the May issue of Geology, Bourgeois and Weiss, an assistant professor of geology at Texas A&M University, conclude that "the extraordinary claim of 'chevron' genesis by megatsunamis cannot withstand simple but rigorous testing."

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.

"There are the same forms in the Palouse in eastern Washington state, and those are clearly not from a tsunami," Bourgeois said.

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.

Asteroids and comets bombarded Earth in the distant past, at times with devastating consequences, such as the impact 65 million years ago that is believed to have sent dinosaurs to their extinction. There have been large impacts since but probably nothing comparable.

Proponents of the megatsunami theory have suggested that the dunes could not have been created by other forces, but Bourgeois believes their interpretation is faulty.

"They claim these are not consistent with the patterns of prevailing winds, but in fact they are consistent with the wind. They are not consistent with what a tsunami would do," she said.

The discovery of marine fossils in some chevron formations seems to support the idea that a wave created the deposit, but Bourgeois discounts that evidence also.

"Marine fossils can get into non-marine deposits. It's not uncommon. You only have to change sea level a little bit or have them wash up on a beach in a storm," she said. "And some marine organisms can be carried by the wind. I am convinced these are largely wind-blown deposits."

She noted that similar deposits have been seen on the Kamchatka Peninsula on Russia's east coast, where she has conducted research for more than a decade.

"Those are made of volcanic ash, and they are not near the coast at all, yet they look very similar to these coastal chevrons," Bourgeois said.

For more information, contact Bourgeois at (206) 685-2443 or bourgeois@ess.washington.edu.

Vince Stricherz | Newswise Science News
Further information:
http://www.washington.edu

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Tracking movement of immune cells identifies key first steps in inflammatory arthritis

23.01.2017 | Health and Medicine

Electrocatalysis can advance green transition

23.01.2017 | Physics and Astronomy

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>