Ancient Crash, Epic Wave

[phongn]

November 14, 2006
Ancient Crash, Epic Wave
By SANDRA BLAKESLEE

Correction Appended

At the southern end of Madagascar lie four enormous wedge-shaped sediment deposits, called chevrons, that are composed of material from the ocean floor. Each covers twice the area of Manhattan with sediment as deep as the Chrysler Building is high.

On close inspection, the chevron deposits contain deep ocean microfossils that are fused with a medley of metals typically formed by cosmic impacts. And all of them point in the same direction — toward the middle of the Indian Ocean where a newly discovered crater, 18 miles in diameter, lies 12,500 feet below the surface.

The explanation is obvious to some scientists. A large asteroid or comet, the kind that could kill a quarter of the world’s population, smashed into the Indian Ocean 4,800 years ago, producing a tsunami at least 600 feet high, about 13 times as big as the one that inundated Indonesia nearly two years ago. The wave carried the huge deposits of sediment to land.

Most astronomers doubt that any large comets or asteroids have crashed into the Earth in the last 10,000 years. But the self-described “band of misfits” that make up the two-year-old Holocene Impact Working Group say that astronomers simply have not known how or where to look for evidence of such impacts along the world’s shorelines and in the deep ocean.

Scientists in the working group say the evidence for such impacts during the last 10,000 years, known as the Holocene epoch, is strong enough to overturn current estimates of how often the Earth suffers a violent impact on the order of a 10-megaton explosion. Instead of once in 500,000 to one million years, as astronomers now calculate, catastrophic impacts could happen every 1,000 years.

The researchers, who formed the working group after finding one another through an international conference, are based in the United States, Australia, Russia, France and Ireland. They are established experts in geology, geophysics, geomorphology, tsunamis, tree rings, soil science and archaeology, including the structural analysis of myth. Their efforts are just getting under way, but they will present some of their work at the American Geophysical Union meeting in December in San Francisco.

This year the group started using Google Earth, a free source of satellite images, to search around the globe for chevrons, which they interpret as evidence of past giant tsunamis. Scores of such sites have turned up in Australia, Africa, Europe and the United States, including the Hudson River Valley and Long Island.

When the chevrons all point in the same direction to open water, Dallas Abbott, an adjunct research scientist at Lamont-Doherty Earth Observatory in Palisades, N.Y., uses a different satellite technology to look for oceanic craters. With increasing frequency, she finds them, including an especially large one dating back 4,800 years.

So far, astronomers are skeptical but are willing to look at the evidence, said David Morrison, a leading authority on asteroids and comets at the NASA Ames Research Center in Mountain View, Calif. Surveys show that as many as 185 large asteroids or comets hit the Earth in the far distant past, although most of the craters are on land. No one has spent much time looking for craters in the deep ocean, Dr. Morrison said, assuming young ones don’t exist and that old ones would be filled with sediment.

Astronomers monitor every small space object with an orbit close to the Earth. “We know what’s out there, when they return, how close they come,” Dr. Morrison said. Given their observations, “there is no reason to think we have had major hits in the last 10,000 years,” he continued, adding, “But if Dallas is right and they find 10 such events, we’ll have a real contradiction on our hands.”

Peter Bobrowski, a senior research scientist in natural hazards at the Geological Survey of Canada, said “chevrons are fantastic features” but do not prove that megatsunamis are real. There are other interpretations for how chevrons are formed, including erosion and glaciation. Dr. Bobrowski said. It is up to the working group to prove its claims, he said.

William Ryan, a marine geologist at the Lamont Observatory, compared Dr. Abbott’s work to that of other pioneering scientists who had to change the way their colleagues thought about a subject.

“Many of us think Dallas is really onto something,” Dr. Ryan said. “She is building a story just like Walter Alvarez did.” Dr. Alvarez, a professor of earth and planetary sciences at the University of California, Berkeley, spent a decade convincing skeptics that a giant asteroid wiped out the dinosaurs 65 million years ago.

Ted Bryant, a geomorphologist at the University of Wollongong in New South Wales, Australia, was the first person to recognize the palm prints of mega-tsunamis. Large tsunamis of 30 feet or more are caused by volcanoes, earthquakes and submarine landslides, he said, and their deposits have different features.

Deposits from mega-tsunamis contain unusual rocks with marine oyster shells, which cannot be explained by wind erosion, storm waves, volcanoes or other natural processes, Dr. Bryant said.

“We’re not talking about any tsunami you’re ever seen,” Dr. Bryant said. “Aceh was a dimple. No tsunami in the modern world could have made these features. End-of-the-world movies do not capture the size of these waves. Submarine landslides can cause major tsunamis, but they are localized. These are deposited along whole coastlines.”

For example, Dr. Bryant identified two chevrons found over four miles inland near Carpentaria in north central Australia. Both point north. When Dr. Abbott visited a year ago, he asked her to find the craters.

To locate craters, Dr. Abbott uses sea surface altimetry data. Satellites scan the ocean surface and log the exact height of it. Underwater mountain ranges, trenches and holes in the ground disturb the Earth’s gravitational field, causing sea surface heights to vary by fractions of an inch. Within 24 hours of searching the shallow water north of the two chevrons, Dr. Abbott found two craters.

Not all depressions in the ocean are impact craters, Dr. Abbott said. They can be sink holes, faults or remnant volcanoes. A check is needed. So she obtained samples from deep sea sediment cores taken in the area by the Australian Geological Survey.

The cores contain melted rocks and magnetic spheres with fractures and textures characteristic of a cosmic impact. “The rock was pulverized, like it was hit with a hammer,” Dr. Abbott said. “We found diatoms fused to tektites,” a glassy substance formed by meteors. The molten glass and shattered rocks could not be produced by anything other than an impact, she said.

“We think these two craters are 1,200 years old,” Dr. Abbott said. The chevrons are well preserved and date to about the same time.

Dr. Abbott and her colleagues have located chevrons in the Caribbean, Scotland, Vietnam and North Korea, and several in the North Sea.

Hither Hills State Park on Long Island has a chevron whose front edge points to a crater in Long Island Sound, Dr. Abbott said. There is another, very faint chevron in Connecticut, and it points in a different direction.

Marie-Agnès Courty, a soil scientist at the European Center for Prehistoric Research in Tautavel, France, is studying the worldwide distribution of cosmogenic particles from what she suspects was a major impact 4,800 years ago.

But Madagascar provides the smoking gun for geologically recent impacts. In August, Dr. Abbott, Dr. Bryant and Slava Gusiakov, from the Novosibirsk Tsunami Laboratory in Russia, visited the four huge chevrons to scoop up samples.

Last month, Dee Breger, director of microscopy at Drexel University in Philadelphia, looked at the samples under a scanning electron microscope and found benthic foraminifera, tiny fossils from the ocean floor, sprinkled throughout. Her close-ups revealed splashes of iron, nickel and chrome fused to the fossils.

When a chondritic meteor, the most common kind, vaporizes upon impact in the ocean, those three metals are formed in the same relative proportions as seen in the microfossils, Dr. Abbott said.

Ms. Breger said the microfossils appear to have melded with the condensing metals as both were lofted up out of the sea and carried long distances.

About 900 miles southeast from the Madagascar chevrons, in deep ocean, is Burckle crater, which Dr. Abbott discovered last year. Although its sediments have not been directly sampled, cores from the area contain high levels of nickel and magnetic components associated with impact ejecta.

Burckle crater has not been dated, but Dr. Abbott estimates that it is 4,500 to 5,000 years old.

It would be a great help to the cause if the National Science Foundation sent a ship equipped with modern acoustic equipment to take a closer look at Burckle, Dr. Ryan said. “If it had clear impact features, the nonbelievers would believe,” he said.

But they might have more trouble believing one of the scientists, Bruce Masse, an environmental archaeologist at the Los Alamos National Laboratory in New Mexico. He thinks he can say precisely when the comet fell: on the morning of May 10, 2807 B.C.

Dr. Masse analyzed 175 flood myths from around the world, and tried to relate them to known and accurately dated natural events like solar eclipses and volcanic eruptions. Among other evidence, he said, 14 flood myths specifically mention a full solar eclipse, which could have been the one that occurred in May 2807 B.C.

Half the myths talk of a torrential downpour, Dr. Masse said. A third talk of a tsunami. Worldwide they describe hurricane force winds and darkness during the storm. All of these could come from a mega-tsunami.

Of course, extraordinary claims require extraordinary proof, Dr. Masse said, “and we’re not there yet.”

Correction: Nov. 16, 2006

An article in Science Times on Tuesday about new research suggesting that a comet or an asteroid may have struck the Indian Ocean 4,800 years ago included an incorrect estimate from researchers for the frequency of such collisions. The current estimate is one impact on the order of a 10-megaton bomb every 1,000 years, not every few thousand years. The article also misstated the name of a state park on Long Island that has a large sand wedge called a chevron, which may indicate that a comet or meteor landed in the ocean nearby. It is Hither Hills, not Heather Hill.

[Ariphaos]

Huh. It fits, better than the thoroughly-debunked Black Sea flooding myth.

Will have to see what more research describes.

[Surlethe]

See, this is how you go about overturning established scientific conclusions: you find evidence, document it, peer-review it, and then present it or get it published. This is yet more evidence against the grand creationist scientific conspiracy of the status quo.

Surveys show that as many as 185 large asteroids or comets hit the Earth in the far distant past, although most of the craters are on land. No one has spent much time looking for craters in the deep ocean, Dr. Morrison said, assuming young ones don’t exist and that old ones would be filled with sediment.

Wouldn't 150 large impacts on land, if asteroids hit randomly, imply some three and a third times that total, since the Earth is seventy percent covered in water right now?

[Darth Wong]

Asteroid impacts are inevitable, so it's not too unreasonable to speculate on an asteroid impact causing a tsunami. Mind you, it's not that revolutionary, and the bit about tying it to a particular date within the last 10,000 years because of flood myths is just crackpottery at this point. The article conspicuously didn't even mention how they were arriving at their date estimates, except for the one guy who was "analyzing myths".

[Ariphaos]

Wouldn't 150 large impacts on land, if asteroids hit randomly, imply some three and a third times that total, since the Earth is seventy percent covered in water right now?

The ocean floor is generally the youngest bit of the Earth - being the densest material, not only is it subject to the most erosion, but also subducts more often, erasing oceanic craters. So most of the remaining ones are on land.

[Rye]

A 600ft tall wall of water is something I want to see. The sheer doom you'd feel looking at that thing...goddamn.

[Darth Wong]

A 600ft tall wall of water is something I want to see.

Large asteroid impacts would cause waves as high as 4 km.

[Rye]

Yeah, but a 4km high wave is much more likely to kill me, so I'm not as keen.

[CmdrWilkens]

Asteroid impacts are inevitable, so it's not too unreasonable to speculate on an asteroid impact causing a tsunami. Mind you, it's not that revolutionary, and the bit about tying it to a particular date within the last 10,000 years because of flood myths is just crackpottery at this point. The article conspicuously didn't even mention how they were arriving at their date estimates, except for the one guy who was "analyzing myths".

They didn't mention for the largest crater but fro at least the Australian one they mentioned pulling core samples which suggests that they tried to date that one precisely. The article also seemed to suggest that the flood myth analysis was secondary to the overall work especially as it wasn't mentioned until long after discussing how they go crater hunting.

[Setesh]

Yeah, but a 4km high wave is much more likely to kill me, so I'm not as keen.

if your close enough to enjoy the view, your pretty likely to die from a 600ft wave as well. Not counting the acceleration of the wave that would be (rounded) 876psi of very sudden pressure.

[Bedlam]

Yeah, but a 4km high wave is much more likely to kill me, so I'm not as keen.

I think a 600m waves quite likely to kill you if you can see it

[Pelranius]

That's what satelite photos are for.

I wonder if this impact would have had a hand in causing the Sahara to dry up?

[Surlethe]

Wouldn't 150 large impacts on land, if asteroids hit randomly, imply some three and a third times that total, since the Earth is seventy percent covered in water right now?

The ocean floor is generally the youngest bit of the Earth - being the densest material, not only is it subject to the most erosion, but also subducts more often, erasing oceanic craters. So most of the remaining ones are on land.

Yes, most of the remaining craters are on land, but since about 1/3 of the Earth's surface is land, can we reasonably assert that about 2/3 of the impact craters have been in the ocean and subsequently erased?

[Frank Hipper]

But they might have more trouble believing one of the scientists, Bruce Masse, an environmental archaeologist at the Los Alamos National Laboratory in New Mexico. He thinks he can say precisely when the comet fell: on the morning of May 10, 2807 B.C.

Dr. Masse analyzed 175 flood myths from around the world, and tried to relate them to known and accurately dated natural events like solar eclipses and volcanic eruptions. Among other evidence, he said, 14 flood myths specifically mention a full solar eclipse, which could have been the one that occurred in May 2807 B.C.

Hear that sound? It's the sound of credibility flying out the window.

[Magus]

Yes, most of the remaining craters are on land, but since about 1/3 of the Earth's surface is land, can we reasonably assert that about 2/3 of the impact craters have been in the ocean and subsequently erased?

Why do you say that? Unless I'm reading it wrong, didn't it say that both of the impact craters found to date were in some form of water? One 12,500 feet below the surface, the other in shallower water. Neither of those were erased.

[Sriad]

Yes, most of the remaining craters are on land, but since about 1/3 of the Earth's surface is land, can we reasonably assert that about 2/3 of the impact craters have been in the ocean and subsequently erased?

Why do you say that? Unless I'm reading it wrong, didn't it say that both of the impact craters found to date were in some form of water? One 12,500 feet below the surface, the other in shallower water. Neither of those were erased.

Erasure happens very quickly in geological time in the oceans(on the scale of thousands of years by filling with sediment, on the scale of millions of years by being subducted back into the mantel), but not fast enough to erase evidence of these very recent impacts.

[Magus]

Erasure happens very quickly in geological time in the oceans(on the scale of thousands of years by filling with sediment, on the scale of millions of years by being subducted back into the mantel), but not fast enough to erase evidence of these very recent impacts.

Then, wouldn't the percent that has survived be:

1.00 = Land + Sea
Assuming all land survive, and assuming a 1 to 2 ratio of land and sea strikes:

.33 + .66 * (x/y)%, where y = total number of years Earth has been struck, and x = number of years that collisions would not have had time to erode.

= total impact sites still in existence?

This assumes, of course, a consistent meteor fall over the entirety of the system.

[Kitsune]

But they might have more trouble believing one of the scientists, Bruce Masse, an environmental archaeologist at the Los Alamos National Laboratory in New Mexico. He thinks he can say precisely when the comet fell: on the morning of May 10, 2807 B.C.

Dr. Masse analyzed 175 flood myths from around the world, and tried to relate them to known and accurately dated natural events like solar eclipses and volcanic eruptions. Among other evidence, he said, 14 flood myths specifically mention a full solar eclipse, which could have been the one that occurred in May 2807 B.C.

Hear that sound? It's the sound of credibility flying out the window.

When there is somethink like that, there is an agenda

[Kitsune]

Huh. It fits, better than the thoroughly-debunked Black Sea flooding myth.

Debunked that the Black Sea flood did not happen or that it is the origin of the myths.

The evidence for the first seemed pretty compelling but the second I was always skeptical about

[CaptainChewbacca]

Kitsune- The Black Sea flooding would have been too early in history for it to effectively enter the human consciousness. As for this new method of crater-searching, I find no flaws in their methodology. Large beach chevrons have always been good indicators of tsunamis. I look forward to more findings from them, and if anyone has any geology/meteor impact questions, feel free.

[Sriad]

Then, wouldn't the percent that has survived be:

1.00 = Land + Sea
Assuming all land survive, and assuming a 1 to 2 ratio of land and sea strikes:

.33 + .66 * (x/y)%, where y = total number of years Earth has been struck, and x = number of years that collisions would not have had time to erode.

= total impact sites still in existence?

This assumes, of course, a consistent meteor fall over the entirety of the system.

No no. Here are some made up numbers to illustrate what we're getting at.

T=Average time required for 75% of all craters of size X to be 100% hidden, obscured, destroyed, or otherwise placed beyond the reach of human detection.
T(crater X on land)=1,000,000 years
T(crater X in ocean)=50,000 years
So even though there are twice as many impacts in the ocean as on land, they only LAST 1/20th as long so there appear to be far fewer.

[Ariphaos]

Debunked that the Black Sea flood did not happen or that it is the origin of the myths.

The evidence for the first seemed pretty compelling but the second I was always skeptical about

I thought it was extremely awesome at first, and very plausible, until I stumbled across a geological work that utterly demolished the entire Black Sea flood. Case in point: The Black Sea flows into the Mediterranean, not the reverse. It also went over the adaptation of life in the region.

...wow, here is a case example of where Wikipedia and even Google utterly fails, hard. I really need to dig out that journal. I think it's about five or six years old, now, I found it on-line but not through Google :-/

Incidentally. the Marmara sea -did- flood in that time period, and the Turks have a rather absurd legend that still recalls it appropriately - the Black Sea was originally a large freshwater sea, eventually overflowing into the Marmara and then into the Mediterranean. It's not too early into the human consciousness - hell, the Native Americans have some pretty clear legends regarding ancient geological floods too.

[Quadlok]

If this happened so recently, shouldn't the Sumerians or Egyptians or some other early civilization have written about it? There were already several literate cultures near the Indian Ocean 5000 years ago.

[Singular Intellect]

A 600ft tall wall of water is something I want to see. The sheer doom you'd feel looking at that thing...goddamn.

Large asteroid impacts would cause waves as high as 4 km.

I have to admit, the sheer personal awe such scenarios would invoke in me would be a rush.

Makes me wonder if I'd feel any fear, really, since witnessing such an event pretty much ensures I won't be surviving it. I wouldn't bother trying to outrun it or hide from it. I suppose it would be a battle between my animal instincts and intellectual grasp of the situation...

[Junghalli]

Makes me wonder if I'd feel any fear, really, since witnessing such an event pretty much ensures I won't be surviving it. I wouldn't bother trying to outrun it or hide from it. I suppose it would be a battle between my animal instincts and intellectual grasp of the situation...

Well, I don't know about you but I don't think I could really properly - ah - appreciate such an awesome spectacle if I was actually in front of it. It's awesome to think about intellectually but I think if I actually saw a wall of water dwarfing a skyscraper coming at me any appreciation of its grandeur would be drowned under stark, overwhelming terror.