[meteorite-list] Big Splash Theory Says Meteors Hit Regularly

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Nov 14 12:25:47 2006
Message-ID: <200611141725.JAA07427_at_zagami.jpl.nasa.gov>

http://www.nytimes.com/2006/11/14/science/14WAVE.html

Ancient Crash, Epic Wave
By SANDRA BLAKESLEE
New York Times
November 14, 2006

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 few thousand 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.

Heather Hill 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-Agn?s 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."

-----------------------------------------------------------------------

http://www.smh.com.au/news/world/big-splash-theory-says-meteors-hit-regularly/2006/11/14/1163266554476.html

Big splash theory says meteors hit regularly
Sandra Blakeslee
New York Times
November 15, 2006

A LARGE asteroid or comet, the kind that could kill a quarter of the
world's population, smashed into the Indian Ocean 4800 years ago,
producing a tsunami more than 180 metres high - about 13 times as big as
the one that hit Indonesia almost two years ago.

The startling claim is made by a group of researchers, including
Australians, who cite as evidence a newly discovered crater, 29
kilometres in diameter, 3800 metres below the surface of 1600 kilometres
south-east of Madagascar.

Most astronomers doubt that any large comets or asteroids have crashed
into the Earth in the past 10,000 years. But the self-described "band of
misfits" that make up the Holocene Impact Working Group say 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 past 10,000 years is strong enough to overturn 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 1 million years, as astronomers
now calculate, catastrophic impacts could happen every few thousand years.

The researchers, who formed the working group after finding one another
through an international conference, are based in the US, Australia,
Russia, France and Ireland. This year the group started using Google
Earth, a free source of satellite images, to search the globe for
chevrons - enormous wedge-shaped sediment deposits, that are composed of
material from the ocean floor - which they interpret as evidence of past
giant tsunamis.

Ted Bryant, a geomorphologist at the University of Wollongong, was the
first person to recognise the palm prints of mega-tsunamis. Large
tsunamis of 10 metres or more were caused by volcanoes, earthquakes and
submarine landslides, Dr Bryant said, and their deposits have different
features.

Deposits from mega-tsunamis contained unusual rocks with marine oyster
shells, which could not be explained by wind erosion, storm waves,
volcanoes or other natural processes, he said.

"We're not talking about any tsunami you've ever seen. Aceh was a
dimple. No tsunami in the modern world could have made these features."
Dr Bryant identified two chevrons found about six kilometres inland from
the Gulf of Carpentaria. Both point north.

When Dallas Abbott, an adjunct research scientist at Lamont-Doherty
Earth Observatory, in New York, 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
a centimetre. Within 24 hours of searching the shallow water north of
the two chevrons she found two craters.

She obtained samples from deep sea sediment cores taken in the area by
the Australian Geological Survey.

"We think these two craters are 1200 years old," she said. The chevrons
are well preserved and date to about the same time.
Received on Tue 14 Nov 2006 12:25:40 PM PST