Saturday, 3 January 2009

A 13000 year old Whodunnit

Who Killed the Clovis People? One possibility: It was the Universe, with Meteorites, in North America.

From the New York Times :
The meteors would have been smaller than the six-mile-wide meteor that struck the Yucat√°n peninsula 65 million years ago and led to the mass extinctions of the dinosaurs. The killing effects of the hypothesized bombardment 12,900 years ago would have been more subtle.

Climatologists believe that the direct cause of the 1,300-year cold spell, known as the Younger Dryas, was a sudden rush of fresh water from a giant lake in central Canada to the North Atlantic.

Usually a surface current of warm water flows northward in the Atlantic toward Greenland and Europe, then cools and sinks, returning south in the deep ocean. But the fresh water, which is less dense, blocked the sinking of the cold, salty water in the North Atlantic, disrupting the currents.

That sudden change in plumbing has long been known, but what caused it has never been satisfactorily explained.

The authors of the paper in Science say it was meteors.
Like much of Science, it's a detective puzzle. We have clues, parts of the jigsaw, and it's up to us to look for more parts while fitting together what we have into a coherent whole. Some of the parts fit really well:
At each site the scientists looked at, the diamond layer in the rocks correlates to the date of the hypothesized impact. Within the layer, the scientists report finding a multitude of diamond particles, all encased within carbon spheres. “We’ve yet to find a single diamond above it,” Dr. West said. “We’ve yet to find a single diamond below it.”

Perhaps more telling, the scientists reported last month at a meeting of the American Geophysical Union in San Francisco, the carbon atoms inside some of the diamonds are lined up in a hexagonal crystal pattern instead of the usual cubic structure. The hexagonal diamonds, formed by extraordinary heat and pressure, have been found only at impact craters and within meteorites and cannot be formed in forest fires or volcanic eruptions, Dr. West said.

Last year the scientists presented other evidence of an impact, including elevated levels of the element iridium.
Some though might be from another puzzle altogether.
At least some skeptics are not convinced. “The whole thing still does not make sense, and there are lots of contradictions,” said Christian Koeberl, a professor of geological sciences at the University of Vienna in Austria.

His chief reservation is that there is no crater. “A body of this size does not just blow up without a trace in the atmosphere,” Dr. Koeberl said. “Physics won’t have it.”

Proponents have suggested that the meteor hit an ice sheet a couple of miles thick or that there was a series of smaller objects that exploded in the air. But Dr. Koeberl said something hitting an ice sheet would still generate a hole in the ground underneath, and he questioned whether smaller impacts or air explosions would produce the shock waves needed to make diamonds.

An impact should also have left remnants of melted rocks and shocked minerals, Dr. Koeberl said.
Science is like that. Eventually the contradictions are resolved, though gaps may remain, and a new, better picture emerge in time. Most of what we think we know now is correct, but almost all of it is incomplete. Some is just plain wrong of course, but usually it's merely an approximation that has exceptions we don't know about yet.
But if true, the hypothesis could explain the disappearance of ice age mammals like mammoths and argue against the alternative idea that the animals were hunted to extinction by humans.

It might also help explain the disappearance of the Clovis people, a culture named after a distinctive arrow point discovered in a mammoth skeleton in Clovis, N.M., who are believed to have arrived in the Americas more than 13,000 years ago.

Douglas J. Kennett, a University of Oregon archaeologist who is the lead author of the Science paper, said no Clovis points or bones of the extinct animals had been found above the diamond layer. “It seems those two things synchronously end,” he said.

Dr. Kennett said there also appeared to be a gap of several centuries between the disappearance of the Clovis and the resettlement by other people.

Gary Huss, a scientist at the University of Hawaii, Manoa, who was one of the early reviewers of the paper in Science, said though the scientists had not proved their case, they had offered enough evidence that the idea warranted a closer look by others.

“They have a hypothesis that explains several things that hard to explain any other way,”
Did I mention that Science is Fun?


Battybattybats said...

Hmmm.... but what about the rest of the megafauna extinctions outside the USA?

Calamity Jane said...

Strictly O/T response - helloooooo! Happy New Year. Thank you for being you and visiting to say so. I'm trying really hard to get to grips with everything life keeps throwing at me but it feels like a war of attrition sometimes.

Zoe Brain said...

Hi Jane! Good to hear from you!

Just remember, for each hour under GA, it takes a month to get it out of your system. Double that if it involves kidneys. You had major surgery, plus complications.

Rest up, let the world turn without you.

Thanks so much for popping round to say "hi" - that was really thoughtful.

Love to Captain Scarlet, please tell him to take things easy too.

Hugs, Zoe

Samantha said...

Yes, science is fun, but quite often utterly clueless. Did they what fail basic physics? Water is two things other than wet. One it is an amazing conductor, and two it cannot be compressed.

Hitting an ice sheet, yes the ground beneath would have an impact crater. However. An ice sheet of sufficient thickness will a large enough body of water beneath it, is going to significantly attenuate the impact event. Lakes almost NEVER freeze completely solid. It's a little thing known as thermodynamics. Below a certain depth ground remains at a fairly constant 55 degrees. A sheet of ice above it is freezing cold. Thus a little thing known as convection. Even a small amount of convection, or movement prevents lakes from freezing past a certain depth. Just ask and ice fisherman who spends hours cutting a hole so he can go fishing. Fish survive, and are moving. Thus aiding convection, and preventing the water from freezing below a certain depth.

Still with me?

Impact with a block of ice of a sufficient body of water below it is going to act as a sort of shield for the ground beneath it all. At impact, the kinetic energy of the object is going to instantly be released in an amazing amount of motion turned into raw energy. With the right amounts of mass,energy and water beneath . . . BOOM and no crater. The kinetic energy gets loosed in the shock wave of impact, the turning the ice back into water, and the water conducting the energy sideways. The surface tension acts as a reflector, dispersing the atomized meteor fragments into atmo, which then disperses it over a vast area. It happens at a quantum level. Why? Because matter can neither be created, nor destroyed. I just changes state. some into pure energy, some into atomized dust and so forth. Frankly I'd be surprised if there WAS a crater in the ground.

Science has become, like medicine, over specialized, the right pinky doesn't know what the left pinky is doing. Similarly the folks worried about the Clovis folks, don't necessarily know about Quantum Physics. Heck even Quantum folks don't know about quantum physics because they are still fighting about it. Put them in the same room and everyone WILL BE talking a different language and get nothing done. Trust me, I've been there done that.

But hey, what do I know. Because my brother asked me for help with something he was working on I designed two different generators that run on either garbage, or water, and produce power AND clean pure water at the same time. Best of all? No moving parts. Just a release of energy and electro-thermo-dynamics.

I expect they'll be showing up to pay me to shut the hell up, or they'll try and kill me.

One of my nicknames around these parts is "Carter" after Colonel Samantha Carter, PH.D, USAF from the hit series Stargate SG-1.

Anyway, as my family is fond of saying: "You should be very careful using the word HOW around her. She'll tell you."

Samantha "Carter"

Samantha said...

Oh, yeah, one last thing. Did they think all that fresh water got up and walked into the ocean? Water expands when it freezes. Any water converted from ice by the quantum side of the impact event will wind up in atmo as steam. The Lake can hold all the water that was originally there as water, when it becomes ice, it's like a drumhead. It has a surprising amount of tensile strength. Which is why when it's thing enough you can drive trucks on it.

The water that conducted energy SIDEWAYS is going to be moving fast, maintaining it heat and energy. Frozen ground, lakes, and so forth, that water rushes right over until it hits the sea/ocean/whatever. It's almost like a reverse tsunami.

Samamtha "Carter"

Samantha said...

One other thought that popped into my fron this morning when I woke up was even more elegant in ways.

A small comet or cometary fragment. Contains enough serious matter in side it to leave the appropriate "meteor" fragment data that would be confusing and not particularly revealing, and would contain MORE water than the lake can hold.

On another note, I love reading your blog Zoe, gives the girlgenius geek in me stuff to ponder. Plus it's never boring.