Did an Asteroid Impact Cause an Ancient Tsunami?

NYT ^ | Nov 14 2006 | SANDRA BLAKESLEE

[djf]

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.

[djf]

When I get back online to my high-speed, I'm gonna try to get some satellite images.

[Sen Jack S. Fogbound]

4,800 years ago? Hmmm, that might explain why much of our "civilized" world started by then.

There are reports of previous civilizations older than 6,000 years ago. Such as one city of at least 10,000 years or better ago.

Race memory?

[djf]

Thing is, this isn't like having an 18 mile wide crater on the surface, which by itself would have been a catastrophe beyond description.

This is an 18 mile wide crater AFTER IT HAD TRAVELLED THROUGH 2 MILES OF OCEAN!!

I remember reading something about it raining forty days and forty nights, this sure would do it.

[nitzy]

Bush's fault

[edcoil]

Egypt caused Global Warming - or God did. Take your choice.

[Interesting Times]

Ping.

[lafroste]

Interesting article. It implies that catastrophic cosmic strikes are more frequent than we currently believe. Question: How large of an asteroid is needed to make an 18 mile diameter crater (under 12,500 feet of water)? Anyone know?

[GOPJ]

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.

Well, don't have to spend a lot of time worrying about global warming...

[djf]

Dunno. But after thinking about it, there would be a huge pneumatic effect. Liquid does, after all, in a case like this practically act like a solid. A unbelievable compression wave would travel almost immediately to the ocean floor. Like God had a giant toilet plunger. I'm talking a really, really,really BIG toilet plunger.

Trillions of tons of seawater would be instantly evaporated. I would think they should look for salt layers in the area.

[Blue Jays]

It would be interesting to see a modern artist's interpretation of what that wave must have looked like in the final devastating moments. The roar alone must have been deafening...plus something that tall must have created an enormous wind that preceded it.

[DBrow]

4800 years?

[null and void]

Ancient Crash, Epic Wave

[Mad Dawg]

How large of an asteroid is needed to make an 18 mile diameter crater (under 12,500 feet of water)? Anyone know?

I would say somewhere between "big mother" and "homper-stomper". Of course, a more careful examination of the data might increase the estimate to "Some KIND of homper-stomper, I tell you WHAT" but we'll just have to wait for more information.

[blam]

Ancient Crash, Epic Wave

[null and void]

beat ya!

[djf]

Did a search on "ancient", didn't see it...

[blam]

"There are reports of previous civilizations older than 6,000 years ago. Such as one city of at least 10,000 years or better ago."

Lost Civilisation From 7,500 BC Discovered Off Indian Coast

[null and void]

Yeah. The search function doesn't always work very well.

[blam]

"Did a search on "ancient", didn't see it..."

The more the merrier...I say.

[Skylus]

So is Manhattan about the same size as Clay County, Minnesota, and is the Chrysler tower about the same size as the Needles in Strawberry River, Utah? I hate these parochial comments...

[blam]

Did Asteroids An Comets Turn The Tides Of Civilisation?

[GoodWithBarbarians JustForKaos]

Depends on the speed, size and weight, plus hardness/density. That thing must of been really movin' to go through 12,500 feet of water and then create such a crater.

[UglyinLA]

Wow, this event happened around the same time that the moon first appeared in the night sky.

[Mad_Tom_Rackham]

Well, don't have to spend a lot of time worrying about global warming...

The Libs will. They would be complaining about the pattern on the living room wallpaper while the house was burning down around them.

[ThomasThomas]

Just ask Robert Byrd.

[Mad_Tom_Rackham]

How large of an asteroid is needed to make an 18 mile diameter crater (under 12,500 feet of water)?

About the size of Ted Kennedy or Gerald Nadler traveling under impulse power?

[tongue-tied]

mark for later read...thanks

[Central Scrutiniser]

Of course not, it would have capsized Noah's ark and killed off all the animals of the world.

LOL

Leave no child behind, teach evolution.

[djf]

Wow, that second pic is pretty telling. You can see exactly what happened.

And actually, those types of formations would seem to date it geologically pretty recent. They're probably not gonna last tens or hundreds of millions of years.

[verum ago]

"Astronomers monitor every small space object with an orbit close to the Earth."

No, they don't -- current, generous estimates put us as monitoring around 40% of near earth asteroids large enough to have "severe global consequences"-- we could still easily be blindsided by something that might, say, leave 600 ft chevrons behind.

[ClearCase_guy]

Trillions of tons of seawater would be instantly evaporated.

One of the mysteries of the Great Flood is -- "Where did all that water come from?". I guess it didn't stay in an evaporated state -- it precipitated out.

[blam]

When I saw all those chevrons around England, I thought of this article:

The Dark Ages: Were They Darker Than We Imagined?

[WoofDog123]

"
I remember reading something about it raining forty days and forty nights, this sure would do it."

actually this might be it. the timing would be early enough to fit into other cultures' flood/rain stories (sumeria had one IIRC, and I have read that some indian cultures did as well?), and would certainly put enough water into the atmosphere to drasticly disrupt weather patterns worldwide.

[ASA Vet]

There's no mystery if you believe in magic.

[sailor4321]

For God to throw a rock at us that size must mean that He was really pissed!

[aShepard]

bump for later

[null and void]

That time ocean strike, rain/water.

Next time a dry land strike, fire.

[zot]

Thanks for the ping. I recall reading something about an impact off the southeast coast of Australia that put massive areas of debris many miles inland, including the remains of a Chinese fleet.

[Vasilli22]

bump

[Calvin Locke]

By definition, wouldn't they be decreasing? "...fewer than there was before..." type of deal, the larger one,
"rogue" 'roids, crashing where ever? With in a system of an age such as ours?

One of Art Bell's legitimate guests once said that while SETI was a worthwhile endeavor, they're looking in the
wrong places, that is, crowded systems where cosmic collisions are more likely to occur, and therefore,
wipe out any developed life back to the stone age.

Or at least the to the plow as the most important tool.

[ApplegateRanch]

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.

Good, Gaea! How open minded of them.

At least they have advanced since the days when they flatly refused to believe that rocks really could fall out of the sky.

Some of them still seem quite happy in their arrogance, however...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.

I do believe the man means, "Astronomers monitor every KNOWN small space object...".

[Mad Dawg]

About the size of Ted Kennedy or Gerald Nadler traveling under impulse power?

Impulse power? I always thought of Teddy the Hutt as an alcohol fueled system. Or in the words of "Scotty" Clinton: I've givin' 'hr all she can take, cap'n. She's gonna blow!

No, wait, let me rephrase that.

[pleikumud]

"Well, don't have to spend a lot of time worrying about global warming"

Exactly! "global warming" is political science. Natural events such as Mount St. Helens' eruption have more impact than our styrofoam cups. If the earth's orbit around the sun were to vary just slightly (relative to 93 million miles distance to the sun) we would all be frozen or all be toast. "global warming" is nothing but speculation designed to support a political agenda.

[NYFriend]

My physics is pretty poor. I'm not sure how to figure this out. Water doesn't compress, but it can be displaced, however the displacement would be caused by a pressure wave, and a pressure wave can't travel faster than the speed of sound in that medium, so any energy beyond what it takes to displace water at the speed of sound is translated either into heat or hydraulically into the sea bed, right? I think I've got it, but I skipped physics and mechanics in college.

[djf]

I'm not sure either!! Does what you say mean that if I have a steel rod, say 5 miles long, and I smack the end of it with a sledge, that the far end doesn't move any faster than the sound wave would get there?

Either way, remember the vectors. The force it would take to displace the water and move it horizontally is almost perpendicular to the force of the object hitting the surface of the water (assuming it came down from directly overhead).

One hell of a mess. Not the kind of experiment I would advocate trying.

[NYFriend]

You're right about the vectors, which would also increase the amount of force directed towards the ocean floor.

As for your steel rod, no it's not limited by the speed of sound, because the force from your hammer blow isn't transmitted entirely as a pressure wave, the rid is a solid. Although, I suppose in your example, assuming the mass of the rod and hammer are the same (huge hammer, tiny rod), and I whacked the rod on my end with the hammer moving at twice the speed of sound, and you were standing on your end, I think what would happen is you'd see the rod move at twice the speed of sound (assume no friction, no inertia, and no bending on the part of the rod), you'd hear the sonic boom created by the rod's movement, then you'd both see and hear the rod vibrate due to the hammer strike (that vibration would move at the speed of sound in steel) and then you'd hear the boom from the hammer breaking the sound barrier and the sound of the hammer strike (which would move through the air at the speed of sound).

Again, I think this is what would happen. I'm not schooled in the hard sciences. Someone here can probably sort us both out.

[UCANSEE2]

"How large of an asteroid is needed to make an 18 mile diameter crater (under 12,500 feet of water)? Anyone know?"

It was not UNDER 12,500 feet of water (the area it hit) BEFORE the asteriod hit.

[RightWhale]

If the object can make a crater 18 miles across, the depth of water cover would not be a major factor.

[annie laurie]

Ping