Ancient Crash, Epic Wave

avtchillsboro writes "A NY Times article says that scientists have discovered evidence a massive impact crater 18 miles in diameter and 12,500 feet under the Indian Ocean. The evidence, they say, consists of four massive chevron-shaped sediment deposits on the island of Madagascar. '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.' Interestingly, the scientists say that the currently accepted notion that there have been no major impacts in the last 10,000 years is wrong; and that major impacts occur on average every 1,000 years, rather than the currently accepted 500,000 to 1,000,000 year interval. '(T)he 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.'"

Comments

Ancient crash?

[LiquidCoooled]

Does that mean Microsoft was behind the blue wave of death?

I thought it sounded familiar

[smooth wombat]

And then I realized, it's from 6 days ago when I posted the exact same story in my journal. On top of which I had also checked it off to be a possible story and the editors of course rejected it.

Slashdot, where the news is stale, the editors don't edit and geeks still can't get a girlfriend.

Interesting methods, troubling results

[zeropointburn]

This is somewhat troubling. Before these people went looking, we assumed we had somewhere between now and 10,000 AD or so before the next major impact. (mangling the fine art of statistics, I know) Now, they're saying it could be a thousand years or less between impacts. When was the last major impact? We could be due for a serious catastrophe in very short order, practically instantaneous in geological terms.
I'm certainly not reassured by the fact that we only monitor about 3% of the sky. Sure, we think we know about every significant object that approaches Earth, but that doesn't account for rogue objects (those with either highly elliptical or hyperbolic orbits, or extrasolar objects that can't currently be tracked or predicted). Since FEMA is basically shite and lunar exploration/colonization is basically all hype at this point, what the hell are we going to do if we find out tomorrow that the world as we know it will shortly end?

Tinfoil hats aside, there's some excellent insight into scanning technology presented in the article. The idea of precisely scanning sea surface height to identify local gravitational variations interests me greatly. Just think about that for a little bit; let the sheer coolness of such remarkable precision sink in. It's also interesting to note that miles-wide craters have escaped our notice for millenia. Props for taking the obvious route and playing connect-the-dots with geological formations.
Of course, the doubt is strong already amongst the established scientific community. I'd say that since they've already done sediment tests for several sites and identified tektites neatly fused with diatoms (meteor debris melted to fossil plants), it's pretty clear that their methods are valid and are producing reliable results.
The note at the end of TFA about using Flood myths to date and place a major impact is particularly intriguing. Some of the 'researchers' that have taken the route of aggregate myth analysis have come up with some pretty questionable results, but in other cases, surprising correlations stand out. Consider that virtually every culture, living or dead, has a flood myth in some form or another. I think it's good for us all to be reminded that myths and legends are based on real people and events, however obsured by the ravages of time and creative retelling.
That's all I've got...

Re:Interesting methods, troubling results

[Dunbal]

what the hell are we going to do if we find out tomorrow that the world as we know it will shortly end?

Die?

Consider that virtually every culture, living or dead, has a flood myth in some form or another. I think it's good for us all to be reminded that myths and legends are based on real people and events, however obsured by the ravages of time and creative retelling.

      Since human life is pretty strongly interrelated with water, and most of our communities have to be near water (with few exceptions), it's not surprising that there are flood myths. The source of these myths don't have to be global catastrophes however. Just the occasional river flood, or storm, could be enough to reinforce the idea of flooding as something bad. Then some creative soul exaggerates "that flood we had 20 years ago" and the flood myth is born.

      Remember if we're talking huge tidal waves from a large meteor impact, the people who witness this wave (albeit briefly) are quite unlikely to survive long enough to tell others about it.

Re:Interesting methods, troubling results

[zeropointburn]

Remember if we're talking huge tidal waves from a large meteor impact, the people who witness this wave (albeit briefly) are quite unlikely to survive long enough to tell others about it.
Yes and no... There are places where mountain chains run right into the ocean, for starters. A few people could have survived. Besides, people who lived far enough away from shore, or high enough to avoid the surge, would have been able to see the devastation long after the event. If you were to go to New Orleans today, you'd see evidence of the devastation wrought by the (somewhat) recent hurricanes. A megatsunami would leave permanent scars; coastlines would be reformed, low-lying vegetation wiped away, the courses of rivers changed, etc. People would eventually find out, and the scars on the land wouldn't fade for decades, if not centuries. For that matter, if we looked closely enough, we could probably find fairly convincing evidence for this megatsunami scenario having actually happened several thousand years ago anywhere we care to look (within reason).

Of course, that does not disprove the fact you've pointed out, namely that early humanity was tied very closely to water. Floods were locally devastating events that remained in the cultural consciousness for many generations, often growing in the retelling. The prime difficulty faced by researchers investigating the factual basis of myths is, in fact, picking out the little bits of truth from all the embellishments.

As for dying, should a large impact occur, you're exactly right. We'll be dying by the billions. All the preparation in the world would be meaningless if a hefty chunk of rock were to impact anywhere near you at a few kilometers per second. The only realistic means of preserving humanity in such an event would be successfully, sustainably establishing a permanent human presence in space before it all went down. Not a few people in a space station, but thousands or more wherever we can make it work. For those of you against colonization for financial reasons, I'm not advocating devoting our entire world production to this. It doesn't make sense to place all of your eggs in the same basket. We should be putting serious effort into many areas of improvement, space colonization among them.

Re:Interesting methods, troubling results

[zeropointburn]

I stand corrected.
You're absolutely right: a 10-megaton impact would be quite surviveable for the majority of humans. Certainly locally catastrophic, but bomb shelters and the like would be useful down to some distance from impact (based on size, density, velocity, and material at impact, as well as shelter design). I did specify 'large impact', but it was in the context of the article, so that would equate to about 10 megatons.
This would help explain how they came up with the 1,000 year per impact number as opposed to the .5 million year per impact number. Their definition of 'major' apparently differs... of course, it may be that they can find evidence from much smaller impacts underwater due to this gravitational scanning technology than are observable on land after x thousands of years of erosion. Since smaller impacts presumably happen more often, that would make the rate of 10-megaton impacts much faster than that of 1,000 megaton impacts, for instance.

Re:Interesting methods, troubling results

[Dunbal]

Of the dozens of films, none come from areas where the waves were 20 feet or higher,

      Don't think of a tsunami as a traditional wave - it's not. It's a wave with an EXTREMELY long wavelength, in the km range. So from your perspective it will just look like the ocean decides to come inland. The water level rises suddenly, and keeps rising. Don't look for a "crest", there won't be one. Just water coming inland constantly, and knocking everything down. Then the "wave" recedes, because once the energy is spent, well, we all know water likes to flow downhill...

New SI units

[Dunbal]

Each covers twice the area of Manhattan with sediment as deep as the Chrysler Building is high.

      Can anyone help me with the conversion here? How many football fields to a Chrysler Building, and how many cubic libraries of congress to a Manhattan? Sheesh whatever happened to things like meters, or even feet?

Re:New SI units

[mrjb]

Turns out it is 1.58573928 furlongs high.

Re:New SI units

[Red Flayer]

How many football fields to a Chrysler Building

With or without the endzones?

how many cubic libraries of congress to a Manhattan?

Huh? That's just apples and oranges, my friend. LoCs are a measurement of data capacity, not physical volume. Besides, the "area of Manhattan" is two-dimensional, not a cubic measurement.

It's all well and good to ask for measurements in standard units like an LoC, but let's make sure we use them correctly.

The correct answer would be 3.487 football fields (sans endzones) high over two Manhattans, or 8,086,748.43 hogsheads. Was that so hard?

Ooops you went too far.

[tgd]

Insulting Slashdot is a good way to get modded up, but pointing out the lack of girlfriends is going to swing the moderators the other direction!

N00b mistake...

You always comment on the staleness of news, then insult Zonk, make a side quip about dupes and leave the girlfriend angle out.

Thats the secret to high karma!

Written history

[Dan East]

This happened only 4,800 years ago. The impact would have had global repercussions, so shouldn't it be reflected in written history, like in Egypt?

Dan East

Re:Written history

[Anonymous Coward]

4,800 years ago would be Pre-dynastic Eygpt, so it'd be better looking elsewhere, maybe mesopotamia?

Re:Written history

[dreamchaser]

You mean like the Great Flood stories shared by most ancient civilizations?

How deep?

[mrjb]

"with sediment as deep as the Chrysler Building is high" Sorry- can someone convert that to furlongs?

See it in context thanks to Google Maps

[Anonymous Coward]

If you're interested in looking at the Google Earth view of the features mentioned in the article, look here.

Be sure to look up and down the coast on either side of this particular feature.

Lots of water

[CmdrGravy]

I'm surprised these people seem to be the first to start looking for impact craters in the Ocean, being as it covers 3/4 of the globe it stands to reason that 3/4 of all impacts are going to end up in the Ocean somewhere. Maybe it's just a case of only having the necessary technology available fairly recently but I think we ought to be doing everything we can to understand how often and how much damage asteroid strikes occur and can inflict.

Also the size of the Tsunami which created those chevrons must have been almost unimaginably huge but again its likely that for every impact of that size there would have been a lot more which haven't left such obvious signs but would still have been capable of inflicting similar destruction on coastal communities as the Indonesian Tsunami did a few years ago.

Although I think traditional science is a better method of investigating these sorts of incidents I think the idea of tracing back through myths and stories to reach an actual point in time where some group of people actually experienced the event is fascinating. Whether it's just wishful thinking or not and can ever be tied down this precisely is I think questionable.

Any event which caused waves of that size is pretty clearly going to make a big impression on anyone who witnessed any of its effects and would certainly have been talked about for a very long time but whether we can detect any of the story as it must have been originally told is, in my opinion, extremely unlikely.

Re:Lots of water

[Remus Shepherd]

Most researchers never bothered looking for deep ocean impact craters because they assumed the craters would be covered in sediment. In fact, they probably *are* covered in sediment, and it's only because of the new gravimetric technology that we can see them at all.

Another picture of the chevrons is here. Features like this are visible all over the world, as the graphic accompanying the NYT article shows. Pretty spooky...I just never realized before how much scar tissue the Earth has on her.

You can check out the chevrons on Google Maps

[bestinshow]

They're at the south end of Madagascar. Worth a look, in fact at first glance a lot of the south-eastern coast looks like it is showing signs of where a tsunami washed inland a lot, but the chevrons are very clear when you find them. Also there appear to be some more chevrons at the top end of the country, at a different angle, but it's not my line of expertise so I may be wrong.

However it is a neat method of finding recent oceanic meteorite impacts. I don't know how long the chevrons would last - the bigger the impact the longer they'd last seems like an obvious insight though, and 600ft high chevrons would take a very long time to erode, ice ages notwithstanding.

Interesting research, but ...

[Mostly a lurker]

... I find it difficult to understand how failure to account before for ocean impacts of meteors could change the anticipated frequency of large meteor impacts from once every 500,000-1,000,000 years to once every 1,000. Surely, a frequency of once every 1,000 years or so would mean several hundred hitting land every million years. Those would, one imagines, leave pretty obvious evidence.

Re:bad for all the fundies and the atheists

[zeropointburn]

Zecharia Sitchin has some interesting things to say about this very subject. I don't agree with everything he concludes, but the evidence he's dug up is most intriguing.
To be honest, I don't have a definite opinion on the subject of alien visitations. I haven't seen any solid evidence with my own eyes, but I've also never seen any counterevidence. On a theoretical basis, the thought that this is the only inhabited planet in the universe is a flat impossibility.
As for the fundies, denying scientific evidence that runs counter to your beliefs is just burying your head in the sand. It encourages further breaks from reality and lays the foundation for erratic, even psychotic, behavior.
I do, however, agree with you that there have been older civilizations far more advanced than we currently consider. It's like a tip-of-the-iceberg situation, much like the oceanic crater issue. We get these subtle hints and clues, both from the archaeological record and from our own most ancient myths and legends. Never a whole and complete site or city, though, demonstrating precisely what level of understanding was available. It's rather frustrating not to know the legacy of those who came before us.

Tsunami "expert" Ted Bryant

[Spalti]

After RTFA, I found out Ted Bryant is the Tsunami expert in this group of researchers. While researching for my thesis, I was confronted with his book, "Tsunami: the underrated hazard". This work, while being quite easy to understand, can hardly be called scientific based on his way of making citations (grouping all references at the beginning of a chapter which leaves you without the possibility to look up where he drew his conclusions from).

Reviews of his book can be found here: http://hol.sagepub.com/cgi/reprint/12/5/637 and here http://dx.doi.org/10.1016/S0025-3227(03)00086-0 and here: Synolakis, C.E., and G.J. Fryer, 2001. Book Review: Tsunami: the underrated hazard by Edward Bryant, Eos, Trans. Am. Geophys. Union, 82, 588 (can't find a quick link right now).

The existence of so-called megatsunamis is hardly scientifically proven, especially not by the work of Bryant (he classified sedimentary features embedded in sandstone somewhere in Australia as relics of an ancient megatsunami when in a nearby graveyard the same sandstone wouldn't resist local climate and erosion for more than a few centuries).

The propagation of tsunamis with huge waveheights seems to be limited due to dispersion effects and the so-called "Van-Dorn-Effect" should cause these huge waves to break as soon as they reach the continental shelf (http://www.agu.org/pubs/crossref/2005/2004GL02191 8.shtml and http://www.lpl.arizona.edu/~jmelosh/ImpactTsunami. pdf , but also http://www.spaceref.com/news/viewpr.html?pid=10986 ).

After working some time in the field of megatsunamis (my thesis concentrated on the Cumbre Vieja Scenario postulated by Ward&Day back in 2001 (http://www.es.ucsc.edu/~ward/papers/La_Palma_grl. pdf) and, based on scientific grounds, I had to "debunk" it as several researchers have done before me), I have learned to take these reports with a grain (or better, a big portion) of salt.