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  #16  
Old 29 Oct 11, 18:11
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Many reading here are likely familiar with the claim that it likely was a small asteroid impacting Earth about 65 million years ago that produced the Extinction Level Event (E.L.E.) that resulted in the dinosaurs (and many other lifeforms) becoming footnotes in geological history. It's been suggested that other E.L.E.s in the fossil record might also have been instigated by an impact event, so this thread topic is one of on-going significance to planetary history, IMO.

In my Opening Post here I provided the following link;
http://abob.libs.uga.edu/bobk/
from which I'll present this QUOTE:
This resource, which began in 1994, is offered as a public service. Though other themes are touched upon, the site is primarily focused on understanding the social and physical influence of a once highly-visible large-comet, in a short-period Earth-threatening orbit. This object, according to astronomical evidence, has been progressively breaking up since the Holocene time period began. The result of such debris scattering was to increase the likelihood of Earth's climate being affected by periodic interaction with extraterrestrial material during this most recent time period.
The subject is fascinating and demonstrably essential to an accurate understanding of our species' behavior over the past 12,000 or so years. Some familiarity with this topic will be seen as necessary by students of anthropology, archeology, classics, and religion who peruse this material objectively. The topic also has philosophic and social policy aspects that need to be explored. As the first species on Earth with the capacity to prevent impact events that would otherwise affect biological evolution--What is our responsibility and what is a prudent course of action?



A recent event connected with the Taurid Stream would be the Tunguska Event or Tunguska Blast of June 30, 1908;
http://en.wikipedia.org/wiki/Tunguska_event
QUOTE:
The Tunguska event, or Tunguska blast or Tunguska explosion, was an enormously powerful explosion that occurred near the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia, at about 7:14 a.m. KRAT (0:14 UT) on June 30 [O.S. June 17], 1908.[1][2][3][3]
The explosion is believed to have been caused by the air burst of a large meteoroid or comet fragment at an altitude of 5–10 kilometres (3–6 mi) above the Earth's surface. Different studies have yielded varying estimates of the object's size, with general agreement that it was a few tens of metres across.[4]
The number of scholarly publications on the problem of the Tunguska explosion since 1908 may be estimated at about 1,000 (mainly in Russian). Many scientists have participated in Tunguska studies, the best-known of them being Leonid Kulik, Yevgeny Krinov, Kirill Florensky, Nikolai Vladimirovich Vasiliev and Wilhelm Fast.[5]
Although the meteoroid or comet burst in the air rather than hitting the surface, this event is still referred to as an impact. Estimates of the energy of the blast range from 5 to as high as 30 megatons of TNT (21–130 PJ),[6][7] with 10–15 megatons of TNT (42–63 PJ) the most likely[7]—roughly equal to the United States' Castle Bravo thermonuclear bomb tested on March 1, 1954, about 1,000 times more powerful than the atomic bomb dropped on Hiroshima, Japan, and about one-third the power of the Tsar Bomba, the largest nuclear weapon ever detonated.[8] The explosion knocked over an estimated 80 million trees covering 2,150 square kilometres (830 sq mi). It is estimated that the shock wave from the blast would have measured 5.0 on the Richter scale. An explosion of this magnitude is capable of destroying a large metropolitan area.[9] This possibility has helped to spark discussion of asteroid deflection strategies.
The Tunguska event is the largest impact event over land in Earth's recent history.[10] Impacts of similar size over remote ocean areas would most likely have gone unnoticed[citation needed][dubiousdiscuss][11] before the advent of global satellite monitoring in the 1960s and 1970s.


~~~~~~~~~~~~~~~~~~~~~~~
Had this occurred a few hours later it would have been over northern Europe and the scale of destruction likely even greater. One can't help but wonder the effect upon the Great War six years later had such an "alternative timeline" event occurred. One also has to wonder the reaction in current times when such a natural event might be thought the use of nuclear device, especially were another such to occur over a populated area/major Nation.


The Tunguska event occurred when the stream is coming at Earth from the direction of the Sun, hence making astronomical observation and warning, back then, near impossible. We've a slightly improved situation today, given some of the sats and observatories in use, but from from a "failsafe" situation. The first two weeks of November are when we'll next transit the Stream, this will be visible at night and likely increase the average number of meteors seen if the skies are clear.


Another event likely related to the Taurid Stream is the source of the Carolina Bays which may have coincided with the end of the last "Ice Age" and attendant species extinctions then. I'll get to that one later. It's dry outside and I've a few hours of daylight left to attend some yard and shed-building activities.
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  #17  
Old 07 Nov 11, 18:07
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How to save Earth from a killer asteroid
QUOTE:
A huge asteroid's close approach to Earth Tuesday reinforces that we live in a cosmic shooting gallery, and we can't just sit around waiting to get hit again, experts say.

Asteroid 2005 YU55, which is the size of an aircraft carrier, will zip within the moon's orbit tomorrow, but it poses no danger of hitting us for the foreseeable future. Eventually, however, one of its big space rock cousins will barrel straight toward Earth, as asteroids have done millions of times throughout our planet's history.

If we want to avoid going the way of the dinosaurs, which were wiped out by an asteroid strike 65 million years ago, we're going to have to deflect a killer space rock someday, researchers say. Fortunately, we know how to do it.

"We have the capability — physically, technically — to protect the Earth from asteroid impacts," said former astronaut Rusty Schweickart, chairman of the B612 Foundation, a group dedicated to predicting and preventing catastrophic asteroid strikes. "We are now able to very slightly and subtly reshape the solar system in order to enhance human survival."

In fact, we have several different techniques at our disposal to nudge killer asteroids away from Earth. Here's a brief rundown of the possible arrows in our planetary defense quiver.

http://www.msnbc.msn.com/id/45192148...ller-asteroid/

(EDIT to include article title and enhance readability.)

Last edited by G David Bock; 07 Nov 11 at 21:40..
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  #18  
Old 07 Nov 11, 18:38
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Apart from the K-T extinction, there's no actual evidence of other impact-related major extinction events. And even the K-T extinction's cosmic cause is in doubt. The massive flood basalt eruptions that formed the Deccan Traps formation probably did more to kill off the dinosaurs than the Chixclub impact event. Major flood basalt eruptions are highly correlated with mass extinction events over the last 250 MY; impact events are not.

The evidence for the end-Pleistocene extinctions being impact-related is extremely weak. The only major distinction between the transition from the Pleistocene to the Holocene and the previous glacial-interglacial transitions was the migration of humans out of Africa, across the world and the demise of most of the mega fauna that were in the path of that migration…



YU55 would devastate whatever area it hit; but would cause very little damage beyond about a 75 mile radius. The Tunguska blast would have also been catastrophic if it had hit a populated area.

NEO's are a hazard and more should be done to track them and develop defensive measures... But the ELE aspect has been exaggerated in the popular media.

Last edited by The Doctor; 07 Nov 11 at 18:57..
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Old 07 Nov 11, 21:58
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Yeah I saw a fairly good program in the past week or so describing the problems with the impact the primary cause of the extinction. Lots of other bad things going on at the same time.

Cold comfort though as our civilization is probably a lot more fragile than the Earth's ecosystems. Life may well get on quite well after a big impact but but have grave doubts that our technological achievements would survive as other than a new class of 'fossils'.
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Old 07 Nov 11, 22:04
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Well Doc,

The size/mass threshold for E.L.E. Impacts is usually about a mile or greater in diameter, but mass/density is a factor. Solid rock asteroid likely to do more damage than loose aggregate comet object of equal sizes. And, of course, the more over that @ one mile diameter size, the greater potential to affect more of the Earth.

It's not just the impact alone, but also what effects it produces with the Earth's geology and/or hydrosphere. A one mile+ sized object hitting the ocean would set off quite the tsunami. Enough speed and mass added in for punching into the Earth's crust and it could also chain off earthquakes and volcanic eruptions, perhaps even those "Major flood basalt eruptions", and these 'secondary effects' could readily mask the impact that started the 'chain reaction' going.

Quoting from one of your links;
" ...It is also worth mentioning that some flood basalts (e.g. the Parana) do not match with any indicators of serious system stress, and some small mass extinctions do not appear to correspond with any flood basalts. This may be because it is unlikely that there is one single cause for all mass extinctions."
http://www.le.ac.uk/gl/ads/SiberianTraps/FBandME.html

From my studies of the subject, a large enough object Impact is bad enough, it's the prospect of those secondary effects that add real injury to insult.

As for this:
QUOTE:
" The evidence for the end-Pleistocene extinctions being impact-related is extremely weak. The only major distinction between the transition from the Pleistocene to the Holocene and the previous glacial-interglacial transitions was the migration of humans out of Africa, across the world and the demise of most of the mega fauna that were in the path of that migration…"

Less see, 1-2 million humans, max global population, whom could barely chip flint into workable spear points, wiped out scores of species of large fauna, like mammoths, mastadons and sabre-toothed tigers???!!! Intriguing how they managed also to "quick-freeze" some of their victims.
Then there are the dozens of large deposits of skeletons in Alaska, Siberia, and other parts of the globe where we find tropical, temperate, and tundra species all mingled together, bones splinted, skeletal structures intermingled. Just tip of an iceberg of evidence that suggests something more on the lines of global cataclysmic event(s) which might have been triggered by Impact(s).

I'll try to flesh (pun intended) this concept out later when have more time, but it might be more a topic for another thread title.
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Old 07 Nov 11, 22:57
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Here's a toy...

http://neo.jpl.nasa.gov/

Play with it for a hour...

http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2011%20UF10;orb=1
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Old 07 Nov 11, 23:47
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Quote:
Originally Posted by G David Bock View Post
Well Doc,

The size/mass threshold for E.L.E. Impacts is usually about a mile or greater in diameter, but mass/density is a factor. Solid rock asteroid likely to do more damage than loose aggregate comet object of equal sizes. And, of course, the more over that @ one mile diameter size, the greater potential to affect more of the Earth.

It's not just the impact alone, but also what effects it produces with the Earth's geology and/or hydrosphere. A one mile+ sized object hitting the ocean would set off quite the tsunami. Enough speed and mass added in for punching into the Earth's crust and it could also chain off earthquakes and volcanic eruptions, perhaps even those "Major flood basalt eruptions", and these 'secondary effects' could readily mask the impact that started the 'chain reaction' going.
There's just very little evidence for impacts of that size over the last 300 MY. Whereas the flood basalts are clearly documented with known mass extinctions.

Quote:
Originally Posted by G David Bock
Quoting from one of your links;
" ...It is also worth mentioning that some flood basalts (e.g. the Parana) do not match with any indicators of serious system stress, and some small mass extinctions do not appear to correspond with any flood basalts. This may be because it is unlikely that there is one single cause for all mass extinctions."
http://www.le.ac.uk/gl/ads/SiberianTraps/FBandME.html
I didn't say that all flood basalts were correlated with all extinctions. They are simply highly correlated. The strong correlation between extinctions and impacts starts and ends at the K-T.

Quote:
Originally Posted by G David Bock
]From my studies of the subject, a large enough object Impact is bad enough, it's the prospect of those secondary effects that add real injury to insult.

As for this:
QUOTE:
" The evidence for the end-Pleistocene extinctions being impact-related is extremely weak. The only major distinction between the transition from the Pleistocene to the Holocene and the previous glacial-interglacial transitions was the migration of humans out of Africa, across the world and the demise of most of the mega fauna that were in the path of that migration…"

Less see, 1-2 million humans, max global population, whom could barely chip flint into workable spear points, wiped out scores of species of large fauna, like mammoths, mastadons and sabre-toothed tigers???!!! Intriguing how they managed also to "quick-freeze" some of their victims.
Then there are the dozens of large deposits of skeletons in Alaska, Siberia, and other parts of the globe where we find tropical, temperate, and tundra species all mingled together, bones splinted, skeletal structures intermingled. Just tip of an iceberg of evidence that suggests something more on the lines of global cataclysmic event(s) which might have been triggered by Impact(s).

I'll try to flesh (pun intended) this concept out later when have more time, but it might be more a topic for another thread title.
The megafauna of Africa and South Asia evolved with humans and had time & space to get out of the way. During the Pleistocene-Holocene transition, atmospheric CO2 levels rose rapidly and grasslands in the mid latitudes rapidly became forested. Most of the megafauna herbivores were adapted to grasslands. The combination of the sudden influx of humans & dogs, habitat infringement and new flea-born diseases were probably overwhelming. The megafauna predators were out-competed.

The only thing that differentiates the Holocene from previous Pleistocene interglacial stages is modern man.
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Old 08 Nov 11, 12:55
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Quote:
Originally Posted by The Doctor View Post

The only thing that differentiates the Holocene from previous Pleistocene interglacial stages is modern man.
Don't forget those Sub-Zero freezers they must have been toting around! It's not easy to flash-freeze an entire herd of mammoths - the hard part is carrying a long enough extension cords to reach all the way forward to the 1800's to find a plug-in...

The Earth is pock-marked with huge impact craters, and it's naive beyond belief to think that none of these impacts had any effect on the flora and fauna of the times, or that Prehistoric Man was capable of wiping out millions and millions of large mammals.

Which evolved first - the flea or the dog? Careful...


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Old 09 Nov 11, 01:45
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Some images of YU55;
http://cosmiclog.msnbc.msn.com/_news...puts-on-a-show
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Old 17 Nov 11, 12:25
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Asteroid debate rises to next level

By Alan Boyle
As of now, there's no comet or asteroid that's definitely due to smash into our planet, but experts say it's high time to figure out how to deal with the uncertainties, misunderstandings and political wrangling that will inevitably arise during the asteroid alerts to come.
Last week's hubbub over the asteroid 2005 YU55, which passed within 200,000 miles of Earth, set the scene for a seminar on near-Earth objects sponsored in Boulder, Colo., by the Secure World Foundation. The public's interest in the harmless flyby was just a foretaste of what could happen when astronomers spot a rock that has a significant chance of hitting Earth.
And it is a question of "when," rather than "if."
Several potential impacts have been flagged over the past decade. In most of those cases, further observations — including observations gained from "pre-discovery" images of the objects in question — have ruled out a collision.
http://cosmiclog.msnbc.msn.com/_news...-to-next-level
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Old 17 Nov 11, 15:12
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Quote:
Originally Posted by Bwaha View Post
Jpl neo. Fun toy...

http://neo.jpl.nasa.gov/neo/

Play with it...
Playmate;
http://impact.ese.ic.ac.uk/ImpactEffects/
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Old 21 Nov 11, 16:43
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Actually, I like that Purdue/Imperial College tool; a lot of fun seeing what might happen.....rough effects of course but pretty much reflects what my old military history teacher said about being on the receiving end of a nuclear strike : ' the best protection is distance'.
The interesting thing is that while, at short distances, the earthquakes can be quite destructive to buildings, the mention of secondary effects of ejecta is not really mentioned. So, if you look closely, you'll see that ejecta sizes can be quite large but they don't show what kind of damage you'll get. For instance, I put in a 1 Km iron object at 90 degrees with a distance of 100 Km, the average ejecta size is 2.55 m with average fragment diameters of 22-3 cm. That's going hurt if you get 1 large piece and 1 fragment, much less anything in between.

Last edited by boomer400; 21 Nov 11 at 16:51..
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Old 21 Nov 11, 17:44
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Originally Posted by boomer400 View Post
Actually, I like that Purdue/Imperial College tool; a lot of fun seeing what might happen.....rough effects of course but pretty much reflects what my old military history teacher said about being on the receiving end of a nuclear strike : ' the best protection is distance'.
The interesting thing is that while, at short distances, the earthquakes can be quite destructive to buildings, the mention of secondary effects of ejecta is not really mentioned. So, if you look closely, you'll see that ejecta sizes can be quite large but they don't show what kind of damage you'll get. For instance, I put in a 1 Km iron object at 90 degrees with a distance of 100 Km, the average ejecta size is 2.55 m with average fragment diameters of 22-3 cm. That's going hurt if you get 1 large piece and 1 fragment, much less anything in between.
At Barringer Crater, they have interactive, animated simulators... Fun stuff!
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Old 21 Nov 11, 18:30
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Originally Posted by G David Bock View Post
It's not just the impact alone, but also what effects it produces with the Earth's geology and/or hydrosphere. A one mile+ sized object hitting the ocean would set off quite the tsunami. Enough speed and mass added in for punching into the Earth's crust and it could also chain off earthquakes and volcanic eruptions, perhaps even those "Major flood basalt eruptions", and these 'secondary effects' could readily mask the impact that started the 'chain reaction' going.
Don't forget the 40 days and nights of rain following the ocean impact. Cubic miles of water/steam will be ejected into low Earth orbit. Then it will come back as rain, rain, rain. The environmental effects of flooding every river in the world simultaneously, for a month, would be devastating.

Conveniently for Mother Nature, we build all our major cities next to rivers, lakes, and the ocean where they are most vulnerable to such an event. Likewise, all the crops would fail so massive famine would follow in the wake of the initial impact disaster.

It's not a matter of "if", it's just a matter of when in the past, and when in the future we will get the cosmic slap down again.
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Old 21 Nov 11, 20:07
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"It's not a matter of "if", it's just a matter of when in the past, and when in the future we will get the cosmic slap down again."

Yep. I like the idea of capturing asteroids and using them for the materials for space colonies...

http://www.nss.org/settlement/Coloni...ace/index.html

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