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Old 3rd February 2020, 07:21 AM   #161
lomiller
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Originally Posted by MattNelson View Post

On a different subject, it's sad to see such criticism of the impact hypothesis using words like "conspiracy" by YouTuber Anton Petrov (437K subscribers) in his 2018 video "No, a Comet Didn't Destroy Advanced Civilization 12800 Years Ago" --
https://www.youtube.com/watch?v=iIuR_vKZks4
I won’t even bother debunking the claim that an advanced civilization actually existed 12000 years ago as it’s well into the realm of woo-woo.

The evidence for an impact around that time is mixed. The evidence for it causing extinctions or triggering the Younger Dryas is non-existent and in fact the data rules out an impact as a cause.

The warming in the Younger Dryas was not synchronized between hemispheres. This fits with what you’d expect from a melt-water pulse in the arctic, it does not fit with an impact. Furthermore, the Younger Dryas was just one of many similar events that occurs while the earth is undergoing a de-glaciation. The more reasonable explanation is that all these events have a common cause, probably melt-water pulses.

To summarize:
-there may or may not have been an impact 10-12 KYA but probabaly not
-If there was, it did not cause the cooling of the Younger Dryas
-There certainly was no advanced civilization around to be wiped out by the Younger Dryas.
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Old 3rd February 2020, 07:46 AM   #162
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Originally Posted by lomiller View Post
I won’t even bother debunking the claim that an advanced civilization actually existed 12000 years ago as it’s well into the realm of woo-woo.

The evidence for an impact around that time is mixed. The evidence for it causing extinctions or triggering the Younger Dryas is non-existent and in fact the data rules out an impact as a cause.

The warming in the Younger Dryas was not synchronized between hemispheres. This fits with what you’d expect from a melt-water pulse in the arctic, it does not fit with an impact. Furthermore, the Younger Dryas was just one of many similar events that occurs while the earth is undergoing a de-glaciation. The more reasonable explanation is that all these events have a common cause, probably melt-water pulses.

To summarize:
-there may or may not have been an impact 10-12 KYA but probabaly not
-If there was, it did not cause the cooling of the Younger Dryas
-There certainly was no advanced civilization around to be wiped out by the Younger Dryas.
Could a meltwater pulse be caused by an impact?
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Old 4th February 2020, 01:49 PM   #163
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Originally Posted by Red Baron Farms View Post
Could a meltwater pulse be caused by an impact?
Meltwater pulses are a somewhat regular occurrence during de-glaciation so you don’t need an impact to explain them. To cause something like the younger Dryas you need a partially large one discharging into the arctic, which is less common but not related to a comet or asteroid impact. Conceptually, if there were a pulse that was already primed to occur an impact could trigger it, but by definition we are talking about something that was going to happen whether there was an impact or not.


If all the impact energy went into melting ice an asteroid ~1 mile in diameter could melt the 10000Km^3 of ice required to generate such a meltwater pulse. In practice, I expect something somewhat larger would be needed because not all the energy will go into melting ice. Even with enough thermal energy I think you’d end up vaporizing a smaller volume instead of melting but not vaporizing and area ~ 100Km X 100Km X 1Km deep section of an ice sheet. So it still seems pretty unlikely. The outflow would still need to be into the arctic.

Again though, why do we need the complicated, possibly impossible explanation when we already have a know mechanism that we know about that does exactly the same thing.
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Old 4th February 2020, 02:06 PM   #164
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Originally Posted by lomiller View Post
Meltwater pulses are a somewhat regular occurrence during de-glaciation so you don’t need an impact to explain them. To cause something like the younger Dryas you need a partially large one discharging into the arctic, which is less common but not related to a comet or asteroid impact. Conceptually, if there were a pulse that was already primed to occur an impact could trigger it, but by definition we are talking about something that was going to happen whether there was an impact or not.


If all the impact energy went into melting ice an asteroid ~1 mile in diameter could melt the 10000Km^3 of ice required to generate such a meltwater pulse. In practice, I expect something somewhat larger would be needed because not all the energy will go into melting ice. Even with enough thermal energy I think you’d end up vaporizing a smaller volume instead of melting but not vaporizing and area ~ 100Km X 100Km X 1Km deep section of an ice sheet. So it still seems pretty unlikely. The outflow would still need to be into the arctic.

Again though, why do we need the complicated, possibly impossible explanation when we already have a know mechanism that we know about that does exactly the same thing.
Just hypothetically, would such a pulse from the Greenland glacier impact, if it happened, have entered the arctic?

ETA: I am making no claims here, I am simply asking so I can determine if they are mutually exclusive or not.
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Old 4th February 2020, 03:02 PM   #165
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Originally Posted by Red Baron Farms View Post
Just hypothetically, would such a pulse from the Greenland glacier impact, if it happened, have entered the arctic?
Look at a couple of known pulses.
Meltwater pulse 1A "between 13,500 and 14,700 years ago, during which global sea level rose between 16 meters (52 ft) and 25 meters (82 ft) in about 400–500 years"
Meltwater pulse 1B "between 11,500 and 11,200 years ago at the beginning of the Holocene and after the end of the Younger Dryas" (extent debated but there is one "300-calendar year interval").

They last for centuries and are not the sudden increases in sea-level that an impact on a glacier suggests. So we need to go even more hypothetical - large impact to melt enough ice + something to spread melting over a few centuries + egress of the meltwater to the ocean over that period.

The Greenland impact under the Hiawatha Glacier region cannot account for any recorded pulses because we do not have a date for it. It could be up to 3 million years old.
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Old 4th February 2020, 04:12 PM   #166
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Originally Posted by Reality Check View Post

The Greenland impact under the Hiawatha Glacier region cannot account for any recorded pulses because we do not have a date for it. It could be up to 3 million years old.
Obviously. That's why I asked if it was mutually exclusive or not.

There is a huge difference between, "we cant attribute it to this because we don't know when this happened" and "we can't attribute it to this, because even if it happened at the exact correct time and place, would not have that sort of an effect on the climate system."
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Old 4th February 2020, 05:08 PM   #167
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Originally Posted by Red Baron Farms View Post
Obviously. That's why I asked if it was mutually exclusive or not.
It is what you omitted that makes impact and other causes mutually exclusive - impacts somehow need to melt ice for periods of centuries. That is a reason why the collapse of continental ice sheets is listed as a cause.
So as you wrote "we can't attribute it to this, because even if it happened at the exact correct time and place, would not have that sort of an effect on the climate system. sea levels".

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Old 5th February 2020, 08:16 AM   #168
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Originally Posted by Red Baron Farms View Post
Just hypothetically, would such a pulse from the Greenland glacier impact, if it happened, have entered the arctic?

ETA: I am making no claims here, I am simply asking so I can determine if they are mutually exclusive or not.
“Could have” isn’t relevant to the discussion.
- There is no evidence a meltwater pulse from Greenland at the exact right time and place
- there is not evidence for an asteroid impact at exactly the right time and place,
- It’s questionable as to whether and an asteroid impact would melt that much ice as opposed to vaporizing a much smaller volume.
- There are two solid candidates for when/where the pulse occurred. Neither is in Greenland and neither require any form of asteroid strike.


Astrid strike aside I don't know if a suitable glacial lake in Greenland is plausible, nor do I know for sure if such a lake would be a viable candidate for a suitable pulse of fresh water into the arctic. I do know that Greenland is not part of the discussion in the climate literature. The in the published climate science the debate is between a route up the Mackenzie Valley and another possible route thought the St Lawrence.
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Old 5th February 2020, 08:33 AM   #169
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Originally Posted by Reality Check View Post
Look at a couple of known pulses.
Meltwater pulse 1A "between 13,500 and 14,700 years ago, during which global sea level rose between 16 meters (52 ft) and 25 meters (82 ft) in about 400–500 years"
Meltwater pulse 1B "between 11,500 and 11,200 years ago at the beginning of the Holocene and after the end of the Younger Dryas" (extent debated but there is one "300-calendar year interval").

They last for centuries and are not the sudden increases in sea-level that an impact on a glacier suggests. So we need to go even more hypothetical - large impact to melt enough ice + something to spread melting over a few centuries + egress of the meltwater to the ocean over that period.

The Greenland impact under the Hiawatha Glacier region cannot account for any recorded pulses because we do not have a date for it. It could be up to 3 million years old.


IIRC at the onset of the YD temperatures in Greenland dropped over just a couple decades. This suggests a single event similar (probably larger) than the one that formed the Channeled Scablands in Washington State. In an event like this meltwater accumulates in a glacial lake for hundreds of years, then the ice dam holding it weakens and thousands or tend of thousands of Km^3 of fresh water drain into the ocean over a few days or weeks.

In the case of a YD this would need to drain into the arctic, and the fresh water pushes the point where Gulf Steam sinks into the Atlantic south by 1000 or so miles. This cause almost immediate cooling in Greenland, Western Europe and Eastern North America that is a close match to the pattern seen in the YD.
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Old 7th February 2020, 06:32 PM   #170
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Comet Research Group

https://cometresearchgroup.org/

Scientific publications are listed here: https://cometresearchgroup.org/publications/

9 introductory PDF documents are linked at their "Comets, Diamonds, & Mammoths" page:
https://cometresearchgroup.org/comet...onds-mammoths/
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Old 8th February 2020, 10:32 PM   #171
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I'm sure I've posted this previously, but it can't do any harm to link it again;

The Younger Dryas impact hypothesis: A requiem
Pinter, N. et al. (2011)
https://cosmictusk.com/wp-content/up...-A-requiem.pdf

Having a quick scan through the above found something that had amused me when I'd first read it;

Quote:
Recent studies have shown that carbon spheres and elongates do not represent
extraterrestrial carbon nor impact-induced megafires, but are indistinguishable from fungal sclerotia and
arthropod fecal material that are a small but common component of many terrestrial deposits.
So, not a comet at all, but spider s***!
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