Paper on Comet/Asteroid Impact Causing the Younger Dryas Cooling.

[The Grand Nudger]

And again - it's not as though the proponents don't point to craters. They simply point to craters which are smaller than what detractors would demand. I'm on the fence on this one, personally. I don't think that the propoents have presented anything knockdown..but at the same time the dtractors have not presented anything that would explain such spherules.

Simultaneous coal seam fires along a fairly simple trajectory?...Cmon now guys..try harder.

[pocaracas]

~2/3rds of the planet's surface are water... could it have... hit the water?

[The Grand Nudger]

While identifying submersed impact craters has become much easier of late, dating them is still difficult and prohibitively expensive. That's why a canary island subduction -while plausible- does not provide definitive evidence of such an impact.

On the one hand it's very reasonable to say that a significant portion of the story of our planets history is currently underwater.....on the other, it's very difficult to establish any specifics about what is or is not underwater.

[Anomalocaris]

~2/3rds of the planet's surface are water... could it have... hit the water?

They should be able to map the strewn field and propose a location for the impact and see if it under water or not.

Reguardless of whether it is underwater or on land, if a large crater is indeed associated with young dryas event, that crater would be the youngest, and thus the most prestine and least eroded, most conspicuous large crater we ever found, provided we know where to look.

If the propose point of impact is indeed under water, it would introduce more room for falsifiable predictions and bounding constraints. For example, impacts in deep ocean would tend to inhibit the formation of strewn fields, so if iproponent thinks it hit deep sea and still made an enormous strewn field, then the lower limit on its size would increase dramatically. Now we expect an object not hundred of meters across but kilometers across. We would also expect to see megatsunami deposites on all adjacent shores from impact of such a massive object.

[Minimalist]

So where is the crater?

Firestone's idea is that whatever it was hit the glacier and would have made a huge crater....which subsequently melted. The glaciers got as far south as the Ohio River. Plenty of room for it.

[The Grand Nudger]

Laurentide impact adds a layer of what could only be called a deplorable lack of potential falsification. It's not so much of an issue that it couldn't have occurred, as that we cannot establish that it did, and ways to establish that it did not are limited.

[Minimalist]

The glacier did exist, though.





Unlike the garden of "Eden."

[The Grand Nudger]

lol, granted, it's more plausible than "eden".

[Anomalocaris]

So where is the crater?

Firestone's idea is that whatever it was hit the glacier and would have made a huge crater....which subsequently melted. The glaciers got as far south as the Ohio River. Plenty of room for it.

Unlike the bible and Eden, Even such a flippant dodge as an ice crater still dignifies itself with some falsifiable predictions:

1. An impactor 400-500 meters across would fracture and generate impact brecciation 2-3 miles into hardrock and thus would leave a pretty spectacular impression even under a mile of ice. So if the theory requires the crater didn't penetrate the ice sheet, than it predicts the impactor wasn't large enough to generate 50 million tons of spheriules from its own mass.

2. Where did the spheriules come from? The theory claimed the spheriules are similar to "known impact materials derived from surficial sediments melted at temperatures 2,200 °C". That would be hard to explain if there would still be ice between the impact and the surficial sediment, which would presumable keep surface material well under 2200 degrees centigrade, and more or less rooted in place instead of being strewn over 4 continents.

It's nice to try justify a theory using an ad hoc claim that invalidates the reason why the theory was postulated in the first place.

Where it not for the falsifiable predictions that accidentally slipped in, the ice crater hypothesis would be prideworthy chutzpah of almost, but not quite, new testamental proportions.

[Minimalist]

From their conclusion...Page 9.

The nature of the impactor remains unclear, although we suggest that the most likely hypothesis is that of multiple airbursts/impacts by a large comet or asteroid that fragmented in solar orbit, as is common for nearly all comets. The YD impact at 12.8 ka is coincidental with major environmental events, including abrupt cooling at the YD onset,major extinction of some end-Pleistocene megafauna, disappearance of Clovis cultural traditions, widespread biomass burning, and often, the deposition of dark, carbon-rich sediments(black mat). It is reasonable to hypothesize a relationship be-tween these events and the YDB impact, although much work remains to understand the causal mechanisms

The climate did change and the megafauna did go extinct. Moreover, Clovis artifacts are present below the YDB but not above. I don't like coincidences. They make my balls itch.