[meteorite-list] WHAT OCCURS IN A LARGE HYPERVELOCITY IMPACT ON AN ICE SHEET? PART 2

From: E.P. Grondine <epgrondine_at_meteoritecentral.com>
Date: Fri, 29 May 2015 21:03:56 -0700
Message-ID: <1432958636.52510.YahooMailBasic_at_web125502.mail.ne1.yahoo.com>

Hola Listeros -

Three weeks ago, we pointed out that a major rise in sea levels and a major change in climate occurred well before the dates for what is widely and mistakenly called the Younger Dryas Boundary impact event. Two weeks ago we pointed out a geobleme in Canada that may or may not be associated with the Holocene Start Impact Event.

This week we return to consideration of the question of "What occurs in a large hypervelocity impact on an ice sheet?".

While the answer to this obviously depends on where it hits, it is clear that large amounts of water are released. Thus one might suppose that if one had data on water flows down river drainages during this period, one could determine roughly where a hypervelocity impactor hit.

Now it just so happens that for 3 river drainages, we have that data.

The Drainages:
http://www.nature.com/nature/journal/v464/n7289/images/nature08954-f1.2.jpg

and outflows:
http://www.nature.com/nature/journal/v435/n7042/fig_tab/nature03617_F3.html

One of the reasons we have that data for these outlets is that they
feed into the "Atlantic Conveyor", which is of some concern right now:

http://www.pnas.org/content/109/49/19928/F1.large.jpg

Unfortunately, the flows of the Columbia River and Yukon River, which drain into the Pacific Ocean, are not as well documented. (Based on the amount of research done, one might think that in some peoples' opinions the Pacific Ocean plays no role in global climate.)

Columbia River Outflow Overview:
http://geology.gsapubs.org/content/37/1/95.full

or more precisely this graph of the salinity of the water at the outlfow of the Columbia River (Lopes and Mix):
http://geology.gsapubs.org/content/37/1/79.full.pdf+html

But in performing this back calculation from river flows to impact point(s) one may also expect that water released by a large hypervelocity impact on the ice sheet may also have released enough water to breach the glacial ice dams, and this water contributed to the river flows:

For Glacial Lake Missoula:
http://geology.gsapubs.org/content/12/8/464.full.pdf+html

and for Glacial Lake Bonneville:
http://geology.utah.gov/popular/general-geology/great-salt-lake/commonly-asked-questions-about-utahs-great-salt-lake-lake-bonneville/#toggle-id-4

Now if one looks at the temperature data, one can see the first of the Holocene Start Impact(s) and the outflows occurred substantially before what is defined as the Younger Dryas:
http://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.gif

And what occurs in Ohio (where I am writing from) was that warming occurred first, and then cold again:

http://www.dot.state.oh.us/Divisions/Planning/Environment/training/Context%20Studies/Pollen%20and%20Sedimentary%20Records%20Hebron%20Muskox%20Site%20Licking%20County%20OH.pdf

As you can see from Shane's report, there is a re-cooling which likely coincides with the drainge of Glacial Lake Aggassiz around 10,800 BCE.

(see also "Intensity and Rate of Vegetation and Climatic Change, Linda C.K. Shane, The First Discovery of America, The Ohio Archaeological Council, Columbus, Ohio." if you can find a copy, but note that Shane's 14C dates in it have to be recalibrated.)

good hunting,everyone
E.P.
Received on Sat 30 May 2015 12:03:56 AM PDT