[meteorite-list] WHAT OCCURS IN A LARGE HYPERVELOCITY IMPACT ON AN ICE SHEET?
If it is evidence of an impact, it may have happened during the last ice age,
when the area around Lloydminster was under a huge mass of ice.
Ollen's theory, and he stresses that's "all it is" is a large asteroid hit and
melted the thick ice above the area, likely not even reaching the ground.
[epg - I don't think so. Not for this size of blast.]
http://www.meridianbooster.com/2009/03/18/did-a-massive-meteor-touch-down-here
Sunday, March 22, 2009
Lloydminster Meridian Booster
In the first of my notes to the list, I speculated on the timing of the
beginning of the Holocene Start Impact Event. In this note, I move on to
consider some possible geological evidence, and call attention to an earlier
comment by David Ollen on the mechanics of large hypervelocity impacts onto ice
sheets.
DID A MASSIVE METEOR TOUCH DOWN HERE?
Posted By Graham Mason
Posted 4 days ago
It's just a theory, but it's an interesting one.
David Ollen may have found evidence of a massive impact crater just south of
Kitscoty, but it doesn't look anything like what you might expect.
Instead of a huge hole in the ground, it's a circular plateau about 30
kilometres in diameter, with an inner circle about 12 kilometres in diameter.
With this evaporation, a great weight was lifted from the land and, combined
with the heavy ice still around the impact's circumference, caused the land
under the hole in the ice to rise 50 to 100 feet.
"When you have three-quarters of a mile of ice over an area there's a lot of
pressure there," he said. "That ice is heavy. When you all of a sudden bang it
and evaporate half of it, it takes the pressure off but the pressure is still
on around it.
"If all of a sudden you knock the ice out of the spot, it's going to pop up."
Ollen noticed the anomaly while looking at topography maps to determine
Internet availability for households in the area.
"We are an Internet service provider and we subscribe to a website that has a
topography map on it and we use those maps to tell people whether they can get
access rather than driving all the way to a place and telling them we can't
reach it, said Ollen. "I thought about it for a little while and figured a few
things out over the weekend, I thought I may as well send it to Discover
Magazine and the Booster as well.
"It's a big impact, 30 kilometres across. That's a heck of a big asteroid."
Ollen said he'd be interested in knowing what a professional would have to say
about it.
"I've been a science nut since I was a kid. They used to call me "Anti-matter
Dave" when I was in school," said Ollen. "I've always been interested in
science and archeology and geology and anything to do with science."
"It's just a curiosity, it might be wrong it's just an interesting theory."
*END OF ARTICLE QUOTE*
If this is not the first impact of the Holocene Start Impact Event, or one of
the impacts in it, this geobleme bears the signs of perhaps being generated by
a large hypervelocity impact which must have occurred during the last ice age.
If it is the remains of a volcanic plug, would not the ice sheet would have
scoured it away during it's advance?
If this geobleme was not generated by a comet impact, but instead from an
asteroid impact, then perhaps bits of the impactor lie surrouding the area, and
good hunting, everone.
In either case, it strikes me that the water would cool the plasma and wash the
impactites out of the atmosphere almost immediately, along with any cosmic dust
loading from a comet's debris stream.
Obviously, looking at the water flows of the river drainages should help to
pinpoint the location of any ice sheet impact during the last ice age. Such as
the one the Choctaw remembered.
{Sterling, can you work the numbers for comet impact on an ice sheet, and give
us some rough estimates for force of the impact and the volume of water
released? The range for 1.8 atmpospheres overpressure, the kill zone, would
also be interesting. I think that no one has ever done a proper estimate for
the Meteor Crater kill zone. )
all the best,
Ed
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[meteorite-list] WHAT OCCURS IN A LARGE HYPERVELOCITY IMPACT ON AN ICE SHEET? PART 2
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. __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
[meteorite-list] WHAT OCCURS IN A LARGE HYPERVELOCITY IMPACT ON AN ICE SHEET? PART 3
Hola Listeros - Four 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. Three weeks ago we pointed out a geobleme in Canada that may or may not be associated with the Holocene Start Impact Event. Two weeks ago we returned to consideration of the question of "What occurs in a large hypervelocity impact on an ice sheet?", and traced the water release. This week we take a look at other climatic effects. First off, there was not a persistent atmospheric dust load. The larger mega-fauna survived the Holocene Start Impact Event, only to die from starvation due to the much later impact dust loading ca. 10,850 BCE. As ice appears to have been hit and not the ground, it is to be expected that what would be released would be water, and not dust from the ground. That would leave the dust from the impactor(s), but this would have been precipitated out of the atmosphere by the water vapor released in the impact(s). The best current map of impactites from this cometary encounter may be found here: http://www.uc.edu/news/NR.aspx?id=17831 Which map most likely elides the data from the impacts of several comet fragments, impacts which occurred at different times during the Holocene Start Impact Event. Of course, the initial impacts of the Holocene Start Impact Event would have covered a fair part of the ice sheet with black dust, which would have absorbed sunlight and led to ice melting. Those melting waters, both initial and later, would have led to the further dispersal of the impactite dust. Without further coring and detailed studies, the map of impactites shown above is known a priori to be of very limited use. Which leads us back to consideration of the missing Grondine Minima, which we discussed earlier: "We can see that the last ice age lacked a maxima of cold: http://www.climate4you.com/images/VostokTemp0-42%20BP.gif Let us call this missing minimal temperature the "Grondine Minima". The discontinuity with earlier glacial cycles begins at about the same time as the first spike in neutrons between 20,000-10,000 BP." Global Temperature: http://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.gif http://s90.photobucket.com/user/dhm1353/media/Holocene-1.png.html Since atmospheric dust lading from an ice sheet impact could not account for continued melting, What accounts for the continued ice sheet melt, and the creation of Glacial Lake Agassiz? The best hypothesis we have been able to come up with involves this mechanism: http://www.chesapeakequarterly.net/images/uploads/siteimages/CQ/V12N4/p-7a.png When cold water was released into the Pacific Current, it lead to less warm moist air over the ice sheet. That in turn led to less snow and ice, which led to more sunlight being absorbed, which led to further melting. Later impacts may have released meltwater: see slide 18 here for the timing of meltwater pulses: http://slideplayer.com/slide/2808821/ Especially and carefully note that these are PULSES, and not continuous processes. se also slide 34 for a detailed pollen series for Eastern North America, in particular the data for the Ohio paleoclimates. (For your viewing pleasure - an introduction to isolation and precession: https://www.youtube.com/watch?v=oRdyNn1tB-E&index=1&list=PLmen0eQI4-Lof_GS8Amc9sysdRMrRYzps) good hunting, all - E.P. Grondine Man and Impact in the Americas __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
