[meteorite-list] Comets and eskers and drumlins - Oh my!

Wed Apr 7 15:41:34 EDT 2010

Hi, Bob, List,

For further references that illuminate the
origins of this theory, I suggest you glance
at a copy of Classic Illustrated Comic Number
149 -- "Off On A Comet" by Jules Verne,
which explicates the theory in greater
technical detail.

For researchers willing to tackle the source
materials without the comic book pictures:
http://www.gutenberg.org/etext/1353

Myself, I like the comic book version better.

Sterling K. Webb
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----- Original Message ----- 
From: "Robert Verish" <bolidechaser at yahoo.com>
To: "Meteorite-list Meteoritecentral" 
<meteorite-list at meteoritecentral.com>
Sent: Wednesday, April 07, 2010 9:32 AM
Subject: [meteorite-list] Comets and eskers and drumlins - Oh my!

> The following is a review of a bizarre theory that comets are involved 
> in the formation of eskers and drumlins.  -- Bob V.
>
> --------------------------------
> Wednesday, April 7, 2010 5:12 AM
> From:  "Technology Review Feed - arXiv blog" <howdy at arxivblog.com>
>
> the physics arXiv blog
>
>
> Could A Comet Tail Have Scarred the Earth in the Recent Past?
>
> Posted: 06 Apr 2010 09:10 PM PDT
>
> The idea that the Earth shows signs of having repeatedly passed 
> through the tail of a comet does not bear up to scrutiny.
>
> One of the puzzles that geologists occasionally ponder is the nature 
> of eskers and drumlins.
>
> Eskers are winding ridges a few tens of metres high that look 
> remarkably like railway embankments. Indeed they are often used as 
> readymade roads and run up and down hills over distances that 
> sometimes stretch to hundreds kilometres.
>
> Drumlins, on the other hand, are tear drop-shaped hills a few tens of 
> metres high and a hundreds of metres long. They often appear in large 
> numbers with the same orientation in drumlin fields .
>
> Geologists have long assumed that eskers and drumlins are formed by 
> glaciers and left behind after these ice giants retreated.
>
> There are essentially two problems. The first is the internal 
> structure of these formations. Eskers and drumlins have have an outer 
> layer of water-borne clay and silt with attendant fossil debris. This 
> covers an inner core made of unsorted boulders and rocks which are 
> entirely free of fossils. These inner cores do not appear to have been 
> affected by the action of water. How does this structure arise?
>
> The second is that if glaciers are responsible for eskers and 
> drumlins, they ought to be forming now. And yet nobody can find 
> anywhere on Earth where these structures are currently forming.
>
> Today, Milton Zysman and Frank Wallace publish on the arXiv their 
> explanation for the formation of these objects and it makes for 
> fascinating, if not entirely convincing, reading.
>
> Zysman and Wallace say that eskers and drumlins are the debris left on 
> Earth after our planet repeatedly passed through the tail of a giant 
> comet. They say this explains the distribution of eskers and drumlins, 
> which often form in roughly parallel lines.
>
> It also explains their internal structure. The rocky core of these 
> objects is pure cometry debris which explains the absence of fossils. 
> The outer layer built up later through the action of water and ice.
>
> The cometary origin, they say, also explains the rather unique shape 
> of the individual rocks in the cores and the striations that mark them 
> predominantly in line with their longest axis. (Apparently, these 
> markings are consistent with the process of erosion that must occur in 
> comet tails.)
>
> Zysman and Wallace also point out that the ice age that is associated 
> with esker and drumlin formation must have been caused by the comet 
> tail, which would have enveloped Earth in a layer of dust that rapidly 
> cooled the planet.
>
> This is not an entirely new idea. Various commentators have suggested 
> that many of Earth's rocks and much of its water and atmosphere may 
> have come from comets. And indeed this paper is an edited version of 
> one the authors originally gave in 1997.
>
> However, Zysman and Wallace's idea as it stands is little more than an 
> interesting guess. What of isotopic evidence? Presumably the isotopic 
> content of the rocky cores should differ in a measurable way from 
> material on Earth that has other origins. If this work has been done, 
> they make no mention of it.
>
> And the fact that we have not seen eskers and drumlins forming in the 
> two hundred years that we've been looking does not mean they did not 
> form in the past, during the many millennia that glaciers were 
> ravaging the Earth. (In fact, there are recent reports that scientists 
> have seen a drumlin forming for the first time in Antarctica.)
>
> And finally, it's hard to imagine that the debris from a comet tail 
> hitting the atmosphere at several tens of kilometres per second would 
> then land in a tear drop shape just a few tens of metres in size or 
> form a line a few tens of metres wide but hundreds of kilometres long.
>
> It should be straightforward to refute or dismiss this idea by 
> simulating of the kind of debris patterns that this kind of event 
> would produce. And in any case, the heat generated when rocks enter 
> the Earth's atmosphere melts their outer surface, giving them a 
> "fusion crust" that is easy to identify. Why don't the rocks in esker 
> and drumlin cores have fusion crusts?
>
> Putting Zysman and Wallace aside, however, it is still possible that 
> the Earth has been shaped by extraterrestrial forces in ways that we 
> are only beginning to grasp. For example, there is growing evidence 
> that the Solar System has been regularly disturbed by passing stars 
> and their accompanying discs of ice and dust. These events must have 
> had a dramatic impact on our world.
>
> It is becoming increasingly clear that conditions on Earth are a 
> product of the interplanetary and interstellar environment in ways we 
> are only beginning to understand. And of course we need new hypotheses 
> to explore this idea to its fullest extent.
>
> Ref: http://arxiv.org/abs/1004.0416 : Tails of a Recent Comet: The 
> Role Cometary Jets Play in Crustal Formation Esker/ Drumlin Swarms
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