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

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 7 Apr 2010 14:41:34 -0500
Message-ID: <F0AAF5B7A65A412292340EB1690271B1_at_ATARIENGINE2>

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
----------------------------------------------------------------
----- 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
> ______________________________________________
> Visit the Archives at
> http://www.meteoritecentral.com/mailing-list-archives.html
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
Received on Wed 07 Apr 2010 03:41:34 PM PDT