Bad Science on ancient meteorite impactor? - Part 2
Paul bristolia at yahoo.com Tue Apr 1 08:59:48 EDT 2008
In "Bad Science on ancient meteorite impactor?",
Sterling K. Webb wrote:
“See, I started out sceptical, and now I'm not so sure...
This collector considers "köfelsite" as an impactite:
http://www.somerikko.net/collection/index.html"Age between 8000 and 16000 years is from glass.
Theory has been recently presented that köfels has been
formed during a giant landslide about 9000 years ago.
That landslide was so huge that rock melted because
friction. So there is still a possibility that Köfels is not
an impact structure. However, there is lots of big
landslides in Alps but no other similar cases is found
yet. Also PDF's in quartz has been reported in samples
from Köfels, and PDF's are produced only by impacts."
http://www.somerikko.net/old/geo/imp/refer.htmThere has been iridium analysis, but it's inconclusive.”
The origin of the pumice, called either “hyalomylonites” or
“frictionites” associated with the Köfels has been studied in
great detail by:
Erismann, T. H., 1977, Der bimsstein von Köfels impaktit oder
friktionit?. Material und Technik. vol. 5, pp. 190–196.
and Erismann, T. H., H. Heuberger, and E. Preuss, 1977, Der
Bimsstein von Köfels (Tirol), ein Bergsturz-“Friktionit. Mineralogy
and Petrology. vol. 24, no. 1-2, pp. 67-119.
The abstract to Erismann et al. (1977) stated:
“For more than a century the genesis of the fused rocks
found in the landslide masses of Köfels (Ötztal, Tyrol)
has remained enigmatic. The initially promoted hypothesis
of a volcanic origin could not be backed by sufficient
evidence. So in the last decade the possibility of a meteorite
impact has been accepted by a large number of scientists.
It is, however, by no means in accordance with all facts
observed. In 1971, Preuss presented the idea of the melting
heat being generated by the friction between sliding and
stationary rock surfaces. As this working hypothesis
proved to be in good accordance with petrographic and
geomorphological evidence it was studied in detail by the
authors in cooperation with the Swiss Federal Laboratory
for Testing Materials (EMPA). The corresponding research
project (ldquoBig Sliderdquo) was based on a careful
analysis of the effects of the energy generated by the
landslide. By setting up plausible models for movement,
heat generation, and heat transfer and by solving the
resulting differential equations it became evident that —
as far as the landslide masses did not glide on a very
thick layer of stone powder (dynamically a rather
unprobable supposition)-large amounts of fused rock
(ldquofrictioniterdquo, for definition see chapter 2.2) must
have been produced. The enormous size of the particular
landslide was recognized as a determining factor in this
connection. The theoretical results thus obtained could
be backed experimentally by producting artificial pumice
under conditions approaching those of the Köfels landslide.”
Erismann et al. (1977) fairly well demonstrates that the estimated
kinetic energy of the rock mass displaced by the landslide would
have generated the heat necessary to melt the rock and form the
“pumice”, which they called “frictionite”. The frictionite occurs
in dikes several decimeters to meter thick at the top of the landslide
deposit.
The Köfels landslide, about 2 to 3 cubic kilometers in mass, is the
**largest** landslide in Europe. It is not surprising that it has some
unique aspects to it being the only one of its size in the region.
Another study, which examined glass found in the Köfels landslide is:
Masch, L., H.. R. Wenk, and E. Preuss, 1985. Electron microscopy
study of hyalomylonites-evidence for frictional melting in landslides.
Tectonophysics. vol. 115, pp. 131–160.
They studied glass, which they called “hyalomylonite”, which occurs
in the Köfels landslide deposits. It differs from frictionite in that it
occurs as veins 1 mm to 3 cm thick and lacks porosity. from their
analysis, they concluded that the hyalomylonite was created by
kinetic heating of the rock during the landslide.
Similar hyalomylonite / frictionite deposits has also been found in
megalandslides in the Himalayas of Nepal and Peru as discussed by:
Heuberger, H., L. Masch, E. Preuss, and A. Schrocker, 1984,
Quaternary Landslides and Rock Fusion in Central Nepal and in the
Tyrolean Alps. Mountain Research and Developments. vol. 4, no. 4,
pp. 345-362.
Weidinger, J. T., J.-M. Schramm, and R. Surenian, 1996, On preparatory
causal factors, initiating the prehistoric Tsergo Ri landslide (Langthang
Himal, Nepal). Tectonophysics. vol. 260, no. 1-3, pp. 95-107.
and
Legros, F., J.-M. Cantagrel, and B. Devouard, 2000, Pseudotachylyte
(Frictionite) at the Base of the Arequipa Volcanic Landslide Deposit
(Peru): Implications for Emplacement Mechanisms. The Journal of
Geology. vol. 108, no. 5, pp. 601–611.
Hermanns et al. (2006) presents significant problem for the impact
hypothesis in that he found that there is evidence of multiple landslides.
It was the largest and youngest of these landslides that created the
frictionite when it slid over the older deposits. To explain multiple
periods of landsliding, a person would have to argue that two different
impacts occurred at virtually same spot at different times separated by
a significant period of time.
Hermanns et al. (2006) also noted of the younger deposits, which
contain the frictionite:
“Pieces of wood recovered from a reconnaissance gallery
in the Tauferberg gave a conventional 14C age of 8710+/-150
years BP (Heuberger, 1966), and an AMS 14C age of 8705+/-
55 years BP (Ivy-Ochs et al., 1998),”
References Cited:
Hermanns, R.., L.. Blikra, M. Naumann, B. Nilsen, K. Panthi, D.
Stromeyer, O. Longva, 2006, Examples of multiple rock-slope collapses
from Köfels (Ötz valley, Austria) and western Norway. Engineering
Geology. vol. 83, no. 1-3, pp. 94-108.
-- Alledged PDFs --
Impacts and meteorites
http://www.somerikko.net/old/geo/imp/refer.htmThe above web page, states
“Also PDFs in quartz has been reported in samples
from Köfels, and PDFs are produced only by impacts.”
The alleged PDFs found in the deposits of the Köfels landslide were
examined by Dr. Christian Koeberl according to:
Deutsch, A., C. Koeberl, J.D. Blum, B.M. French, B.P. Glass,
R. Grieve, P. Horn, E.K. Jessberger, G. Kurat, W.U. Reimold,
J. Smit, D. stoffler, and S.R. Taylor, 1994, The impact-flood
connection: Does it exist? Terra Nova. vol. 6, pp. 644-650.
This paper reports that Dr. Koeberl found them **not** to be PDFs.
Rather, he identified them to be nonPDF llamellar deformation
features typical of tectonic, not impact, processes.
How these llamellar features formed is discussed by:
Leroux, H., and J.-C. Doukhan, 1993, Dynamic deformation of quartz
in the landslide of Koefels, Austria. European Journal of Mineralogy.
vol. 5, no. 5, pp. 893-902.
-- Additional Note --
Sorenson et al. (2003) concluded:
“Analysis of the Köfels sturzstrom seems to indicate
that most aspects can be explained without recourse to
exotic emplacement scenarios. The bulk of the material
resembles the debris from an energetic but conventional
landslide.”
Reference Cited
Sorensen, S.-A., and Berthold Bauer, 2003, On the dynamics of
the Köfels sturzstrom. Geomorphology, vol. 54, no. 1-2, pp. 11-19.
Yours,
Paul H.
