[meteorite-list] Tunguska -- Making An Impact At London 'Catastrophes' Conference

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:52:17 2004
Message-ID: <200208180419.VAA28024_at_zagami.jpl.nasa.gov>

Geological Society of London
London, U.K.

Contact:
Dr Iain Stewart
Department of Geography & Earth Sciences
Brunel University, Uxbridge UB8 3PH, UK
iain.stewart_at_brunel.ac.uk
+44 1895 203215

17 August 2002

Tunguska -- making an impact _at_ the London 'Catastrophes' conference

The "Tunguska Event" refers to the tremendous explosion on the
morning of June 30, 1908, that laid waste to about 2150 square
kilometres of Siberia in the region to the north and north-west
of Lake Baikal in Russia. The event is widely attributed to be the
impact of a comet or asteroid.

New research, however, is suggesting alternative homegrown
geophysical mechanisms to explain the event. Andrei Ol'khovatov,
an independent Russian researcher, will be convening a special
workshop to air the competing sides of the growing 'Tunguska
debate'.

For Ol'khovatov, the Tunguska event has all the hallmarks of an
extreme terrestrial geophysical event. He argues that it can
be explained by the combined effects of known tectonic and
meteorological activity -- albeit combined at a much larger
scale -- and argues that there is good evidence that such a
peculiar and rare combination of tectonic and meteorological
activity was reported from the Siberian region at the time of
the event.

Wolfgang Kundt of the Institute for Astrophysics at the
University of Bonn argues that the event was the result of the
tectonic expulsion of some 10 megatons of natural gas. This
natural gas, vented outwards at supersonic and subsonic speeds,
was responsible for the peculiar meteorological activity across
the region.

Another researcher, Christoph Brenneisen, reports that soil
samples collected by the second German-Russian Tunguska
expedition in autumn 2000 from the epicentre of the disaster
area showed clear enrichment of the disaster layer of 1908 with
alkaline earth metals such as lanthanides and strontium. However,
he argues that the source of these elements need not definitely
have an extra-terrestrial, but might instead come from the
Earth's mantle via deep-seated geologic-tectonic structures.

Jesus Martinez-Frias of the Centro de Astrobiología (CSIC-INTA)
in Madrid proposes an alternative impact origin for Tunguska,
that it may be related the fall of anomalously large atmospheric
ice blocks ('megacryometeors'). Such large ice blocks have been
reported striking the Earth's surface at an increasing rate
during the past few years. These unusual events of falls of
large blocks of ice were first reported in Spain in 2000, but
additional occurrences have been identified in many others
parts of the world (e.g. Italy, Austria, Argentina, Colombia,
Canada and The Netherlands). A research program was initiated
in Spain to study the nature of the ice blocks, showing that
they mostly share the characteristics of large atmospheric
hailstones. Professor Martinez-Frias argues that while
megacryometeors represent a much less violent threat than
extraterrestrial impacts, they constitute a more immediate hazard.

Notes for editor

This release is one in a series of media advisories for the
forthcoming conference Environmental Catastrophes & Recovery in
the Holocene (28 Aug - 2 Sept., 2002) Brunel University, West
London. For further information, contact the convener Dr Iain
Stewart. Please note that the Geological Society of London is
only promoting the conference, and is not able to take media
enquiries concerning it.

Abstracts

     http://atlas-conferences.com/cgi-bin/abstract/caiq-07
     http://atlas-conferences.com/cgi-bin/abstract/caji-24
Received on Sun 18 Aug 2002 12:19:49 AM PDT