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Tunguska - making an impact @ the London `Catastrophes` conference

August 17, 2002

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 Astrobiolog'­a (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.

Geological Society of London, The