Tunguska event of 1908 was to be of geophysical origin!

ANNOTATION

Here the author's idea (first it was published in IZVESTIA ACADEMY OF SCIENCES OF USSR in 1991, and now it is already rather popular among Tunguska researchers) is explained that the famous 1908 Tunguska event in Siberia was not an impact of a stony asteroid/meteorite or a comet, but a manifestation of geophysical (terrestrial) processes: roughly speaking, a result of coupling between tectonic and atmospheric processes in very rare combination of favourable geophysical factors.
In general it is based on the following:

Perusing Tunguska facts shows they don't conform with a stony meteorite or a comet fall.

Tunguska event in place and in time coincided with a strong upsurge of tectonic activity on regional and (partly) global levels.

There was strong and remarkable coincidence of Tunguska event with particular local and regional (and partly semi-global) meteorological conditions.

There were several other remarkable evidences of peculiarities in geophysical situation accompanied Tunguska.

Simultaneous realization of all these geophysical phenomena together with Tunguska as just pure accidental coincidence is very unlikely.
Remarkably, that on small scales similar geophysical micro-Tunguskas occur rather often.
The exact physical mechanism of Tunguska event is still disputable. In my opinion electromagnetic phenomena play large role in it.

You can read a text of my report at the Brunel University conference, London, 2002 on Tunguska and some other related stuff here, and, detailed factual info on the geophysical Tunguska is below.

Here is a note from SCIENCE magazine - a reaction on the above-mentioned discussion of Tunguska at the Brunel Univ. conference (SCIENCE's issue of Sept.13, 2002, p.1803):

MORE THEORIES ON TUNGUSKA

On the morning of 30 June, 1908, in the remote Tunguska forest of Siberia, a vast explosion charred and flattened trees across an area nearly as large as Rhode Island.
Scientists have been mystified for years over the cause, although prevailing wisdom has it that an extra-terrestrial chunk of ice or rock struck Tunguska (Science, 20 August 1999, p. 1205).
At a conference in London last week on environmental catastrophes, physicists from Russia and Germany rejected the 'ET hypothesis.' Andrei Ol'khovatov, formerly of the Soviet Radio Instrument Industry Research Institute, noted that decades of research has failed to find definitive traces of extraterrestrial material. No impact crater has been found and, more tellingly, patches of trees were left untouched near the epicenter of the blast.
Wolfgang Kundt, an astrophysicist from Bonn University, Germany, then proposed an alternative scenario: a massive gas explosion. A large natural gas deposit lies below the site, a well-known fact unconnected to the event until now, he said. Kundt has modeled a Tunguska 'outgassing' and says it would fit with eyewitness accounts of the event. "The geophysical hypothesis is a fresh idea," says Jesus Martinez-Frias of the National Aerospace Institute in Madrid, Spain "It could be the answer." But Ol'khovatov believes Tunguska was a "poorly understood strong coupling between subterranean and meteorological phenomena" that science is not yet ready to understand.