Originally Posted by ExpErdMann

Another explanation of the Tunguska event has been published, which may be better than the comet one (Wolfgang Kundt, Current Science, v. 81, n. 4, 399-407, 2001). Kundt argues that the event was caused by the volcanic ejection of "some 10 Mt of natural gas". He thinks the event was a modern-day formation of a kimberlite.

There is a lot of historical detail in the paper, and he uses this to support his argument. For example, one of the first scientists into the area was Leonid Kulik, who was also hoping to find meteoric nickel and iron. His team drained the 'Suslov' crater lake, only to find an intact tree stump at the bottom. This ruled out an impactor, since the stump should have been destroyed. There are other bits of evidence like this one. For example, he says the 'mystery clouds' seen after the explosion may have been rising blobs of natural gas.

Have seen something like this. Problem is that the energy release is too slow. A 'release' as stated would not produce a sonic shock, like that that was heard in London many k away.

He writes: "A kimberlite interpretation of the Tunguska catastrophe is tempting. ... kimberlite diatremes are narrow funnels, growing from a few metres across at a kilometre's depth to a dome-shaped tuff ring at the top, of diameter some kilometre, and occasionally enclosing a crater lake (reminiscent of the cauldron). ... An explosive injection from great depth is indicated, driven by volatiles".

The article is pretty interesting. There is a detailed map of the site at the time of the event, complete with the positions of various observers (and their fates!)