The cataclysms come with geological upheavals volcanic eruptions, some parts of the Earth heating up to fiery temperatures, and in some cases fire storms from the sky. These fire storms are caused by reactions of atmospheric gasses to the Turmoil going on. Petrocarbons are in essence created, due to the flashes of lightning and intense heat due to passage over open volcanoes, and these petrocarbons rain down, afire, at times. With the atmosphere scattered, chemicals in the comet's tail similar to your petrol chemicals do not flash in a quick consummation into water and carbon dioxide, but descend close to the surface of the Earth before bursting into flame. A fire storm, killing all beneath it. All this has been reported in ancient times, as humans observed accompaniments to the cataclysms. This type of activity sets forests afire. Where vegetation regrows, from seeds and roots, many areas will nevertheless be denuded of vegetation for some time.
Note: below added during the Aug 31, 2002 Live ZetaTalk IRC Session.
We have stated that during the shift, that firestorms will results from air with petrochemicals components passing over super hot volcanic air. This binds the components, creating oil, which is the source of most of the oil buried underground on Earth. Mankind presumes that oil came from compressed and trapped vegetation, eons ago, but cannot duplicate this process. Why would vegetation result in oil, deep underground, when the process only results in methane and compost today? Petrochemicals are broken down by cracking, during the refinement process, and are thus sensitive to heat process. This is how they were created, in the first place! During the shift, so much is roiled about in the atmosphere, and so many volcanoes erupting, super hot air overhead, that binding occurs. This is evident in the recent [Papua New Guinea] oily substance found following a volcanic eruption, which man had no explanation for!