The Shinmoedake volcano in Japan erupted and I don't understand the 'why's' of it but lighting storms are caused when these things happen - if memory serves me it happens with earthquakes too. Anyway we have enough basic science knowledge to understand volcanoes to some extent and lightning as well but can you imagine what a sight like this must have done to the psyche of onlookers a long time back? No wonder the end of the world, something unimaginable, can be imagined.
