We haven't seen a real volcanic event at least in 74,000 years - [Mount Toba] in Indonesia, in Sumatra, where the crater itself is 100 kilometers across. It was so monumental, what happened, that for a very long time the entire atmosphere of our planet was darkened. It's not the lava and the heat per se; it's the obscuring of the entire atmosphere, and it made it very difficult for the human race to survive.
Form is expressed in the light tones by dark accents, in the dark tones by light accents.