@jbskaggs said:
In your game my wife wanted to know if the volcano's erupt?
Yes :) But I don't have the animation yet. Here's how it works. A regular fire does 1 damage to all cities inside the radius. If any volcano is inside the radius as well, the fire is modified to "volcanic fire" and gains +1 damage. So placement can make a large difference in how dangerous your disasters are.
Each disaster type has a different environmental bonus modality that doubles or triples the damage. As another example, a regular hurricane turns into "tropical hurricane" if equator is inside the disaster circle, gaining +1 damage bonus, etc.