The prophet will most likely be a very useful unit in the early epochs. As the game progresses, disasters will be less and less damaging to the opponent. To defend against a disaster you must build a temple per area. Volcano can also make buildings catch fire. Although this disaster is relatively stagnant, the area within its range will be devastated.
Earthquakes also shake the ground within a certain range.
Earthquakes are mainly good against buildings. Hurricane - Hurricanes form dark clouds, and destroy any ship that passes by. It might also cast lightning that ships can catch fire on. Hurricanes are best used against water units. Plague - Plagues are devastating to the population of the person that the plague is cast upon.