These catastrophes are described in various Buddhist sutras. There are three greater calamities of fire, water and wind, which are said to destroy the world, and three lesser calamities of high grain prices or inflation (especially that caused by famine), warfare and pestilence, all of which threaten human society.
The seven disasters differ slightly according to the source, but they include war, foreign invasion and natural disasters. Nichiren (1222–82) combined these two different types of catastrophe in a single phrase to describe the disasters besetting Japan in his time.