Periodically Pralayas (destructions) take place. A destruction comes at the end of four thousand yugas on earth. For a hundred years there are no rains and there is widespread drought. Thereafter, Vishnu uses the rays of the sun to drink and dry up all the waters that there are on earth. Seven different suns appear in the sky and they burn up the three worlds of heaven, the earth and the underworld. The earth becomes as flat as the back of a turtle. The breath of the great snake (Shesha) also serves to burn up the three worlds.
After the three worlds have been burnt up, dark clouds full of thunder and lightning appear in the sky. For a hundred years it continue to rain. The rain puts out the fires that have been raging. From Vishnu’s breath are created tremendous winds and these drive away the clouds. But there is water everywhere. And Vishnu sleeps on these waters. For an entire kalpa he sleeps. The sages then pray to Vishnu for the three worlds to be created yet again.