cataclysm cataclysm /ˈkætəˌklɪsəm/

noun

1. An event resulting in great loss and misfortune  ( cataclysm , calamity , catastrophe , disaster , tragedy )
   an event resulting in great loss and misfortune
    The whole city was affected by the irremediable calamity
   the whole city was affected by the irremediable calamity
    The earthquake was a disaster
   the earthquake was a disaster
   
   
2. A sudden violent change in the earth's surface  ( cataclysm , catastrophe )
   a sudden violent change in the earth's surface