Cataclasm is a disruption; breaking down: “This monsoon’s heavy showers resulted in a cataclasm of electrical and phone lines in several parts of the country.”
Cataclysm is a sudden and violent upheaval or disaster that causes great changes in society: “The revolution could result in a worldwide cataclysm.”
It can also refer to a terrible and devastating natural disaster; such as, a flood: “Palgues are cataclysmic events that can wipe out the entire population.”
