1. catastrophe, cataclysm, geological phenomenon

usage: a sudden violent change in the earth's surface

2. calamity, catastrophe, disaster, tragedy, cataclysm, misfortune, bad luck

usage: an event resulting in great loss and misfortune; "the whole city was affected by the irremediable calamity"; "the earthquake was a disaster"

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See also: cataclysm (Dictionary)