AnearthquakeisashakingofthegroundcausedbythesuddenbreakingandshiftingoflargesectionsofEarth'srockyoutershell.Earthquakesareamongthemostpowerfuleventsonearth,andtheirresultscanbeterrifying.Asevereearthquakemayreleaseenergy10,000timesasgreatasthatofthefirstatomicbomb.Rockmovementsduringanearthquakecanmakeriverschangetheircourse.Earthquakescantriggerlandslidesthatcausegreatdamageandlossoflife.Largeearthquakesbeneaththeoceancancreateaseriesofhuge,destructivewavescalledtsunamis(pronouncedtsooNAHmeez)thatfloodcoastsformanymiles.
Earthquakesalmostneverkillpeopledirectly.Instead,manydeathsandinjuriesinearthquakesresultfromfallingobjectsandthecollapseofbuildings,bridges,andotherstructures.Fireresultingfrombrokengasorpowerlinesisanothermajordangerduringaquake.Spillsofhazardouschemicalsarealsoaconcernduringanearthquake.