Era A unit of the geological time scale that is made up of several periods, e.g. the Mesozoic Era comprises the Triassic, Jurassic, and Cretaceous periods.
Era A unit of the geological time scale that is made up of several periods, e.g. the Mesozoic Era comprises the Triassic, Jurassic, and Cretaceous periods.
代：量度地质时期的分类单位，代由若干时期组成，如中生代包括三叠纪、侏罗纪和白垩纪。