The Cretaceous is a geologic period that lasted from about 143.1 to 66 Ma. It is the third and final period of the Mesozoic Era, as well as the longest. At around 77.1 million years, it is the ninth and longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, 'chalk', which is abundant in deposits from the latter half of the period. It is usually abbreviated K, for its German translation Kreide.