At the end of the Cretaceous, dinosaurs went suddenly extinct.
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history
白垩 (bái'è) literally means 'white chalk'; the period was named after the chalk deposits formed from microscopic plankton in the Cretaceous seas (cf. the White Cliffs of Dover). Latin Cretaceous is from creta = chalk, and Chinese mirrors that meaning exactly. The Cretaceous ended with the K–Pg extinction (the asteroid impact that wiped out non-avian dinosaurs).
memory
Other geological periods follow the same 纪 pattern: 三叠纪 (Triassic), 侏罗纪 (Jurassic, see 《侏罗纪公园》 Jurassic Park), 白垩纪 (Cretaceous), 第四纪 (Quaternary).
