Cretaceous (Mesozoic 3)

Mesozoic Era 3: Cretaceous Period – Out with a Bang!

Key Events

  • Dinosaurs continue to dominate.
  • Flowering plants appear.
  • New groups of mammals and birds evolve.
  • The Cretaceous Period and Mesozoic Era end when an asteroid hits Earth at Chicxulub in Mexico.
  • A fast-moving cloud of dust, soot from wildfire and other ejecta material spreadsaround the globe in 4-5 hours. The Earth becomes dark and cold for about a decade, with longer-term changes lasting much longer (decades, or even hundreds of years).
Illustration of life during the Cretaceous Period.
Illustration of life during the Cretaceous Period. Copyright: Vix Southgate

Facts, Debates & Trivia

  • The Cretaceous Period is named after the Latin for chalk, creta.
  • Cretaceous rocks can be found in many places of the world.
  • The impact of a ~10 km diameter asteroid is thought to be responsible for the mass extinction, but volcanism may also play a part.
  • The Chicxulub crater is 200 km wide.
  • Other evidence for the impact includes a layer of the rare metal, Iridium, derived from vapourised material, that covers the entire globe.


  • The climate is warm.
  • High sea levels create numerous shallow inland seas.
The Earth 90 million years ago. The red dot marks the location of what will eventually become Cornwall. Credit: C.R. Scotese/I. Webster


201.3 – 145.0 million years ago 

(56.3 million years)

1 metre = 10 million years

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