The dinosaurs and the mammals appeared during the Triassic period, roughly 225 million years ago. The dinosaurs went extinct 65 million years ago. The Mesozoic Era lasted about 180 million years, and is divided into three periods, the Triassic, the Jurassic, and the Cretaceous.
  • Epoch begins with earth devestated by asteroid impact;
  • North America and Eurasia connected off and on;
  • Africa, South America, Antarctica, Australia, and India
    (an island continent) continue to separate;
  • Pacific Ocean shrinks as Atlantic Ocean widens;
  • Climate warm and humid world-wide;
  • Ferns fill post-asteroid world until forests regrow;
  • Mammals, though still small “explode” into the land niches formely dominated by the dinosaurs;
  • Large, flightless birds become top predators;
  • Flowering plants (angiosperms) flourish & spread.
Name Diameter (km) Age (megayears) Dating method Morphological type Notes
Chicxulub, Yucatan, Mexico 150 66.043 ±0.011 40Ar/39Ar CONFIRMED Peak ring basin Cretaceous-Paleogene
Eagle Butte, Alberta 10 <65 Geological dating CONFIRMED Complex Shatter-coned Cretaceous rocks
Parry Peninsula, NWT 160 <65 K/T boundary timeframe IMPROBABLE Complex