Jurassic Period

Age of conifers, Ginkgo, and sauropods

The Jurassic Period (201-145 Ma) is in the Mesozoic Era, occurring after the Triassic Period, and before the Cretaceous Period. The Jurassic Period is the middle Mesozoic Era.

Geologic Age

  • 201.3–145.0 Ma


Late Jurassic: 163.5–145.0 Ma

Middle Jurassic: 174.1–163.5 Ma

Early Jurassic: 201.3–174.1 Ma

Eon / Era/ Epoch

What happened during this time?




  • Domination of dinosaurs (saurischian)

  • First squids and birds

  • First frogs and salamanders


  • Warm tropical greenhouse conditions world-wide

    • Carbon dioxide level begin ~1,350 ppm, and increase to ~1,600 ppm before dropping to 1,330 ppm

    • Oxygen levels hover around 20-21%

  • The break-up of Pangaea; super-continent begins to rotate,

  • North America drifting westward, opening the Gulf of Mexico, forming the central Atlantic.

  • Mountain-building events are triggered that created the Rocky Mountains and the Sierra Nevada

  • Sea level rose and flooded large portions of the continents; shallow continental seas spilled out of the Tethys and Proto-Atlantic and spread across Europe,

  • Warm shallow seas were home to a rich diversity of life.

  • Much of central North America was flooded by wide sea way that at its height extended into central Utah called the Sundance Sea

Additional reading