Earth Science Chapter 23 Section 2 Mesozoic Era Earth Science Chapter 23 Section 2

Mesozoic Paleogeography Mass extinction of the Paleozoic Era provided opportunities for drastically different life forms The life forms filled empty niches Three Periods Triassic Jurassic Cretaceous

Breakup of Pangaea Beginning of Era Triassic Period Single global ocean Single continent Triassic Period Pangaea begins to break apart Heat beneath the continent caused it to expand Brittle lithosphere began to crack Cracks widened and continent began to split

Sea Ways Mid ocean rift systems developed Atlantic Ocean began forming Seaways widened Atlantic Ocean began forming Triassic Period

Changing Sea Level Mid-Ocean Rift systems partly responsible for rise in sea level Hot magma displaced seawater as new rock was formed Dropped, however, at the end of the Triassic Period Desert like conditions formed in Western North America Sea level rose again in Jurassic Period Continued to rise in Cretaceous Period

Mountain Building Collision of continents forced mountains upward

Cordillera An extensive chain of mountains Occurred in Western Laurentia Subduction of oceanic Farallon Plate beneath Laurentia’s western margin Rocky Mountains Sierra Nevada Mountains

Cordilleran Orogeny Phase One Occurred during late Jurassic and early Cretaceous Periods

Cordilleran Orogeny Phase One: Phase Two: Phase Three Steep Slow Subduction Phase Two: Shallow faster subduction Massive thrust faults Phase Three Very fast, very shallow subduction Tectonic activity inland Large vertical lifts

Mesozoic Life Phytoplankton Microscopic organism at the base of the marine food chain Abundant during Cretaceous

Mesozoic Life Plants As temperatures warmed, plant life changes. Tall cycad trees Seed plants with true flowers Ginkgoes Pine trees conifers

Mesozoic Life Terrestrial Animals Mammals Late Triassic Same time as dinosaurs Amniotic Eggs Contain food and water required by developing embryo

Mesozoic Life Dinosaurs Archosaurs Unique skeletal structure Speed and flexibility Hip structure allows legs to be held underneath the body (reptiles’ movement is more sprawling)

Mass Extinction Devastated terrestrial dinosaurs Today’s theory Most marine reptiles Plants Today’s theory Massive and volcanism and large meteorite (10 km diameter) impact caused climate problems Occurred at end of Cretaceous Caused long lasting greenhouse warming Layer of clay from that time contains high amounts of iridium Rare on Earth but common in asteroids