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

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

3. 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

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

5. 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

6. Mountain Building
Collision of continents forced mountains upward

7. 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

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

9. 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

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

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

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

13. 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)

14. 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