The Mesozoic Era

The Mesozoic Era

Biblical Reference

He who forms the mountains, who creates the wind, and who reveals his thoughts to mankind, who turns dawn to darkness, and treads on the heights of the earth— the Lord God Almighty is his name..

Amos 4:13

The Mesozoic Era• The Mesozoic Era lasted from 251 MYA to

65 MYA. • Mass extinction of the Paleozoic Era

provided opportunities for drastically different life forms.– The life forms filled empty niches

• Three Periods– Triassic– Jurassic– Cretaceous

The Mesozoic Periods

Breakup of Pangaea• Beginning of Era

– 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

– Eventually Pangaea split into two separate landmasses - Gondwanaland and Laurasia

Seaways• The climate of the Mesozoic Era was

warmer than the Paleozoic Era.• With no glaciers, the oceans had more

water.• Mid ocean rift

systems developed – Seaways widened

• Atlantic Ocean began forming– Triassic Period

The Triassic World

The Jurassic World

The Cretaceous World

Changing Sea Level• Mid-Ocean Rift systems responsible for

rise in sea level– Hot magma displaced seawater as new rock

was formed• Sea Level dropped 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

Changing Sea Level• Sea level rose during most of the

Mesozoic Era.

Effects of Changing Sea Level• A beach environment covered the continents’

margins. Resulting sandstone covered by shale and

limestone deposits that included the first corals, building organic reefs.

Organic reefs are structures composed of carbonate skeletons made by living organisms.

Reefs affect the environments in which they grow.

Many new organisms evolved.

The Great Lakes area of North America contains huge deposits of Silurian-aged evaporite minerals, including halite, anhydrite, and gypsum that are mined commercially.

Mesozoic Geography• Throughout the Mesozoic era, the North

American continent moved westward.

• Its western edge collided with several small landmasses carried on an ancient oceanic plate.

• The Rocky Mountains began forming from this collision.

The Rocky Mountains

Mesozoic Life

Mesozoic Life

Mesozoic Life

Mesozoic Life• Phytoplankton

– Microscopic organism at the base of the marine food chain

– Abundant during Cretaceous– White Cliffs of Dover: Chalk deposits from

remains of shells

Life Moves to Land• For the first time in the history of life on Earth,

land was colonized during the Mesozoic.– Fossilized plant parts and spores suggest that

some form of land plant existed during the Late Ordovician.

Mesozoic Plant Life• As temperatures warmed, plant life changed

– Tall cycad trees– Seed plants with true flowers– Ginkgoes– Pine trees– Conifers

• Vascular plants have tissue for circulating water and nutrients through their stems and leaves.– The development of vascular tissue allowed plants to

spread out on land.

Mesozoic Plant Life• By the Late Devonian, three important groups

of vascular spore-bearing plants were living on land: ferns, sphenopsids, and lycopods.– During the Late Devonian, seed ferns developed. – The most important aspect of these plants was

the development of seeds, which allowed plants to spread out and colonize dry land.

Terrestrial Animals – Late Triassic• Mammals

– Same time as dinosaurs– Remained small during Mesozoic Era

• Amniotic Eggs

– Contain food and water required by developing embryo

Mesozoic Reptiles• Turtles• Crocodiles/Alligators• Lizards• Ichthyosaurs (large marine reptiles)• Pterosaurs (large flying reptiles)• Dinosaurs (land dinosaurs)

Two Groups of Dinosaurs• Ornithischian

– Hips were similar to modern bird hips– Carnivorous short-necked– Herbivorous, long-necked

• Saurischian– Hips were similar to reptile hips– Herbivorous with grinding-teeth– Herbivorous without grinding-teeth

Flying & Swimming Animals• Plesiosaurs: Mesozoic marine reptiles

with small heads, long necks, and flippers• Pterosaurs: Mesozoic flying reptiles with

large, batlike wings

Mass Extinction• Devastated terrestrial dinosaurs

– 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

Mass Extinctions

What organisms went extinct?• All dinosaurs• All pterosaurs• All ichthyosaurs• Many terrestrial plants• Many marine animals

What organisms survived?• Mammals

• Birds

• Trees with flowers • Many plants (ferns were the most

successful plant for a while)

• Small lizards/crocodiles/alligators/turtles

• Fish, squids, sharks, etc.

Australia’s First 4 Billion YearsAustralia’s First 4 Billion Years

A. the breakup of PangaeaB. Cretaceous extinction event C. formation of the Rocky

Mountains D. an ice age

What was the dominant geologic event of the Mesozoic era?

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A. the Cambrian came to an endB. dinosaurs slowly went extinctC. sea levels fellD. sea levels rose

What occurred during most of the Mesozoic Era?

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A. fishB. mammals C. plesiosaursD. pterosaurs

Which was a Mesozoic flying reptile with large, batlike wings?

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