Birth of a Planet The history of Universe began

about 13.7 billion years ago with the Big Bang.

The Big Bang is a theory on how the universe formed.

Theory – an explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment.

Theories cannot be DIRECTLY TESTED; therefore theories can never be considered a fact.

This provided the elements to form the solar system

○ As material collected, high-velocity impacts of matter, called planetesimals, caused Earth’s temperature to increase

Birth of a Planet

Formation of Earth

Earth formed roughly 4.6 Billion Years Ago (BYA)

○ Iron and nickel melted and sank to form the metallic core while rocky material rose to form the mantle and Earth’s crust

Development of the Atmosphere and

Oceans During Precambian Time (4.6 Billion Years Ago

– 544 Million Years Ago), the Earth’s two atmospheres formed.

Earth’s First Atmosphere:

The Earth and its atmosphere was very hot.

The Earth was impacted by space debris such as meteors, comets, and asteroids.

The two gases that made up the first atmosphere were: Hydrogen (H) and Helium (He).

The Hydrogen and Helium eventually left the Earth’s atmosphere because they were so hot.

Hot gas molecules move very fast and drifted off into space.

Development of the Atmosphere and

Oceans

Earth’s Second Atmosphere Earth’s 2nd Atmosphere came primarily from Earth

itself.

There were lots of volcanoes, many more than today, because Earth’s crust was still forming. The volcanoes released ○ steam (H2O, with two hydrogen atoms and one oxygen

atom),

○ carbon dioxide (CO2, with one carbon atoms and two oxygen atoms),

○ ammonia (NH3, with one nitrogen atom and three hydrogen atoms).

Comets also added water (H2O), Carbon Dioxide, and Nitrogen (N). ○ Comet – a ball of dust and ice that orbits the sun.

Development of the Atmosphere

and Oceans Water vapor condensed to form clouds

and rainwater that formed the oceans

About 3.5 billion years ago in the oceans, photosynthesizing bacteria began to release oxygen

○ Oxygen levels steadily increased over time

○ Eventually oxygen levels were sufficient for ozone to develop in the atmosphere

Development of the Atmosphere and

Oceans

Geologic Time Scale o Divides geologic history into units.

o Originally created using relative dates.

o We will discuss how we accurately date in the next target

o Subdivisions o Eon

o Greatest expanse of time

o Four eons (Greek terms)

o Phanerozoic (542 Million Years Ago – Present) (“visible life”) – the most recent eon

o Proterozoic (“earlier life”) – such as bacteria

o Archean (“beginning”)

o Hadean – comes from the term Hades (Greek god of the Underworld) because Earth was fiery like the Underworld – the oldest eon.

Geologic Time Scale

o Subdivisions

o Era

o Subdivision of an eon

○ Eras of the Phanerozoic eon

• Cenozoic (“recent life”)

• Mesozoic (“middle life”)

• Paleozoic (“ancient life”)

• Eras are subdivided into periods

• Periods are subdivided into epochs

• WE WILL FOCUS ON ERAS AND

PERIODS of the PHANEROZOIC EON!!!

The Geologic Time Scale

Precambrian History

The Precambrian, which is composed of

the Hadean, Archean, Proterozoic eons,

spans almost 90% of Earth’s history

○ Much of Earth’s stable continental crust

was created during this time

Larger crustal areas were assembled into

larger blocks called cratons

Cratons form the core of modern continents

Formation of

continental crust

Precambrian History

Supercontinents

○ Large landmasses that consist of all, or nearly

all, existing continents

○ Pangaea was the most recent, Rodinia,

preceded it

○ Splitting and reassembling of supercontinents

have generated most of Earth’s major mountain

belts

○ Supercontinents have also profoundly affected

Earth’s climate over time

Possible configuration

of Rodinia

Phanerozoic Eon History

Phanerozoic eon encompasses 542

million years

○ Divided into the Paleozoic, Mesozoic,

and Cenozoic eras

Paleozoic era ○ Dominated by continental collisions as

Pangaea began to assemble

Formed the Caledonian, Appalachian, and Ural

Mountains

Formation of Pangaea

Phanerozoic History

Mesozoic era ○ Early in the Mesozoic, much of the land

was above sea level

○ By the middle Mesozoic, seas invaded

western North America

○ Pangaea began to break apart and the

westward-moving North American plate

began to override the Pacific plate

Phanerozoic History

Mesozoic era ○ Pangaea began to break apart and the

westward-moving North American plate

began to override the Pacific plate

Resulted in crustal deformation along the

entire western margin of North America

Formed the Sierra Nevada and Rocky

Mountains

Phanerozoic History

Cenozoic era ○ Much of North America was above sea

level throughout the Cenozoic

Eastern and western margins of the continent

experienced markedly contrasting events

Atlantic and Gulf coastal regions, removed

from active plate boundaries, were

tectonically stable

Phanerozoic History

Cenozoic era ○ Much of North America was above sea

level throughout the Cenozoic

In the West, the Rocky Mountains was ending,

the Basin and Range Province was forming,

and volcanic activity was extensive

Earth’s First Life

First known organisms were single-celled bacteria, prokaryotes, which lacked a nucleus

○ One group of prokaryotes, called cyanobacteria, used solar energy to synthesize organic compounds, thus producing their own food Fossil evidence of these bacteria include

layered mounds called stromatolites

The Paleozoic Era is divided into the following periods:

Cambrian (544 – 505 million years ago)

Ordovician (505 – 438 million years ago)

Silurian (438 – 360 million years ago)

Devonian (408 – 360 million years ago)

Carboniferous (360 - 320 million years ago)

○ Composed of two epochs: Mississippian and Pennsylvanian epochs)

Permian (286 – 245 million years ago)

Paleozoic Era: Life Explodes

Paleozoic Era: Life Explodes

Paleozoic marks the first appearance of life-forms with hard parts such as shells

○ Resulted in abundant Paleozoic fossils.

Cambrian Period - Life in the early Paleozoic was restricted to the seas and consisted of several INVERTEBRATE groups including

Trilobites

Cephalopods

Sponges

Corals

○ Invertebrates – animals without backbones.

Paleozoic Marine Invertebrates

Paleozoic Era: Life Explodes

During the Paleozoic, organisms diversified dramatically.

Silurian Period Insects and plants first appeared on land.

Devonian Period – Age of Fishes Fishes, such as sharks and fish with scales, dominate the seas

Lobe-finned fish adapted to land and became the first amphibians.

First land animals appear during the Devonian Period

Carboniferous Period Large tropical swamps in the Pennsylvanian epoch became the

major coal deposits of today.

The first true reptiles appeared.

Pennsylvanian-age coal swamp

Paleozoic Era: Life Explodes

During the Paleozoic, organisms diversified

dramatically

○ A mass extinction at the close of the Paleozoic

destroyed 70% of all vertebrate species on

land and 90% of all marine organisms

Scientists are not sure why the extinction

occurred but is evident from fossil layers.

Mesozoic Era: Age of the Reptiles

The Mesozoic Era is divided into the

following periods:

Triassic (245 – 208 million years ago)

Jurassic (208 – 144 million years ago)

Cretaceous (144 – 66 million years ago)

Mesozoic Era: Age of the Reptiles

Mesozoic, literally the era of middle life, is often

called the “Age of Reptiles”

Organisms that survived the extinction at the end

of the Paleozoic began to diversify

Fish, reptiles, and cone-bearing trees called

conifers survived (ex. Pine trees) Reptiles became the dominant land animals

First reptiles were small, but evolved rapidly, particularly the

dinosaurs

Triassic Period First dinosaurs appeared about 225 million years ago.

First mammals appeared ○ Mammals- warm-blooded vertebrate that feeds its young milk

○ The mammals were mouse-sized

Conifers (cone-bearing trees (ex. Pine trees)), palm-like trees, and ginkgo trees made up forests

Jurassic Period First birds such as Archaeopteryx and Pterodactyl appear

Dinosaurs became dominate although most were herbivores and the largest dinosaurs, such as Stegosaurus, existed

Cretaceous Period – Age of the T. Rex The T.Rex and other carnivorous dino theropods (some larger)

dominated the land.

The first flowering plants appears with fruits.

Mesozoic Era: Age of the Reptiles

Theropod Sizes

Archaeopteryx fossil

Figure 12.32

Mesozoic Era: Age of the Reptiles

At the close of the Mesozoic, another mass extinction occurred.

○ Many reptile groups became extinct

○ A few types survived, including the turtles, snakes, and lizards.

Most scientists believe an asteroid hit the Earth near the present-day Yucatan Peninsula in Mexico.

Other scientists believe climate change caused by a volcanic eruption or a parasite caused the mass extinction.

Cenozoic Era: Age of Mammals

The Cenozoic Era is divided into the

following periods:

Tertiary (66 – 1.8 million years ago)

Quaternary (1.8 million years ago – present

time)

Cenozoic Era: Age of Mammals

In the Cenozoic, mammals replaced the reptiles as the dominant vertebrate life-forms on land

○ One tendency was for some mammal groups to become very large

Tertiary Period

Whales and dolphins first evolved

The first grazing animals thrived as grasses began to cover the continents.

Cenozoic Era: Age of Mammals Quaternary Period

A series of Ice Ages occurred as the Earth’s climate cooled.

Many giant mammals, such as the woolly mammoth and sabored-tooth tiger died off after an ice age ended 10,000 years ago.

Today’s atmosphere is about 78% nitrogen, 21% oxygen, and 1% carbon dioxide and other gases.

The Cenozoic could also be called the “Age of Flowering Plants”

○ Flowering plants (angiosperms) strongly influenced the evolution of both birds and herbivorous mammals throughout the Cenozoic