earth’s past. the geologic time scale earth’s history is divided different sections of time the...

Earth’s Past

The Geologic Time ScaleEarth’s history is divided different sections

of time The sections are determined by the living

things and the rock recordThe geologic time scale is broken up into

eons, eras, periods, and sometimes epochs

Epochs – Divide

periods

Periods – Divide eras

Eras – Divide eons

Eons – Longest segment

of geologic time

ChangesEarth has changed dramatically over timeEarth atmosphere initially comprised of

CO2, Sulfur Dioxide, Water Vapor, and Nitrogen

Liquid Oceans DevelopedOxygen (O2) entered the atmosphere with

the appearance of photosynthetic organisms, such as algae

Living things have evolved and mass extinctions have occurred

EvolutionSince appearing on Earth, animals and plants

have been changing in appearance, size, and structure

This change is called evolution.In the 1800’s, Charles Darwin called the

process of the species that survive due to traits better suited to the environment natural selection

The Precambrian (4.5-543 mya)

Precambrian time includes all geologic time before the Cambrian period in the Paleozoic era.

This is the combination of the Hadean ArcheanProterozoic

The PrecambrianHadean●Archean●ProterozoicHadean Eon

The Formation of EarthMeteor ImpactsNo LifeVolcanic ActivityFormation of Early AtmosphereCooling of Water Vapor to Form Oceans

The PrecambrianHadean●Archean●ProterozoicArchean Eon (3.8-2.5 bya)

Started with the formation of the crust and first rocks (3.8 bya)

The Cratons are the oldest Archean

The PrecambrianHadean●Archean●ProterozoicThe first evidence of life

is found in Archean rocks Simple bacteria (3.8

bya)Cyanobacteria – simple

single celled organisms (3.5 bya) Trapped in sediment they

form structures called stromatolites

Photosynthesis began ~3 bya

The PrecambrianHadean●Archean●Proterozoic

Proterozoic Eon (2.5 bya -543 mya)

Abundant volcanic activity

No life on landAll organisms had

soft bodiesMulticellular life

began (2.1 bya)Taxa such as

jellyfish and worms appear at the end of the Proterozoic (1 bya)

Paleozoic Era (543-290 mya)

This era is the beginning of an abundant fossil record

It is broken up into six periodsCambrianOrdovicianSilurianDevonianCarboniferousPermian

PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●PermianCambrian Period (543-490mya)

The most commonly preserved Cambrian animal is the trilobite, a crablike invertebrate.

Very little mountain building Warm oceansAll life in waterCambrian ExplosionHard Shells evolved leaving a

better fossil record

PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian

Ordovician Period (490-443mya)The graptolite is a useful

index fossil of the Ordovician.

Appalachian Mountains formed as tectonic plates crashed into one another

All life in water


Silurian Period (443-417 mya)The eurypterid is sometimes

called a sea scorpion is a good index fossil .

Evolution of terrestrial (land)The first land animals

included distant relatives of spiders, millipedes, and scorpions.

The geologic time scale is broken up into…

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1. Centuries, scores, decades, years, and months

2. Eons, eras, periods, and sometimes epochs

3. Units4. Pounds and ounces

Which statement is true?

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1. An epoch is bigger than a period

2. An era is bigger than an eon

3. An epoch is bigger than an eon

4. An era is bigger than a period

What gave the earth the great majority of its oxygen in the atmosphere?

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1. Aliens2. Pollution3. Plants like algae4. Comets5. It was there in the

first place

What is evolution?

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1. Mass extinction of plants and/or animals

2. Plants/animals changing and adapting to better suit their environment

3. A time period4. An awesome band

name \m/

What is the oldest time period in Earth’s history?

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1. Proterozoic2. Archean3. Hadean4. Jurassic5. Cretaceous

When was the first evidence of life found?

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1. Proterozoic2. Archean3. Hadean4. Jurassic5. Cretaceous6. Silurian

When was the first evidence of life on land found?

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1. Proterozoic2. Archean3. Hadean4. Jurassic5. Cretaceous6. Silurian


Devonian Period (417-354 mya)“Age of the Fish”Lung fish first appeared

(ancestor to amphibians)First appearance of

forests consisting of ferns, giant rushes, and primitive conifers.


Carboniferous PeriodAKA: Mississippian and

Pennsylvanian PeriodsMississippian Period:Crinoids, which look

like plants, are actually invertebrate animals related to sea stars.

Foraminifera are one-celled organisms with tiny calcite shells.


Pennsylvanian PeriodFirst appearance of

reptiles, the first true land vertebrates (with backbone)

Large insects including early ancestors of the cockroach


Permian PeriodDry climateWidespread mountain building caused by continental

collisionsMass extinction ended the period and the Paleozoic EraMarine cephalopods and reptiles were among the survivors

Mesozoic Era (248-65 mya)The Mesozoic Era “Age of the Reptiles”

Triassic PeriodJurassic PeriodCretaceous Period

MesozoicTriassic●Jurassic●Cretaceous

Triassic Period (248-206 mya)Dinosaurs made their

first appearance on land.Some of the first

dinosaurs were about the size of a cat.

Cephalopods called ammonites are an important index fossil.

During most of the Triassic, almost all of Earth’s land was joined as the supercontinent Pangaea.


Jurassic PeriodMany larger

dinosaurs, including brachiosaurus and Allosaurus

Morphing insects like flies and caterpillars appeared

First birds appeared


Cretaceous PeriodThe largest dinosaurs

lived during this period, often exceeding 25 meters in length. (T-rex, Brachiosaurs)

The appearance of flowering plants is perhaps the greatest event.

Modern trees developed. Ex. oak, maple, birch.

MesozoicTriassic●Jurassic●CretaceousContinents appeared much

as they do today.Evidence supports asteroid

collision caused mass extinction at end of period

This ended the Mesozoic Era (183 million years of dinosaur domination)

Mammals survived the mass extinction

Cenozoic Era (65 mya -present)

Regarded as Earth’s recent history“The Age of the Mammals”Divided into three periods:

PaleogeneNeogeneQuaternary

CenozoicPaleogene●Neogene●Quaternary

Paleogene PeriodModern Mountain

Ranges:Rockies, the Alps, Himalayas,

Introduction of mammals

Global climate cooled

CenozoicPaleogene●Neogene●QuaternaryNeogene Period

Appearance of grasses lead to explosion of grazing animals such as sheep and cows

Modern forms of the horse, camel, and elephant debuted here

CenozoicPaleogene●Neogene●Quaternary

Quaternary PeriodGreat temperature fluctuations from

warm to cold, leading to increased rates of extinction and evolution

First appearance of humans

What period did crinoids appear?

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1. Cambrian2. Ordovician3. Silurian4. Devonian5. Carboniferous6. Permian

What period did reptiles first appear?

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What period did forests appear on land?

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What was the Mesozoic Era most known for?

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1. First appearance of life

2. First appearance of oxygen in the atmosphere

3. First appearance of land dinosaurs

4. First appearance of humans

Which period saw the largest dinosaurs?

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1. Cambrian2. Ordovician3. Silurian4. Triassic5. Jurassic6. Cretaceous7. Hadean8. Mississippian

What period did mammals first appear?

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1. Paleogene2. Neogene3. Quaternary4. Triassic5. Jurassic6. Cretaceous7. Hadean8. Mississippian

What period did humans first appear?

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1. Paleogene2. Neogene3. Quaternary4. Triassic5. Jurassic6. Cretaceous7. Hadean8. Mississippian

earth’s past. the geologic time scale earth’s history is divided different sections of time the...

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