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GEOLOGIC

TIME

The Earth is 4.55 billionyears old. Just like we break our year up into months, weeks, days, minutes and seconds, we break up geologic time into pieces so we can better understand it.

Eon: largest segment of geologic time; i.e. Archean, Proterozoic, Phanerozoic

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The Earth is 4.55 billionyears old. Just like we break our year up into months, weeks, days, minutes and seconds, we break up geologic time into pieces so we can better understand it.

Era: subdivision of an eon; i.e. Paleozoic, Mesozoic, Cenozoic

The Earth is 4.55 billionyears old. Just like we break our year up into months, weeks, days, minutes and seconds, we break up geologic time into pieces so we can better understand it.

Period: subdivision of an era; i.e. Quaternary, Tertiary

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The Earth is 4.55 billionyears old. Just like we break our year up into months, weeks, days, minutes and seconds, we break up geologic time into pieces so we can better understand it.

Epoch: subdivision of a period; i.e. Holocene, Pleistocene

The Earth is 4.55 billionyears old. Just like we break our year up into months, weeks, days, minutes and seconds, we break up geologic time into pieces so we can better understand it.

Each separate division of time is different from the others, by plant or animal life types that have evolved over time from single-celled organisms to complex

multi-cellular critters like you!

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Atmosphere, climate and continents have changed all throughout geologic time!

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Time in Billions of Years Ago

True Division of True Division of True Division of True Division of Geologic TimeGeologic TimeGeologic TimeGeologic Time

PRECAMBRIANPRECAMBRIANPRECAMBRIANPRECAMBRIAN

4550455045504550----570 mya570 mya570 mya570 mya

�Hadean

�Archean

�Proterozoic

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Precambrian

Famous for:

� Formation of Earth

�Oxygen atmosphere forms

� Single-celled, algae and wormlike organisms

� Remaining rocks are severely bent & folded,

so hard to read

� Several different glacial periods

THE EARTH FORMS 4.5 BYA

Volcanic outgassing releases carbon dioxide, water

& other gasses into the atmosphere, marking the

beginning of the Precambrian. There is little or no

oxygen in the early atmosphere.

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Slowly, over billions of years, the Earth cools and

rain falls to further cool & solidify the lava. Early

bacteria evolve, releasing oxygen into the air. This

allowed oxygen-breathing organisms to evolve.

Banded Iron Formation

Precambrian iron deposits show banding with iron

oxide (rust) due to increased oxygen in the

atmosphere & water.

What type of chemical

weathering is this?

OXIDATION

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PaleozoicPaleozoicPaleozoicPaleozoic

570570570570----245 mya245 mya245 mya245 mya

Cambrian

thru

Permian

Explanation of Adaptation & Evolution

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Paleozoic

Famous for:

� Beginning of abundant life

� Coal deposits

� Ends with major extinction & formation of

Pangaea

� Between the Paleozoic and the Mesozoic,

nearly 95% of all species on Earth died off.

� The cause or causes of this extinction include:

volcanism & climate change

Possible Causes of Permian

Extinction

� Extensive glaciation

� Lower sea level, so less aquatic

environment available

� Volcanic eruptions putting sulfur & ash

clouds into air, blocking sunlight

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Paleozoic

Climate:

�Ordovician: North America was on equator

& had warm inland seas

� Silurian: North America became very dry,

leaving huge salt deposits

� Carboniferous: lots of freshwater swamps

that left coal deposits in the east

� Permian: very dry climate and great ice age

Trilobites

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AGE OF FISHES

mesozoicmesozoicmesozoicmesozoic

245245245245----66.4 mya66.4 mya66.4 mya66.4 mya

�Triassic

�Jurassic

�Cretaceous

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Mesozoic

Famous for:

�Dinosaurs beginning in the Jurassic

� Ends with MAJOR extinction of over 50% of all organisms from meteorite impact

� Pangaea begins to break up

Climate:

�Mild climate, with very little glaciation

� Forests grew at the poles, and coral in Europe

DINOSAURS

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cenozoiccenozoiccenozoiccenozoic

66.4 mya 66.4 mya 66.4 mya 66.4 mya ---- nownownownow

Tertiary

&

Quaternary

periods

Cenozoic

Famous for:

� Age of Mammals

�Humans evolve

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CEnozoic

Climate:

� Tertiary: warm and humid, but temperatures

slowly decreasing until one quarter of the land

was covered in ice (the Great Ice Age) –

forests become grassland

� Quaternary: cycles of warming & cooling –

we’re now in a warm period (only 1/10th of

the area that used to be ice still is!)

Humans (Hominids)

Australopithecus

� Oldest hominid –5mya

� Apelike brains, humanlike jaw, bipedal

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Humans (Hominids)

Homo habilis

� 2mya

� larger brain, used simple tools

Humans (Hominids)

Homo sapiens

� 400,000y - today

� Larger brains

� Current humans are in this group

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DINOSAURSDINOSAURSDINOSAURSDINOSAURS and HUMANSHUMANSHUMANSHUMANSdid NOT NOT NOT NOT coexist!

Dinos died out 67 million years ago, while humans

have only been around 5 million years. Sorry, but

the Flintstones are a lie!

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Climate Change

Earth’s average temperature has increased

dramatically since the Industrial Revolution

started releasing more CO2 and other

greenhouse gases into our atmosphere. These

gases act as a blanket that trap heat and

increase global average temperatures.

Climate change

Seems to be relationship between CO2 & temperature

But, is the recent increase unusual?

Or common?

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Climate Change

Earth’s climate has changed repeatedly throughout

geologic time. The question, though, isn’t whether the

recent increase is unusual but if the recent increase is

going to hurt our current way of life. The answer to

that question is yes.

Climate Change:

effects

� Sea level rises, causing increased

flooding along coastlines

� More severe storms

� Droughts in certain areas

� Loss of plant & animal species

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