Geologic TimeBasics

Earth’s history is huge!In order to understand earth’s history, humans

must think in much larger units of time than those we use in our daily lives.

Millions & Billions of Years!

Therefore scientists broke all those events from all

those years into categories.

Earth’s history is huge!

•Measured in billions of years

Time

Eras

periods

epochs

•Measured in hundreds of millions of years

•Measured in tens of millions of years

•Measured in millions of years

Precambrian Time•Largest chunk of earth’s history

•Began 4.6 billion years ago•Ended 544 million years ago

1st MAJORMass Extinction

Towards the end of Precambrian Time (about 650 million years ago) massive climate change, “Snowball

Earth” Theory

As much as 70% of life forms went extinct.

There are 3 ERASin Geologic Time

The last 544 million years are broken into ERAS!

The First Era

Paleozoic Era (Pay-Lee-O-ZO-ic)

“Age of Fishes”

Paleozoic Era

Divided into 6 periods:CambrianOrdovicianSilurian

Mississippian Pennsylvanian

DevonianCarboniferousPermian

Carboniferous Period divided into 2 epochs:

2nd MAJORMass Extinction

At the end of the Paleozoic Era, Pangaea formed, massive climate

change.

As much as 95% of life in Earth’s oceans went extinct.

The worst extinction event in earth’s history

“Age

of Rep

tiles

”

Stegosaurus

T-Rex

The second Era Mesozoic Era

“Age

of Rep

tiles

”

(Mess-O-ZO-ic)

Mesozoic Era

Divided into 3 periods:

TriassicJurassic

Cretaceous

3rd MAJORMass Extinction

Mesozoic Era ends with another mass extinction due to climate change.

Scientists hypothesize that this extinction occurred because of an asteroid that struck

the Earth along with volcanic events.

85% of all species disappeared, making it the second largest mass extinction event in

earth’s history

Cenozoic Era“Age of Mammals”

The Third EraCurrent Era

(Sen-O-ZO-ic)

Cenozoic Era

Divided into 2 periods:

TertiaryQuaternary

Each of these periods is divided into several smaller epochs