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Geologic eons & eras

prezi for dinosaur! course

Nancy Wilkinson

on 23 July 2017

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Transcript of Geologic eons & eras

1O o’clock is half a billion years, or 540 million years ago!
Beginning 540 million years ago, this eon is divided into three eras. The Paleozoic era is first,
when many plants, fish, amphibians, reptiles, and animals appeared. An extinction event ended the Paleozoic era at
11 o'clock.
When did dinosaurs live?
Eons, eras and periods
We start by imagining a clock showing billions of years instead of minutes, and imagining the earth was created at 12 o’clock.
4.6 billion years ago!
The earth is created...
Volcanoes covered the new earth for almost a billion years. Near the end of this time, at 2 o'clock, rocks and oceans
...2 o'clock is 3.8 billion years ago
Archean Eon...
During the next 1.3 billion years (from 2 o'clock to 5:30) the earth was three times hotter than now, with little oxygen. Bacteria began to grow in the oceans, changing sunlight into energy (photosynthesis) and
releasing oxygen
as waste.
...5:30 o'clock is 2.5 billion years ago
After the Hadean Eon comes the
After a billion years of busy bacteria, the earth’s atmosphere was oxygen-rich. Single cell and multi-cell life developed. The first simple animals (like sponges) begin to appear.
The Phanerozoic eon, (and the Paleozoic era)
is from 10 to 11.
11 o’clock would be 250 million years ago!
The Phanerozoic eon and the Mesozoic era is from 11 to 11:50.
The Mesozoic era is the second
in the Phanerozoic eon.
It is also called the
Age of Reptiles
because this is when
the dinosaurs lived!
50 minutes past 11 o’clock would be
65 million years ago!

The Phanerozoic eon (and the Cenozoic era) is from 11:50 to 12:00
The Cenozoic era is the last era in the Phanerozoic eon.
It is the era we live in today, and is also known as the Age of Mammals because the extinction of the dinosaurs allowed mammals to
rule the earth.
And almost 12 o’clock noon is where we are today - 12 hours (or 4.6 billion years) from
where we started!
Geologists tell time using rocks; dividing times into chunks called eons, eras and periods.
is the largest unit of time.
It is half a billion years or more.
is the next largest unit of time. Eons are divided into eras.
An era is several hundred million years long.
...and dinosaurs lived in different periods, within a specific era.
Let's go find them!
This is the
12 midnight
Dinosaurs ruled the land and sea. The Mesozoic era ended with an extinction event, and all the dinosaurs died.
Dinosaurs ruled the land and sea. The Mesozoic era ended with an extinction event, and all the dinosaurs died.
Eras are divided into
Proterozoic eon
From 5:30 to 10 o'clock
is the

Digya Kevin MacLeod (incompetech.com)
Licensed under Creative Commons:
By Attribution 3.0
Microsoft Clip Art
Hadean Eon
Full transcript