The Precambrian Eon
The Precambrian Eon is very long - almost 4.5 billion years. For the first 3.9 billion years there were only simple cells. The Precambrian Eon ends when more complex animals evolved (worms, jellyfish, etc). This eon is special because it is divided into three more eons - the Hadean, Archean and Proterozoic! The Precambrian Eon is a supereon.
You may be wondering how life began on Earth? Scientists assume that cells formed accidently. However, it's also possible that they originated from a meteorite which crashed into one of Earth's oceans.
Jellyfish appeared close to the end of the The Precambrian Eon. They are now in every ocean.
The Hadean Eon
This eon occured 4,500 - 4,000 million years ago. This was when Earth was massive amounts of lava on it's surface and when asteriodes Kept smashing it. The air was full of dust and CO2. This was the time when the Moon formed - a small planet hit Earth and sent rock and dust flying into space. Earth's gravity caught it and it joined together to form the Moon.
This is a small amount of lava. In the Hadean Eon the Earth had giant patches of lava.
The Archean Eon
This eon occured 4,000 - 2,500 million years ago. In this eon the Earth's hard crust formed but was still being blown up by volcanoes. At this time it also rained for around 1.5 million years to form the oceans.
A wave in an ocean.
The Proteozoic Eon
This eon occured around 2,500 - 540 million years ago. In this eon the Earth colled down and ice and snow was present in some places. Furthermore, oxygen levels increased. Also, this is when simple animals like jellyfish appeared.
A jellyfish
Interesting Facts
We know all about Earth's past from fossils.
In the Hadean Eon there wasn't any oxygen.
Cells are so small that a human consits of around 75 trillion cells.
The Cambrian Period
The Cambrian Period happened 540 - 485 million years ago. The Cambrian Period is also part of the Paleozoic Era. The Phanerozoic Eon is divided into three eras. The eras are divided into many different blocks called periods. A period ends when a mass extinction happens or when different types of species appear. The Cambrian Period (in the Paleozoic Era) comes after the Precambrian Eon.
Fossils of a Trilobites - a Cambrian animal.
More about the Cambrian Period
Before the Cambrian Period, life was simple but in the Cambrian Period life was much more complex. There was never so much new animals in such a short time. Nobody knows how so many different animals appeared so shortly.
Ocean Creatures now.
Some animals from the Cambrian Period
- Anomalocaris
- Wiwaxia
- Marrella
- Opabinia
- Helicocystis
- Tamiscolaris
Interesting Facts
Most of the life in the Cambrian Period was in the ocean.
The Ordovician Period
The Ordovician Period is also part of the Paleozoic Era. This period had many invertebrates and corals and also had some land plants. Furthermore, this period ended with an ice age.
Corals
Mass Extinctions
The ordovocian was ended with a mass extinction - in this case an ice age. A mass extinction is when a large amount of species is wiped out in a short time (this can be a few million years). Mass extinctions include ice ages, a meteorite, etc.
Snowy mountains
The Ice Age Which Ended The Ordovonian Period
The huge ice age which ended the Ordovician is probably due to the first land plants. They "took in" lots of CO2 which made the Earth much colder.
Interesting Facts
The Ordovician Period got it's name from a Welsh tribe.
Life in the ocean suffered the most
The Silurian Period
In the Silurian Period the earliest animals on land appeared. Also, see levels rose. In addition, fish with bones appeared for the first time.
Modern fish
Interesting Facts
At that time there existed around 2 meter long scorpions!
The Devonian Period
The devonian period took place 420 - 300 million years ago. This period, often called the "Age of Fishes" was very important. Here, some creatures from the ocean went onto the land. Furthermore, there was a wide variety of rooted plants. Also, fish with gills, teeth and bones appeared.
Fish with gills.
What ended the Devonian Period
Scientists are not exactly sure what caused this mass extinction, but they have some ideas theories and they now that life in shallow waters suffered most. It's possible that an asteriod hit Earth. It's also possible there wasn't much oxygen by the seabed (that's where many animals lived).
Asterioid crater
Interesting Facts
75% of all species died due to the mass extinction!
There were massive coral reefs.
The Carboniferous Period
In the Carboniferous Period there were a lot of bogs and forests. Here, a lot of our coal was made when dead trees fell in swamps and other water.
Coal
What ended the Carboniferous Period
The climate got drier so therefore many trees died. In addition, there was a massive ice age which made things worse.
A dry climate
Interesting Facts
There were giant scorpions and thousands of insects.
The ocean was ruled by strange sharks
The Permian Period
The Permian Period is the last period of the Paleozoic era. It ended with a gigantic mass extinction which scientists think was a volcanic eruption that lasted for a million years!
A small volcanic eruption
What ended the Permian Period
The Permian period was finished with a giant volcaninc eruption. This was the biggest mass extinction ever. Lot's of gases and great amounts of dust were everywhere making the Earth more dark (the Sun couldn't shine).
Dust
Interesting Facts
There were many deserts
A massive amount of species were extinct
The Triassic Period
The Triassic Period is one of the three periods in the Mesozoic Era. This is when the first dinosaurs and mammals appeared.
A dinosaur fossil
What ended the Triassic Period
Huge volcanic eruptions ended the Triassic period. The eruptions let out lots of CO2 and other gases which caused sudden and very harsh global warming.
Pollution from factories
Interesting Facts
Grasshoppers were present in the Triassic Period.
The Jurrasic Period
The Jurrasic Period is best known for the dinosaurs. This is also when there were the first signs of birds.
A dinosaur fossil
Interesting Facts
This is when Pangea (all the continents together) started breaking apart.
The Cretaceous Period
The Cretaceous Period is the last period of the Mesozoic Era. This is when all dinasours got extinct
A dinosaur fossil
What ended the Cretaceous Period
A massive asteroid ended the Cretaceous Period but animals suffered more than plants.
A small asteroid
Interesting Facts
Every land animal with a weight over 25 kilograms died.
The Paleogene Period
The Paleogene Period is the first peroid of the Cenozoic Era. The Cenozoic Era is the era which we are living in. Here there are many birds and mammals.
A rhino
Some Animals From The Paleogene Period
- Horses
- Elephants
- Rhinoes
Interesting Facts
The Paleogene Period is sometimes referred to as the Age of Mammals.
The Neogene Period
This period started 23 million years ago. Many horses, apes and sheep appeared here.
A horse
Interesting Facts
The first humans appeared here six million years ago.
The Quaternary Period
This period is very special - this is when Homo sapiensappeared. We are Homo sapiens! This period started 2.6 million years ago and is still going on now. Minor ice ages also happened during this period.
Human bones model
Interesting Facts
In this period, around 10,000 years ago, most mammoths became extinct.