A rough history of planet Earth

Our planet is 93 million miles from the sun and was formed about 4,543,000,000 or 4.543 billion years ago. These are the very rough times that things happened in the past. Research is still going on, so new results might change some of these times in future. A billion years is 1,000,000,000 years.

Timeline of the history of life

Extinctions

Ice Ages

4.5 billion years ago: The earth is formed

At first the earth was hot and for many millions of years had lots of active volcanoes. It was bombarded with rocks from space as well. The atmosphere was mostly nitrogen and carbon dioxide with no oxygen at all. We wouldn't be able to breathe in this atmosphere because there was no oxygen. At first the earth was hot and for many millions of years had lots of active volcanoes. It was bombarded with rocks from space as well. The atmosphere was mostly nitrogen and carbon dioxide with no oxygen at all. We wouldn't be able to breathe in this atmosphere because there was no oxygen.

 

4.5 bn yrs ago: Hot earth

The surface temperature of the earth is about 200 Celsius. It is kept so hot by volcanoes, bombardment by meteors and radioactivity.

4.3 billion years ago: Water appears

Liquid water appeared on the earth’s surface. Before that the surface was too hot for water to be liquid. We think some of the water may have come from comets crashing into the earth. We know that a lot of comets are made mostly of ice.

   

3.8 billion years ago: Life begins

The very first forms of life of life were very small bacteria and similar things called archaea. They lived in water. They appeared about 700 million years after the earth first formed. The seas and oceans had been in existence for 500 million years and until now, nothing was living in them.

   

3.5 billion years ago: Single celled life begins

The seas were full of different kinds of single-celled life forms but no other life.

   

2.8 billion years ago: The atmosphere changes

Special bacteria called Cyanobacteria appeared and they used sunlight and carbon dioxide to produce sugars and oxygen. The oxygen they produced escaped into the atmosphere and changed it. Gradually the amount of oxygen in the atmosphere increased until it reached one fifth of the air (about 21%). The rest of the air is now mostly nitrogen. The atmosphere became quite like the one we breathe today.

 

2.4 to 2.1 billion years ago: Huronian Ice age

The earth became very cold and ice spread nearly everywhere. We think that the earth was like a giant snowball again.

3.8 billion years have gone by since earth was formed:

Nothing really important has changed for over a billion (one thousand million) years. Some scientists call these the “boring years”.

   

900 to 600 million years ago: Multicellular organisms appear

Animals, plants and fungi we know today have many cells. We call them multicellular. We humans are multicellular. The very first small multicellular life forms appeared around this time. We are not sure how it happened.

 

850 to 630 million years ago: Cryogenian Ice age

The earth became very cold again and ice spread nearly everywhere. The earth was again like a giant snowball.

540 million years ago: First animals with backbones appear

All this has happened in the seas and oceans. No animals are yet on land.

   

500 million years ago: the first animals come on to land

From fossils in Russia we now think that Dicksonia, which was flat, oval and about one metre or so long was possibly the first creature on land.

   

465 million years ago plants are on land too!!

The first plants appear on land but there are no flowers. At first there are mosses and lichens then later trees and ferns.

Ordovician: 444 m yrs ago

86% species lost

Devonian: 375 m yrs ago

75% species lost

Permian: 251 m yrs ago

96% species lost

Triassic: 200 m yrs ago

80% species lost

460 to 430 million years ago: Andean/Saharan Ice age

The extreme cold caused a major extinction. It was the second biggest extinction and this time many multicelled creatures died.

 

335 to 260 million years ago: Late Paleozoic Ice age

200 million years ago: Dinosaurs !

The early dinosaurs start to roam the earth. They remain for about 140 million years. Dinosaurs like Stegosaurus were alive from 160 million years ago to possibly 100 million years ago when they died out according to some scientists.

Tyrannosaurus Rex lived from 80 million to 66 million years ago. So the Stegosaurus had been extinct for at least 20 million years, some say 80 million years, before Tyrannosaurus Rex even lived.

   

140 million years ago: Flowering plants first appear

The very early dinosaurs probably never saw a flower because flowers hadn’t evolved yet.

   

65 million years ago: Dinosaurs become extinct

We think a large meteor crashed into earth and caused the extinction of many forms of life. But some small mammal like creatures and bird like dinosaurs survived.

Cretaceous: 66 m yrs ago

76% species lost

 

40 million years ago: Primates appear on land

Monkeys appear for the first time

   

25 million years ago: The first Apes

Apes evolved from monkeys

   

6 million years ago: Upright Apes

The first upright, ape-like creature appears which we think evolved from chimpanzees and bonobo monkeys. It walks on two legs not four.

Human beings!

We humans have been around for only the last 6 million years of Earth’s four thousand, five hundred million years of its existence. That’s not very long really. If you look at the history of animals on land, the Dinosaurs were roaming the earth for much longer: about 140 million years.

Flowering plants have only been on land for the last 140 million years of earth’s history which is is also fairly recent in the whole history of plant earth.

 

2.7 million years ago: Start of the recent (Quaternary) Ice ages

Believe it or not we are in an ice age.

Ice ages have times when there is a big increase in snow and ice called glacial periods. In between the earth warms up for a time and we call this an inter glacial period. During this ice age there have been several glacial and inter glacial periods.

12,000 years ago: Britain becomes an island

The island of Great Britain was still part of Europe. There was no water separating us from France. When the ice began to melt, the sea levels rose and the English Channel was created making Great Britain an island.

Some plants probably survived in Britain during the time of the ice and snow but as the climate warmed more plants started to grow. All the plants that arrived in Britain after the ice melted are called native plants.

After that many plants were brought to the country by humans. We call these introduced or alien plants.

 

12,000 years ago: The ice age ends

The last glacial period started about 110,000 years ago and ended 12,000 years ago. We are now in an inter glacial period. The ice and snow did not extend to the tropics and some countries like Australia had no glaciers at all.

During the various Ice ages there was an expansion of the cold areas with ice sheets sometimes forming. Only on a few occasions was most of the earth covered in ice though.

In Great Britain glaciers up to 1 km thick covered the north of the country and Wales while the south was very cold tundra.

Extinctions usually refer to the disappearance of multicelled creatures. We find that they suddenly stop appearing in fossils. Extinctions are never 100% though. The biggest extinction was the Permian when 96% of living things disappeared.

updated May 19th 2020, updated 20th May 2020, updated 21st May 2020, updated 1st June 2020