Earth history is a fascinating subject. This 5-part series presents Earth's history in a chronological order with major events and eras explained. Links to the other parts are provided at the bottom of the article.

This text is taken out of my free online program MENTOR EARTH. It contains video material with images that explain all concepts even better. It is free (no hidden costs, no credit card required, no upselling). Read this blog article series or the course website if you want to learn more about it.

____________________________________________________________________________________

Notes

1. Abbreviations used in this text:

• • Ga = gigayears = a billion years

  • Ma = megayears = a million years

  • e.g. 4 Ga means four billions years ago from today.

2. This article explains the geologic time scale.

____________________________________________________________________________________

Part 1: Hadean to Proterozoic

 

Big Bang (13.8 Ga)

13.8 Ga

The Big Bang happens, and the universe starts to exist.

13.6 Ga

The Milky Way Galaxy is born.

4.567 Ga

Our solar system begins to form.

Hadean Eon (4.56-4.0 Ga)

4.566 Ga

The Earth starts to accrete, and the Hadean Eon begins.

4.53 Ga

30-60 Ma after the Earth starts to form, the core and mantle segregate to form Earth’s layers.

4.52 Ga

The Lunar Giant Impact happens. Earth, after differentiation of mantle + core took place, collides with a Mars-seized proto-planet oftentimes called Theia. As a result, the Moon forms.

About 4.5 Ga ago the accretion phase of Earth is completed.

4.4 Ga: Oldest dated terrestrial material + earliest oceans

The oldest dated terrestrial material is about 4.4 Ga old. It is a tiny zircon crystal that was found in a conglomerate, which is a sedimentary rock, in the Jack Hills in the Narryer Gneiss terrane in Western Australia. One of the zircons used to date the rock was 220 by 160 micrometers (μm) small. This is about three times the width of a human hair, using the average of about 75 μm. This tiny zircon tells us that continental crust has formed within 150-200 million years since Earth’s formation, and it also tells us that oceans were present at this time as well

4.1-3.8 Ga: Late Heavy Bombardment

The inner terrestrial planets and the Moon are battered by many asteroids, comets, and dwarf planets in an event called the Late Heavy Bombardment. The evidence of these impacts is visible on the scarred surface of the Moon that is covered with impact craters, and it is visible on Mars and Mercury as well. On Earth, no traces of the LHB have been discovered.

4.06 Ga: Oldest dated rocks

The oldest dated known rocks on the surface of the Earth, found in the Acasta Gneiss Complex in northern Canada, are 4.06 Ga old. It’s important to understand that a gneiss is a metamorphic rock. This means that a precursor rock was changed under high pressure and high temperature conditions without melting or without melting completely. The precursor rock of the Acasta Gneiss is thought to be 4.2 Ga old, so a little older.

Archean Eon (4.0-2.5 Ga)

3.49 Ga: Oldest undisputed evidence of life

The oldest undisputed evidence of life are 3.49-Ga-old stromatolites found near Marble Bay in the Pilbara region in Western Australia. Stromatolites are layered bodies that resemble rocks, but that were and are being built by photosynthetic cyanobacteria and other microbial life. Stromatolites dominate the Proterozoic Eon and still exist today, however not in equal abundance. Prominent examples live in Hamelin Pool, Shark Bay in Australia.The organisms that built stromatolites in the Archean were already complex. Certainly, it would have taken evolution some time to develop this complexity. Therefore, it is highly likely that life existed prior to 3.49 Ga ago. In fact, there exist other clues that could indicate relics of early life in 3.7-3.8-Ga-old rocks in west Greenland and in 3.7-4.2-Ga-old rocks in eastern Canada. However, these traces are carbon signals and iron-oxygen precipitates, respectively, that could have been left behind by life forms. No physical organism is visible, and it is very difficult to determine whether these signals are the remains of life or not. These findings are controversial, and it is highly debated whether these dubiofossils are the remains of early microbial life – whether they are the earliest fossils. 

Proterozoic Eon (2.5 Ga-539 Ma)

2.45 Ga: Great Oxidation Event (GOE)

This is groundbreaking. The GOE marks the first significant rise of atmospheric oxygen. Before that, oxygen was not present in the air. This new atmospheric oxygen is produced by single-celled microorganism called cyanobacteria that live in the oceans and that photosynthesize. They use sunlight, water, and CO2 to produce sugar and oxygen. However, the oxygen is a waste product and released as gas. This paves the way for animal evolution.

2.4-2.1 Ga: Snowball Earth

The entire surface or nearly the entire surface of Earth is covered with glaciers episodically. This ice age is called Huronian Glaciation. This cold phase is one of at least two extreme cooling events led to the so-called Snowball Earth during the Proterozoic Eon. This is the result of rising oxygen and sinking greenhouse gas levels, chiefly methane and CO2, in the atmosphere and, thus, the reduction of the greenhouse effect. All the while, Earth crust is continuously formed, and the continents grow into larger landmasses during the Proterozoic Eon. This is probably the peak time of continental crust formation.

1.8-1.5 Ga: Supercontinents Columbia and Rodinia

The supercontinent Columbia, also called Nuna, exists and the rocks at the very base of the Grand Canyon, that back then naturally didn’t exist yet, are deposited. These rocks today are 1.7-1.8-billion-year-old rocks and called Vishnu Basement Rocks. 

The supercontinent Columbia breaks apart into smaller continental pieces. In a new supercontinent cycle 1.3-1.1 Ga ago, these pieces collide again to form supercontinent Rodinia. Rodinia comprises the cores of the continents today and its true size and continental configuration are not known. Rodinia is stable until 750 Ma, when it breaks apart into smaller continent pieces and the Panthalassic Ocean opens.

720-635 Ma: Cryogenian Period 

During the Cryogenian Period the Earth was governed by very cold climate, leading to another extreme ice age. The entire globe froze over at least twice during this period and both cold phases lasted several tens of millions of years, resulting in another Snowball Earth event.

____________________________________________________________________________________

This was Part 1: Hadean to Proterozoic

You find the other parts here:

Part 2: Ediacaran to Silurian (comes soon)

Part 3: Devonian to Permian (comes soon)

Part 4: Triassic to Cretaceous (comes soon)

Part 5: Paleogene to Holocene (comes soon)

____________________________________________________________________________________

This 5-part series is about Earth’s history and the key events that happened since the formation of Earth using a chronological timeline. The knowledge about the past has the power to increase our gratitude and appreciation for what we currently have in our lives. These emotions go beyond the profound appreciation for the planet and permeate all areas of our lives. Pondering the future causes us to be aware that the world keeps on spinning after we’re gone. Then, there emerges a sense of responsibility to take care of the planet for future life. The simple awareness of the fact that Earth has a past and a future, that it existed before us and will exist long after our own individual death, causes a shift in our perception. Suddenly, we’re not owning the planet, but we inhabit it briefly. This awareness of time and our place on this planet can positively influence our behavior and attitude towards all forms of life, and turn us into thoughtful decision-makers, as our innate appreciation for nature is activated.

Yours,

Daniela

____________________________________________________________________________________

Sources

Images

Headline image: An artist illustration of a ‘snowball Earth’. Image credit: NASA.

Text

Please find all the sources listed in a spreadsheet that is available for download in my program MENTOR EARTH