Earth Evolution

Earth Scientists piece together clues about the age and formation environment of rock sequences from different parts of the Earth's crust to create a single sequence of events spanning 4560 Ma of geological history, called the Geological Column.

Formation of our Solar System & Hadean Time (4560-3800Ma)

The exact timing of the Hadean/Archean boundary is still controversial due to the sparse rock record but is usually set at 3800 Ma. This time marks the end of the Hadean heavy meteorite bombardment, allowing the survival of the early Earth’s crust.

Studies of Archean rocks reveal that the early Earth was quite different from that of today. It had an inhospitable environment with superheated water, an oxygen-starved and poisonous atmosphere, intense volcanism, and was under constant bombardment by meteorites. Hot, steamy, barren and explosive, the Archean landscape was uninviting. Yet, it was here that life began.

Archean Geosphere
Geologists recognize that today’s continents are built around cores of extremely ancient cratons called “Precambrian Shields”. They comprise two types of rock association that developed mainly during Archean time: the low-grade granite-greenstone belts and the high-grade gneiss complexes, and are products of the differentiation of small proto-continents, which then collided to form larger landmasses.

Global distribution of Archean rocks in modern continents.
Known (red), suspected (pink). Areas with rocks or zircons older than 3.6 billion years are labelled by name.

The Proterozoic lasted about 2 billion years and accounts for 40% of the Earth's total geological history. The deep Archean oceans had become wide shallow seas with layers of marine sediments.

These Proterozoic carbonate platforms provided an ideal environment for primitive life forms such as anaerobic and aerobic prokaryotes to flourish and diversify. Fossils discovered within these carbonates record the evolution from simple single-celled organisms to first more advanced multicellular animals, some of which have relatives in modern times.

Continental masses, larger than those of Archean time accreted to become the first supercontinents. A major change in climate towards the end of the Proterozoic led to one of the most severe global ice ages on our planet.

The Early Paleozoic is divided into 3 periods:

Cambrian
542 - 488 million years ago

Ordovician
488 - 443 million years ago

Silurian
443 - 416 million years ago

"Paleozoic" literally translates as the "time of ancient life" and the Era started with a remarkable increase in the complexity of animal life.

During the beginning of the Early Paleozoic continents were flooded by shallow seas and life was entirely confined to the oceans. It was a profound period for life on Earth, when almost all major animal phyla appeared within an interval of as little as 10 million years. This sudden appearance of a spectacular diversity of life forms has been termed the "Cambrian Explosion of Life".

The Late Paleozoic is divided in three periods:

Devonian

416 - 359 million years ago

Carboniferous

359 - 299 million years ago

Permian

299 - 251 million years ago

The Mesozoic is divided in three periods:

Triassic
251 - 200 million years ago

Jurassic
200 - 146 million years ago

Cretaceous
146 - 65 million years ago

The Cenozoic is divided into two periods:

Paleogene
65 – 23 million years ago

Neogene
23 million years ago – present