More about the Cretaceous Period

The Cretaceous Period is one of the three periods of the Mesozoic Era (a time in history when dinosaurs lived). It came after the Triassic and Jurassic Periods and was the last period of dinosaurs.

Triassic (250-201 mya)
Jurassic (201-145 mya)
Cretaceous (145-66 mya)

The name Cretaceous comes from the Latin word 'creta', meaning 'chalk'. This refers to the soft, fine-grained limestone that formed during this time in history. 

The famous White Cliffs of Dover in England are an example of these limestone deposits.

Pangaea on the move!

During the Jurassic Period, the giant supercontinent Pangaea had already split up into Laurasia and Gondwana. Laurasia broke up into North America and Eurasia and Gondwana into an eastern and western part.

It was during the Cretaceous Period that the continents really split completely. The western part of Gondwana split into South America and Africa. 

The rift between the two continents created a long chain of volcanic mountains underwater. As the ocean between South America and Africa got wider, the mountains grew and grew, displacing huge amounts of water. This made the sea levels around 100 metres higher than they are now.

The high sea levels of the Cretaceous Period covered some of the lands we know today. Half of Britain was underwater! 

By the end of the Cretaceous Period, most of the continents were how we know them today; except Australia (which was still connected to Antarctica) and India (which was floating about in the Indian Ocean).

The dinosaurs

The dominant animals on land were by far the dinosaurs. There were duck-billed dinosaurs like Shantungosaurus, three-horned dinosaurs like Triceratops and scariest of all, the Tyrannosaurus rex. The Spinosaurus and Iguanodon were other large reptiles.

The Pteranodon ruled the skies and the seas were filled with fish and sea creatures that fed the giant sea reptiles, ichthyosaurs and plesiosaurs.

The K-T extinction

At the end of the Cretaceous Period, something major happened. It was one of the most important events ever to occur in history, but it was another mystery! Scientists don’t really know what happened at all. 

A popular theory is that the Earth was hit by a giant meteor in the Gulf of Mexico off the Yucatan Peninsula. This would have caused many geological activities like volcanic eruptions which would have filled the clouds with smoke and dust, covering the Sun's light for years.

Around 70% of life in the sea died and all big land animals too, including almost all the dinosaurs.

The name for this massive extinction is the K-T event. The letter (K) stands for Cretaceous and the (T) for Tertiary, the time in history that followed the Cretaceous Period. 

What came next? 

After the dinosaurs were wiped out, it wasn’t long before mammals ruled the Earth. Modern birds, descendants of the dinosaurs, are all that remains of the dinosaurs that ruled the planet for so many millions of years.

Crocodiles were also able to survive because they were semi-aquatic.

Did you know?

• Coccolithophores are tiny floating algae with armoured coverings. These coverings are the main component of the chalk deposits that give the Cretaceous Period its name.
• The Cretaceous Period was the longest period of the Mesozoic Era.