when was the jurassic period

When Was The Jurassic Period & How Long Did It Last? Your Jurassic Period Questions Answered!

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When was the Jurassic Period? How long ago was the Jurassic Period? How long did the Jurassic Period last? On this page you’ll find the answers to all these questions and more…

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Introduction

pine cones
Conifers were the most common trees of the Jurassic Period.

There were no flowering plants in the Jurassic Period. Conifers (a modern variety of which is shown above) were the commonest trees of the period.

It was during the Jurassic period that dinosaurs became the dominant large land animals. These fearsome reptiles rose to power after a cataclysmic world extinction event, known as the Triassic-Jurassic extinction event.

The Triassic-Jurassic extinction event caused the dinosaurs' main competitors, the crocodile-like Pseudosuchians, to perish.

Let’s find out more about the Jurassic Period…

When Was The Jurassic Period?

The Jurassic Period began 201.3 million years ago (Mya) and ended 145 Mya. It was the second of the three periods of the Mesozoic Era.

When Were The Epochs of the Jurassic Period?

Just as hours divide into minutes, eras divide into periods. Unlike minutes and hours, however, geologic time periods (such as periods and eras) aren’t always the same length. This is because they correspond to layers of rocks in the Earth’s crust rather than set amounts of time.

The epochs of the Jurassic Period are shown below:

  • Early Jurassic: 201.3 – 174.1 Mya
  • Middle Jurassic: 174.1 – 163.5 Mya
  • Late Jurassic: 163.5 – 145 Mya

How Long Did The Jurassic Period Last?

The Jurassic Period lasted 56 million years.

What Came Before the Jurassic Period?

The period that came before the Jurassic Period was the Triassic Period (the first period of the Mesozoic Era).

What Came After the Jurassic Period?

The Cretaceous Period – the third and final period of the Mesozoic Era – followed the Jurassic Period.

Dinosaur Periods Diagram
Periods of the Mesozoic Era

Which Era is the Jurassic Period Part Of?

As we’ve found, the Jurassic Period is the second of three periods that make up the Mesozoic Era.

The first period of the Mesozoic Era was the Triassic Period. It began 251.9 million years ago (Mya) and ended 201.3 Mya.

The final period was the Cretaceous Period, which spanned from 145 Mya to 66 Mya.

Let’s Dig Deeper: The Geologic Time Scale

rock layers
Each period of the Geologic time scale corresponds to a layer of rock. New rock layers form over old rock layers. Therefore, the deeper down a fossil is found, the older it is.

The Jurassic Period is a period of time in the Geologic Time Scale. Like all periods in the Geologic time scale, it corresponds to the time in Earth’s history during which a certain layer of rock was being formed.

In the case of the Jurassic Period, that layer of rock is a layer of limestone in the Jura Mountains. The Jura Mountains are located on the France-Switzerland border. It is from this mountain range that the Jurassic Period gets its name.

There are three distinct bands in the main limestone layer. They correspond to the epochs of the Jurassic Period (the Early, Middle and Late Jurassic Epochs).

The limestone layer was first observed by the Prussian scientist Alexander von Humboldt in the late 18th century. He realized that the rocks corresponded to an unnamed chapter in Earth’s development.

Fossils in Jurassic Rock

Allosaurus skeleton
The fossilised bones of animals such as this Allosaurus appear in Jurassic rocks. Photo by Kabacchi [CC BY 2.0]
Because new rock layers form over older rock layers, the further down you dig, the older the rock becomes. Any fossils you find in the upper layers are likely to be newer than those found in deeper layers.

The fossils found in the Jurassic rock layer represent animals that were alive during the Jurassic Period. By studying the fossils present in Jurassic rocks, paleontologists can build up a picture of life in the Jurassic Period.

Global Extinction Events Before the Jurassic Period

volcano erupting
Volcanic eruptions may have caused the Triassic-Jurassic extinction event.

The entire Mesozoic Era began after the worst extinction event the world has ever experienced. During this time around 90% of all species on Earth became extinct.

During the course of the Triassic Period life once again began to flourish. Reptiles in particular benefitted from the new conditions. Because of this the Mesozoic Era is now known as the ‘Age of Reptiles’.

Between the Triassic Period and the Jurassic Period there was another extinction event.

Although not as severe as the previous extinction event, the Triassic–Jurassic extinction event saw between 70 and 75% of all species become extinct.

At the end of the Triassic Period the dominant land animals were a group of reptiles called Pseudosuchians. The Triassic–Jurassic extinction event saw most pseudosuchians become extinct.

This allowed another group of reptiles to take their place: the dinosaurs!

Thanks to the intense interest in dinosaurs, the Jurassic Period is one of the best-known of all periods of Earth’s history!

Dinosaur Information on Active Wild

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