Landscape during the Triassic period

Triassic period

The Triassic began after the worst mass extinction ever, at the end of the Permian. Life on Earth took a while to recover and diversify. The Triassic was characterised by heat, vast deserts and warm seas. Even the polar regions were warm, so lush forests grew there. However, the lack of other life, coupled with the period's particular environmental conditions, opened up some evolutionary opportunities. As a result, the very first mammals and dinosaurs evolved. During this time, the giant supercontinent of Pangaea began to break apart. The period ended as it had begun, with an extinction event that wiped out many species.

Began: Permian mass extinction
248 million years ago

Ended: Triassic-Jurassic mass extinction
205 million years ago

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What the Earth was like

A map of the Earth in the Triassic Period

Reconstruction of the Earth in the Triassic period, 248 million - 205 million years ago. Credit: Dr Ron Blakey, NAU Geology.

Desert Earth Desert Earth
A vast desert formed in Earth's prehistoric past when the supercontinent of Pangaea straddled the equator and stretched to the poles. Pangaea's position influenced ocean circulation patterns, and its huge size meant that there were vast areas where moist air from the oceans never penetrated.

Causes of extinctions

During this period the following events are thought to have contributed to the Triassic-Jurassic mass extinction.

Flood basalt eruptions Flood basalt eruptions
Flood basalt eruptions are a type of large-scale volcanic activity, both in terms of extent and duration, that can occur on land or on the ocean floor. A flood basalt may continue to erupt for tens of thousands - possibly millions - of years and the lava can cover hundreds of thousands of kilometres.
Climate change Climate change
Earth's climate is not constant. Over geological time, the Earth's dominant climate has gone from ice age to tropical heat and from steamy jungles to searing deserts.
Impact events Impact events
Impact events, proposed as causes of mass extinction, are when the planet is struck by a comet or meteor large enough to create a huge shockwave felt around the globe. Widespread dust and debris rain down, disrupting the climate and causing extinction on a global, rather than local, scale.

Types of fossils formed in this period

Trace fossils Trace fossils
It's not only the actual bodily remains of dead animals and plants that can become fossils. Things created or left behind by animals can also fossilise, such as their footprints, burrows and dung.

Life in the late Triassic

By Dr Jo Wright

At the dawn of the age of the dinosaurs, the world was very different. Dr Jo Wright, scientific advisor to the BBC One series Walking with Dinosaurs describes life in the late Triassic.

When dinosaurs first appeared about 230 million years ago the world was very different. There were very few of the animal groups we recognise today - no mammals, no birds and no lizards. But there were some lizard-like reptiles.

What? No grass?

The difference was also apparent in the plant kingdom. Plant life would have seemed very drab, just green and brown in colour. There were no flowering plants, so nothing like most of the common trees and shrubs today. What trees there were would have looked different, though some were relatives of modern day ferns and podocarps. There was no grass. Instead, low ground cover would have been ferns and mosses.

The Triassic world was unusual for another reason. About 20 million years before the appearance of the first dinosaurs, the biggest extinction the world had ever known had occurred. Over 90% of all plant and animal species then alive on land and in the sea had died out at this time. Even in the Late Triassic the world was still recovering, and there was not the usual variety of life normally found on earth.

It took more than 10 million years before ecosystems recovered and complex systems and larger animals took even longer. Most of the dominant land animals that were around when dinosaurs evolved were products of long and established lines of descent.

A giant desert

The continents of the triassic Earth were configured differently to today. All the land masses on the planet were joined together into one huge continent called Pangaea. This stretched from pole to pole and its central region was a vast inhospitable desert. We know this because the type of rocks that were deposited at this time have sedimentary features characteristic of a dry harsh climate.

As all the continents were connected, the animals and plants found in the fossil record from that time are very similar all over the world.

New life

The Late Triassic was an innovative time in the animal kingdom. By the end of the period not only the dinosaurs had appeared but also pterosaurs (flying reptiles), various kinds of marine reptiles, the first crocodiles and turtles, and the earliest true mammals.

Towards the end of the Triassic, 220 million years ago, there was another extinction, which wiped out many of the non-dinosaurs including the dicynodonts such as Placerias and primitive archosaurs such as Postosuchus. It was after this that dinosaurs really started to radiate and diversify.

Dinosaurs gain the edge

It was often assumed that the dinosaurs survived due to their superior speed and agility. We now think they were simply fortunate because they were not hit as hard by extinction. After the extinction at the very end of the Triassic, the dinosaurs were the only large land animals left.

BBC News about Triassic period