What is Cenozoic Era? What are the periods of Cenozoic Era? Information about the rock types, fossils, earth surface.
Cenozoic Era; Towards the end of the Mesozoic Era the giant reptiles died out, possibly because they were unable to feed properly off the grasses and flowering plants that were then beginning to spread over the earth. The place of the reptiles was taken by the mammals, warm-blooded creatures feeding their young with milk. Mammals—whales and seals—began to live in the seas also. The ammonites and belemnites disappeared and were replaced by shellfısh.
The last great era thus included living things of kinds more familiar today and is called Cenozoic, meaning “recent life”. It is also known as the Age of Mammals. Originally the main part of this era was called Tertiary (from the Latin tertius, meaning “third”) and the last part was called Quaternary (from quartus, meaning “fourth”). The Quaternary Era is very short, but the term is still used because, being the latest era, so much is known about it and it includes the last great ice age and the appearance of man.
The Tertiary Era is divided into four periods, and each period takes its name from the commonest form of fossil found in its rocks. The periods are:
- 1. Eocene (the rocks contain fossils of plants and animals that were first beginning to look slightly like those of today).
- 2. Oligocene (fossils of plants and animals a little more like those of today).
- 3. Miocene (fossils of plants and animals yet more like those of today).
- 4. Pliocene (fossils of plants and animals very much more like those of today).
In Eocene times the North Sea came into existence. Sometimes it was bigger than it is today, covering much of southern and eastern England as well as northern France and Belgium. At other times it shrank to about its present size. Because of these changes in its size, the Eocene rocks of the London and Hampshire areas contain seashells at some levels and the remains of land plants at others. The climate must still have been hot for there were palm trees, turtles and crocodiles.
During the Oligocene Period the isle of Wight was built up by sediment from the land. At the same time there were great outbreaks of volcanic activity in northeastern Ireland and along the west coast of Scotland. Thus the chaik of these areas has big flat sheets of lava on top of it.
Towards the end of the Oligocene Period and in the Miocene Period, Europe’s last great mountain-building movements happened. The African continent pushed against Europe and Asia and the pressure forced certain parts of them to fold into mountain chains. The Pyrenees, the Alps and the Himalayas are the most famous of these. During the Miocene Period the British Isles were all dry land.
In Pliocene times East Anglia sank beneath the sea once more. However, the Rivers Rhine and Thames carried so much material into the sea from the land that a “bridge” was built up which joined England to Europe. Across this bridge herds of elephant, hippopotamuses and, very probably, primitive man wandered.
The Quaternary Era lasted only about 1,000,000 years and the main part of it is known as the Pleistocene (“most recent”) Period, which was followed by the Recent Period making up the present day and the preceding few thousand years.
Towards the end of the Pliocene Period the climate became much colder. Then in the Pleistocene Period it became very, very cold, and ice sheets spread southwards from the Scandinavian mountains.
When they were at their biggest, they covered the British Isles as far south as the Rivers Seveni and Thames, much of northern Germany and Russia, all Canada and the northern part of the United States. In the cliffs near Cromer and Lowestoft (England) rocks can be found that were carried by the ice from southern Norway. Several times the ice melted back and disappeared from the areas it had invaded, and feveral times it spread southwards again. It is possible that we are living between two of these very cold times and that in another 100,000 years the ice will come southwards again.