Geological Time Periods

Okay so today I am going to give anyone who wants to read it the basic information about various Geological Periods throughtout time.Geologist and Palaeontologist divide the past into several different periods called eras, which are further subdivided into periods, each of which lasts for millions of years. The earth can be presumed to be around 4.5 billion years old dating back to the Precambrian era.

The Precambrian Era
The Precambrian Era is the longest geological era beginning 4.5 billion years ago and lasting approximately 4 billion years. The Precambrian era is generally separated into two eons the first of which being the Archaean Eon. spanning from around 4.5 billion years ago to 2.5 billion years ago, during this time air temperatures lowered and the water vapour condensed forming the first primeval oceans. This was a period of great volcanic activity when immense lava flows solidified both on the surface and below were transformed into rocks which were then carried by the first rivers to oceans where they were deposited at the bottom of the oceans forming the first sediments. The second eon was the Proterozoic Eon spanning from 2.5 billion years ago to 500 million years ago.

The Palaeozoic Era

Palaeozoic literally translates as ‘ancient life’; this era saw the occurrence of the oldest fish, reptiles and insects. During this era animals first began to have hard parts such as shells and carapaces in their bodies. The harder sections of the body fossilize well and it is from this era onwards that scientists have been able to successfully chart the rise and fall of individual groups of animals and plants. Beginning 500 million years ago and ending in an extinction event 248 million years ago. The Palaeozoic Era including:

• The Permian Period beginning 290 MYA (million years ago)
• The Carboniferous Period beginning 354 MYA
• The Silurian Period beginning 443 MYA
• The Ordovician Period beginning 490 MYA
• The Cambrian Period beginning 543 MYA

The Mesozoic Era
The Mesozoic era is commonly referred to as the ‘age of reptiles’ as during this time dinosaurs evolved into the dominate animal group on earth. Spanning from 248 million years ago to 65 million years ago the Mesozoic era saw the evolution of not only reptiles but also mammals and birds and ended in the extinction of the dinosaurs. This era consist of three periods listed below.

• The Cretaceous Period beginning 144 MYA
• The Jurassic Period beginning 206 MYA
• The Triassic Period beginning 248 MYA

The Cenozoic Era
A mass extinction event 65 million years ago marks the beginning of the Cenozoic Era or ‘recent’ era which is the current geological era. The extinction event at the end of the Cretaceous period destroyed everything larger then a crocodile including dinosaurs. The small animals that did survive found themselves in a very different setting as this era is also marked by the separation of the continents and the formation of their own unique plants and animals. The Cenozoic Era currently consists of two periods which are subdivided into seven epochs as depicted below.

The Quaternary Period consisting of the:

• The Holocene Epoch beginning 10,000 years ago
• The Pleistocene Epoch beginning 1.8 MYA

The Tertiary Period consiting of the:

• The Pliocene Epoch beginning 5 MYA
• The Miocene Epoch beginning 24 MYA
• The Oligocene Epoch beginning 34 MYA
• The Eocene Epoch beginning 55 MYA
• The Palaeocene Epoch beginning 65 MYA

The Holocene Epoch beginning 10,000 years ago is our current Epoch. Further information regarding these Geological time periods will eventually be posted on my website (when I have time). So thats all from me today, bye guys. If some of this is wrong blame the books I read not me.