GEOLOGICAL HISTORY AND ITS DIVISIONS

As we know that in the ancient time, the subject matter of History and Geography was not separate.The credit of defining the scope of Geography and separating it from History goes to Emmanuel kant. He called History  as a chronical science and Geography as a chorological science. So when we talk abut Geological History, it is considered as major part of Geography because it is concerned with the evolution of the earth . 

GEOLOGICAL HISTORY -

Geological History of the earth is also known as the Geological clock, refers to the reconstruction of the various events which were part of evolution.Diagram of geological clock was given by f. Press and R. Siever in 1974

From the origin of earth to its present day form Geological History is divided into many sub periods on the basis of changes in life forms, tectonic activities, rock formations and mountain building processes. 

Geological History is divided into 4 majors eras(largest division of earth's history termed as eras) on the basis of rock deposition.such as Cenozoic, mesozoic, proterozoic, archezoic. Here is the description of different periods as represented by F. Press and R. Siever.

PRE-CAMBRIAN PERIOD 

1.Time period- 4.6 billion - 4.5 billion years ago.

 

2.The gaseous state of earth was changed into liquid state.Due to cooling and solidification of liquid matter, the solid outer crust. 

3. Formation of dense atmosphere around the earth due to the continued cooling and contraction of the earth. 

4 . Due to the condensation of water vapour, precipitation process began and rivers were formed. 

5. In plant kingdoms only marine plants originated or evolved for the first time. 

CAMBRIAN PERIOD

1.Time period -  4.5 billion  to 570 million years ago. 

2.Oceans were formed during this period around 3.8  billion years ago. 

3.Bacteria originated in oceans in about 3.5 billion years ago. 

4. Cambrian rocks of wales , north-west Scotland, Western England, Canada and U.S.A were formed during this period, volcanic activity in Europe started. 

5.Land life doesn't exist during this period but coral, jellyfish and worms lived in sea about 1.1 billion years ago and about 1000 species of vertebrates were evolved in this period . 

ORDOVICIAN PERIOD

1.Time period- 570 million to 500 million years ago. 

2.Due to the Deposition of mud and sand , many shallow became dry. 

3. Mountain building processes were started in this period. Ordovician rocks were formed in North West Europe and America. 

4. Climate was warm and Marine areas were affected by volcanic activity. 

5. Life was confined to sea only. Fossils and jawless fish appeared for the first time. Shell animal and some animals were common . 

SILURIAN PERIOD 

1. Time period -  500 million to 435 million years ago. 

2.During this period climate was warm but some areas  were characterised by dry climatic conditions . 

3. Volcanic activities were less in this period. 

4. Trilobites, Molluscus and coral were common . Small animals called Graptolites were found. 

5. Life originated for the first time on the land. Acc to some scholars, leaf less plants was the first living thing to be evolved on the land. 

DEVOCIAN PERIOD

1. Time period - 435 to 410 million years ago. 

 

2.During this period mountain building and volcanic activity were common and active. 

3. Most of the areas of North-west Europe and North America were characterized by warm and semi -arid climate. Remaining areas were dominated by uniform climate. 

4. Plants became part of evolution and green vegetations developed their leaves, branches, stems and roots. 

5. Species of Fish, Marine vertebrate, Amphibians were evolved in the end of this period. Spiders and Ants were the first mobile species to be originated on the land. 

CARBONIFEROUS PERIOD 

1.Time period - 410 to 330 million period 

2. This period is concerned with coal formation. 

3. Dry climate continued for long period but area having warm and wet climate developed large forests. 

4. First reptile appeared for the first time. 

5.This period is divided into 2 periods. 

A. LOWER CARBONIFEROUS PERIOD. 

1. Time period - 410 to 360 million years ago. 

 

2. The first forest grew in swamps. 

3. Water bodies contained many types of fish. 

4. Amphibians and insects appeared for the first time.

B. Upper Carboniferous period

1. Time period - 360 to 310 million years ago. 

2. Crustaceans, fish and amphibians were common. 

3. Coral reefs were formed and trilobites were dead in this period. 

  

WITH THIS PALEOZOIC ERA ENDS AND MESOZOIC ERA STARTS. 

PERMIAN PERIOD. 

1. Time period - 290 to 240 million years ago. 

2. Inland lakes were formed due to faulting. 

3. In Europe, high mountains were formed due to tectonic movements. 

4. Because of the climatic conditions, evergreen trees continued to decrease, dry and thorny forests were evolved. 

5. Cone bearing trees were common for the first time and reptiles were common. 

TRIASSIC PERIOD 

1. Time period - 240 to 205 million years ago. 

2. Warm and dry climatic conditions but became wet in the end. 

3. Marl and sandstones formed in warm seas. 

4. Mountains were covered with deserts and bushes . 

5. In this period cone bearing trees were common. Many fish evolved into their modern forms. Insects were common. Dinosaurs, first mammals and turtles appeared. 

JURASSIC PERIOD 

1. Time period - 205 to 138 million years ago. 

2. Land areas was dominated by forests and swamps and plains having lakes and rivers. This period is also concerned with reextension in marine areas. 

3.Deposition in lime in European region.

4. Cone bearing trees were common , Dinosaurs attained their largest size and mammals were small and primitive first birds appeared. . 

CRETACEOUS PERIOD 

1. Time period - 138 to 63 million years ago. 

2. In this period , coastal areas were converted into swamp lands. 

3. River flow became sluggish in this period , Delta and mountain formation. 

4. Flowering plants became common.Invertebrates and amphibians were also common . 

5. Dinosaurs died at the end of this period. 

WITH THIS MESOZOIC ERA ENDS AND CENOZOIC ERA STARTS. 

PALAEOCENE EPOCH 

1. Time period -  63 to 55 million years ago. 

2. Flowering plants were common. 

3. Invertebrates, fish, reptiles and mammals were also common. 

EOCENE EPOCH 

1. Time period  - 55  to 38 million years ago. 

2. The mountains formed during Cretaceous period uplifted and grew in size. The Indian and Atlantic oceans were extended due to sea floor spreading. 

3. Reptiles disappeared from the sea. Whales and sea cows were evolved. 

4. Primitive mammals and whales appeared. Grasses also appeared for the first time. 

OLIGOCENE EPOCH 

1. Time period - 38 to 24 million years ago. 

2. Intense earth movement were experienced in America and Europe. 

3. Processes related to the formation of Alps mountain were intiated. 

4. Climatic conditions became cold which led to the obliteration of forests in some areas but there was  expension of grassland therefore certain grass eating mammals were evolved. 

5. Primitive apes appeared in this period, huge rhino like animals disappeared. Camels, cats, dogs, horses and elephants developed. 

MIOCENE EPOCH

1. Time period - 24 to 5 million years ago. 

2. Oceanic area decreased while land area Increased. Mediterranean Sea surrounding by land. Alps mountains were formed and Himayalans mountains were uplifted during this period. 

3. Apes were originated in Asia and Africa . 

4. Flowering trees and plants attained their modern shape. 

PLIOCENE EPOCH

1. Time period - 5 to 2 million years ago. 

2. Many seas were formed due to the drifting of land area and modern sea life started. 

3.  Birds and mammals also became like today's form. 

4.Human like creatures appeared.

5. Shiwaliks were formed due to the tectonic activities. 

PLEISTOCENE EPOCH

1. Time period - 2 million to 1000 bc 

2. Ice Age began in this period and modern human beings developed. 

3. Large animals flourished which died towards the end of the epoch

4 . It is divided into 4 glacial and 4 interglacial periods. 

HOLOCENE EPOCH

1. Time period - 1000 before present

2. Technological advancement, Hunting and tamings of animals, development of agriculture, use of metals and other minerals. 

3.Modern animals gained their complete shape in this period.

4.Ice Age disappeared in this period.