Geological Eras

ByDr. Girish Chandra

Geological Time Chart

(By Dr Girish Chandra)

(Evolution of major groups of animals)

     Era

   Period

   Epoch

Million

Years

                       Organisms evolved

Coenozoic

Quaternary

Holocene   

       0.01-0

Dominance of man. Domestication of animals and agriculture. Modern genera and species evolved. Last ice age 30-40 thousand years ago. Woolly mammoth extinct.

Pleistocene      

1.5-0.1

Mass extinction. Huge floods. Ice age. Many large mammals extinct. Mastodons and woolly mammoth extinct. Prehistoric man evolved. Cave paintings.

Tertiary

Pliocene

6-1.5

Dry climate. Oceans shrink. Mammals increase specialization. Mountains rise. First hominids appear. First orchids.

Miocene

 23-6

Ice age. First man-like apes. Evolution of apes, monkeys, horse, elephant. Radiation of grazing mammals. Huge grasslands. All grass subfamilies distinct.

Oligocene

 37-23

Archaic mammals attain their maximum diversity. Creodonts (archaic carnivores) appear. First apes. Origin of grasslands.

Eocene

 53-37

Forests of monocotyledons and flowering plants appear. Ancestors of horse, camel, elephant appear. First bats.

Paleocene

 65-53

Climate warm. Vegetation abounds. Ancestors of most modern mammals appear.  Insectivores abundant. First grasses, Rhododendrons, whales and rodents.

Mesozoic

Cretaceous

 

 

135-65

Mass extinction. 60% of tetrapod families extinct. Himalayas, Andes, Alps arise. Dinosaurs and Ammonites extinct. First monocotyledons. First marsupials and placental mammals (Pantotheres). First flowering plants. Climate cool. Angiosperms radiate.

Jurassic

 

   205-135

First bird, Archaeopteryx. Dominance of dinosaurs. Earliest mammals. Dicotyledons and conifers common. Continents become high. Origin of insect pollinators.

Triassic

 

250-205

Mass extinction. 80% of tetrapod families extinct. Continental drift begins. Arid conditions. Gymnosperms dominate. First dinosaurs.Mammal-like reptiles. First teleosts, first crocodiles and first flying reptiles.

Palaeozoic

Permian

 

 290-250

Mass extinction. 70% of tetrapod families extinct. Single land mass, Pangaea and single ocean. Continents rise. Glaciations set in. Expansion of reptiles, origin of Cotylosauria and Therapsida. Last trilobites.

Carbonife-

rous

Pennsylva-

nian

290

Warm and humid climate. Swamps abundant. First modern soils. First reptiles. Sharks abundant. First mammal-like reptiles. Earthworms.

Mississipp

ian       

 

350

Forests of ferns and gymnosperms. Foraminiferans and shell-crushing sharks abound. First winged insects. Radiation of amphibians. Little seasonal variations.

Devonian

 

410-350

Mass extinction. Arid climate. First gymnosperm forests. First amphibians (Labyrinthodonts). First spiders. Dominance of fishes. First ferns. First vascular plants. First insects.

Silurian

 

440-410

Algae dominate. Land plants definite. Trilobites decline. First scorpions and millipedes appear. First fishes, ostracoderms and placoderms appear.

Ordovician

 

510-438

Land submerged. Warm climate. Algae abound. Plants invade land. First corals. First vertebrates. Cephalopods and snails. First Agnatha.

 

Cambrian

 

600-510

Mass extinction. Mild climate. Marine algae. Many invertebrates. Trilobites. Brachiopods. Sponges. Molluscs. Explosion after mass extinction.

Proterozoic

 

 

3,500-600

Primitive aquatic algae and fungi. Annelid burrows. Protozoa. Oxygenation of atmosphere. Prokaryote radiation. Skeleton of sponges.

Archeozoic

 

 

4,600-3,500

Calcareous deposits by algae. Origin of life. Fossils of cyanobacteria.

Solar

 

 

5,000-4,600

Formation of Solar system. Strong solar wind. Formation of primitive atmosphere on earth.

Cosmic

 

 

20,000-5,000

Big Bang and matter synthesis.

 

Geochronology, Dating, and Precambrian Time: The Beginning of the World As We Know It (The Geologic History of Earth)


Features: Rosen Education Service

Though it encompasses the majority of the Earths history, much about Precambrian time still remains unknown to us. With its climate extremes and unstable surfaces, Precambrian Earth hardly resembled the planet we see today. Yet for all its differences, it made the existence of future generations possible. This volume helps unlock the mysteries of prehistory by considering available geologic evidence while providing a deep dive into the finesses of geochronology.
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