THE GEOLOGICAL TIME SCALE
Caste-de Buffon, the French scientist who first explained the geological history of the earth. The geological history of the earth helps us in decoding the evolutionary trend since the birth of the earth. On the contrary, the geological time scale helps us in understanding the evolutionary history of the earth that had occurred during a particular time period. The geological history of the earth is divided into Eras, the eras are further divided into Epochs and epochs are subdivided into Periods. The age of the earth is estimated to be 4.6 billion years but after radioactive dating, the age of the earth found to be 3.9 billion years. The age of the earth calculated on the basis of the radioactive elements is considered to be authentic.
THE GEOLOGICAL TIME SCALE
| ERA | EPOCH | PERIOD | AGE IN MILLION YEARS | EVENTS |
| AZOIC/PRE-PALEOZOIC | 1- ARCHEAN 2-CAMBRIAN/ALGONKIANS | 3787 | 1-NO FOSSILS. 2-GRANITE AND GNEISS ROCKS FORMED. 3-ARAVALI, DHARWAR ROCKS FORMED IN INDIA. | |
| PALAEOZOIC | PRIMARY | 1-PERMIAN 2-CARBONIFEROUS 3-DEVONIAN 4-SILURIAN 5-ORDOVICIAN 6- CAMBRIAN | 280 345 400 440 500 600 | 1- DURING PERMIAN PERIOD-AGE OF HERCENIAN OROGENY, NEW SPECIES OF PLANTS AND ANIMALS, POTASH RESERVES FORMED. 2-DURING CARBONIFEROUS PERIOD- REPTILES EMERGED ON LAND, AGE OF TALL TREES, COAL FORMED. 3-DURING-DEVONIAN PERIOD- THE FISH AGE, AMPHIBIAN ORIGINATED, FERNS GREW. 4- DURING SILURIAN PERIOD- THE AGE OF VERTEBRATES, LEAFLESS PLANTS ORIGINATED, CORALS ORIGINATED. 5- DURING ORDOVICIAN PERIOD- NO LIFE ON LAND, REPTILES FOSSIL FOUND. 6- DURING CAMBRIAN PERIOD- SEDIMENTARY ROCKS FORMED, WATER MOVED TO LAND, VINDHYAN RANGE FORMED IN INDIA, LIFE ORIGINATED ON THE EARTH. |
| MESOZOIC | SECONDARY | 1-CRETACEOUS 2-JURASSIC 3-TRIASSIC | 135 180 225 | 1-DURING CRETACEOUS PERIOD- DEVELOPMENT OF ANGIOSPERMS, GIANT TORTOISE EVOLVED, LIMESTONE FOUND IN THE SOIL, LAVA PLATEAU AND BLACK SOIL FORMED. 2-DURING JURASSIC PERIOD- THE AGE OF DINOSAURS, MOUNTAINS EVOLVED, FLOWERING PLANTS CAME INTO EXISTENCE. 3-DURING TRIASSIC PERIOD- THE AGE OF REPTILES, ARCHAEOPTERYX THE CONNECTING LINK BETWEEN REPTILES AND AVES FOUND. |
| CANINZOIC/CENOZOIC | TERTIARY | 1-PLIOCENE 2-MIOCENE 3-OLIGOCENE 4-EOCENE 5-PALEOCENE | 11 25 40 60 70 | 1-DURING PLIOCENE PERIOD- MORDEN MAMMAL EVOLVED, SHIVALIK FORMED, THE GREAT PLAINS OF NORTH INDIA FORMED. 2-DURING MIOCENE PERIOD-AQUATIC BIRDS DEVELOPED, LESSER HIMALAYAS FORMED, ELEPHANT DEVELOPED. 3-DURING OLIGOCENE PERIOD- APES ORIGINATED, ORIGIN OF GREATER HIMALAYAS. 4-DURING EOCENE PERIOD-PRIMATES EVOLVED, EARLY MONKEYS AND GIBBON EVOLVED. REPTILES DISAPPEARED. 5-DURING PALEOCENE PERIOD- APES EVOLVED MAMMALS DOMINATED. |
| NEOZOIC | QUATERNARY | 1-PLEISTOCENE 2-HOLOCENE/POST GLACIAL | 1 0.01 | 1-DURING PLEISTOCENE PERIOD-THE ICE AGE, FLYING BIRDS ORIGINATED, HUMANS AND OTHER MAMMALS DEVELOPED. 2-DURING HOLOCENE PERIOD-MAN STARTED AGRICULTURE AND DOMESTICATED ANIMALS |
