THEORIES ON THE FORMATION NATURAL HISTORY OF EARTH OF EARTH I

COOLING OF EARTH ANCIENT ATMOSPHERE PRINCIPLE COMPONENT OF EARTH COMPONENTS OF EARTH ¥ Inner Core: (1261 Km), solid, rich in iron. Temperature up to 7,000oC, Metallic. ¥ Outer Core: (2270 Km) molten metallic layer rich in iron. ¥ Mantle: (2885 Km) rock layer capable of gradual flow. ¥ Crust: (5-40 Km) outer silicious skin.

ROCK EARTH’S CRUST CYCLES COMPOSITION OF EARTH’S CRUST GEOLOGICAL TIMES!

Element % O 46.6 ¥ Precambrian 4.6 B - 570 M years Si 27.7 ¥ Paleozoic (Ancient life) 570 M - 225 M years Al 8.13 ¥ Mesozoic (Middle life) 225 M - 65 M years Fe 5.00 Ca 3.63 ¥ Cenozoic (New life) 65 M - Present Na 2.83 K 2.59 Mg 2.09

Most other useful metals occur about 0.1 % Copper is present at less than 0.0045 %

GEOLOGICAL TIME SCALE IS DIVIDED INTO ERAS PRECAMBRIAN ERA (4.6 Billion - 570 Million years BP

¥ 3.5 B years: Oldest rock on earth ¥ 3.5 B years: Early bacteria and algea ¥ 2.5 B years: Build up of oxygen in atmosphere ¥ 1.3 B years: Formation of early supercontinent ¥ 0.570 B years: Break up of early supercontinent and the formation of multicelled organisms ANCIENT ATMOSPHERE Environmental factors have played a decisive role in the evolution of all life on earth. Thus, in order to study the evolution and development of cultural heritage of human beeings, it is necessary to have a brief understanding of natural history of EARTH

OLDEST LIFE ON EARTH BLUEGREEN ALGEA (Cyano bacteria) Stromatolites which date to 3.5 billion years are the earliest fossil evIdence for microbial life. Two important change took place during precambrian era: 1. Development of the biochemical apparatus of oxygen generating photosysnthesis 2. Emergence of a new kind of cell in which the genetic material is aggregated in the nucleus bounded by a membrane. STROMATOLITES PHOTOSYNTHESIS OF OXYGEN (Blue green algae)

OXYGEN CYCLE FORMATION OF FREE OXYGEN EVOLUTION OF ORGANISMS I EVOLUTION OF ORGANISMS II

GENESIS STANLEY MILLER’S EXPERIMENT PALEOZOIC ERA ERTH AT THE END OF PRECAMBRIAN 570 - 250 M years! ¥ 570 x 106 years: Early shelled organisms ¥ 480 x 106 years: Early fish ¥ 420 x 106 years: Early land plants ¥ 380 x 106 years: Early Trees, formation of coal deposits ¥ 300 x 106 years: Early reptiles ¥ 240 x 106 years: Final assembly of Pangaea

CAMBRIAN EXPLOSION PALAEOZOIC LIFE

Trilobites Ammonoids PERMIAN SEA LIFE Formation of Pangaea

THE CATASTORPIC END OF NATURAL CATASPROPIES AND PALAZOIC ERA LIFE ON EARTH ¥ 96% of all species became extinct ¥ Sea levels dropped considerably, exposing the shallow continental shelves. ¥ Super continent Pangaea proed to be unstable and began to drift into separate continental masses CHANGE IN NATURE BETWEEN Paleozoic & Mesozoic

EXTINCTION MASS EXTINCTIONS 1. Ordovicion (440 M years ago): 57 % of marine invertebrate genera. 2. Devonian (370 M years ago): :arge amounts of biomass died, tropic reefs vanished. 3. Permian-Triassic (250 M years ago): 96 % of marine invertabrates vanished. 4. Triassic (210 M years ago): Half of the genera of marine invertabrates vanished. 5. Cretaceous-Tertiary (65 M yearas ago): Impact of a astroid, end of the age of reptiles (dinosaurs) and beginning of the age of mammals. MESOZOIC ERA TRIASSIC SEA FLOOR 250 - 65 years !

¥ 240 x 106 years: Opening of Atlantic Ocean ¥ 180 x 106 years: Early birds and mammals ¥ 140 x 106 years: Early flowering plants ¥ 65 x 106 years: Extinction of Dinosaurs, formation of Alps

PLATE TECTONICS DURING MESOZOIC ERA

¥ Continents drifted to almost present ositions ¥ Atlantic and Indian Oceans opened at a pace of 2cm/year ¥ Africa swing around Gibraltar an d squeezed the Mediterranean ¥ India raced north from Antarctica slamming into Asia to form the Himalayas ¥ Australia moving north separated from Antractica PLATE TECTONICS

ERA OF THE REPTILES ¥ Mesozoic Era came to an end abruptly 65 M years ago togethe with the mass extinction of plants and animals ¥ The principal casualities among thte reptiles were the dinosaurs. ¥ L.W. Alvarez recognized 2 cm clay later at the Mesozoic (Cretaceous) and Canezoic (Tertiary) boundary enriched with iridium (30 times) at several places around the world. ¥ Iridium is poor in silicous Earth crust but found extensively in iron meteorites. ¥ It is now believed that an asteroid with 10 Km diameter had struct the Earth. This impact would eject debriss to space which would block sunlight for a lkong time (Possibly years)

END OF MESOZOIC ERA REAL REASON WHY DINOSAURS BECAME EXTINCT NATURAL CATASPROPIES AND MASS EXTINCTIONS LIFE ON EARTH