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NATURAL HISTORY OF EARTH I COOLING OF EARTH THEORIES ON THE FORMATION 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 CYCLES EARTH’S CRUST COMPOSITION OF EARTH’S CRUST" Element % O 46.6 Si 27.7 Al 8.13 Fe 5.00 Ca 3.63 Na 2.83 K 2.59 Mg 2.09 GEOLOGICAL TIMES! • • • • Precambrian 4.6 B - 570 M years Paleozoic (Ancient life) 570 M - 225 M years Mesozoic (Middle life) 225 M - 65 M years Cenozoic (New life) 65 M - Present 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 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. BLUEGREEN ALGEA (Cyano bacteria) STROMATOLITES (Blue green algae) FORMATION OF FREE OXYGEN PHOTOSYNTHESIS OF OXYGEN OXYGEN CYCLE EVOLUTION OF ORGANISMS I GENESIS EVOLUTION OF ORGANISMS II STANLEY MILLER’S EXPERIMENT PALEOZOIC ERA • • • • • • ERTH AT THE END OF PRECAMBRIAN 570 - 250 M years! 570 x years: Early shelled organisms 6 480 x 10 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 106 CAMBRIAN EXPLOSION PALAEOZOIC LIFE Trilobites Ammonoids PERMIAN SEA LIFE THE CATASTORPIC END OF PALAZOIC ERA • 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 Formation of Pangaea NATURAL CATASPROPIES AND LIFE ON EARTH 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. TRIASSIC SEA FLOOR MESOZOIC ERA 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 MASS EXTINCTIONS NATURAL CATASPROPIES AND LIFE ON EARTH