Download NATURAL HISTORY OF EARTH I

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!
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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
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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
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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