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Distribution of LAND areas and major OCEANS on EARTH

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By observing the fast and continuous expansion of theuniverse, modern astronomers have formulated the BIG BANGtheor .

By measuring the rate of expansion, they calculated that this event

must have taken place about 14 billion (14000 million) years ago.NOTE : Earths age is 4600 million years.

T i m e l i n e

4600 my9400 my

BIG BANG

FORMATION

14 000 million years

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As a result of this explosion, all matter must have been in a state ofPLASMA, consisting of a gas made of Hydrogen and Helium ions

Later, this PLASMA started to condense around centers to form

GALAXIES, consisting of billions of NEBULAs. At the same time, atomicfusion started to produce heavier atoms of new elements

WAY GALAXY

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Solar Nebula Theory is at present accepted for the formation of Earth

a) CONDENSATION into planetesimals

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b) Rotation of planetesimals about local centers

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c) Concentration into PLANETs, MOONs,ASTEROIDs and dust, by accretion of

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d) Formation of the SUN by fusion under Gravity

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e The SOLAR SYSTEM is formed 4.6 billionyears (4600 million years) before present (BP)

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Concentration Differentiation

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subcrust

Mantle (complex)

(solid)

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D zone

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osp ere s a con nuous s e ; s ro en n o a num erfragments. Each of these fragments are called a PLATE.

Each plate may be composed of either total SIMA (oceanic crust) ,or total SIAL (continental crust), or partly SIMA and partly SIAL.

Total SIMA (oceanic crust) and subcrust

Total SIAL (continental crust) and subcrust

Partly SIAL and partly SIMA with subcrust

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Major plates of the Lithosphere

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R

E

Continental Crust

Oceanic Crust v=6.5 km/sD: 2.7 v= 6.0 km/s

cean : . m

P

H

E

20 90 km thick : . m

H

O

S

u crus

D: 3.3 30 100 km thick v= 8.0 km/sL

IT

A S T H E N O S P H E R E (Low velocity zone)

D: 4.5 250 km thick v= 7.5 km/s

Note : Seismic velocities are given for P-waves, whereasS-wave velocities are about 2 km/s slower than P-waves.

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African PlateContinental Plate

SIAL

SIMABasaltic crust

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Major plates of the Lithosphere

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Heat circulation in the MANTLE roduces Convection Cells

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- vergen a es

SIAL (Silicium + Aluminum) SIMA (Silicium + Magnesium)

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2- Convergent Plates

Granitic crust

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subcrust

SIMA

Subduction Zone

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Transform boundaries mostly occur between two oceanic ridges..

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Ri t Ridge

Transform fault

Simple fault

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Transform boundary between two oceanic plates may also occure ween r ge an renc , or some mes e ween wo renc es.

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Collision of two Continents

Continental Plate

ASTHENOSPHERE

Melting

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European plate

Asian Plate

African PlateArabian

Plateplate

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TrenchConvergent plate boundary

TrenchConvergent plate boundary

Oceanic crustOceanic crust

AsthenosphereAsthenosphere

Subduction zoneUpwelling

Convection cell

Subduction zoneUpwelling

Convection cell