IMS 2 - Origin of Earth & Ocean

Solar System from dust cloud debris (solar nebula) 4.5 billion years ago due to big bang cosmic explosion 15 billion years ago – astrophysicists estimation

Solar nebula

-          Rotating, disk shaped mass

-          75 % H, 23% He

-          Revolve about the centre with gravity concentrated particles

-          Sun is formed

-          Outer disk region cooled & condensed, gas interact chemically & collide with other particles form planets

Protoearth

-          Bombarded by particles, heat energy trapped by new accumulated layer of material

-          Growing weight, compression, decomposition of radioactive elements (uranium/thorium) raise temp.

-          1^st few hundred million yrs, interior reach iron/nickel melting point, settle in centre of planet according to density (density stratified, organized & differentiated layered system)

-          Surface cool & solidify (thin crust)

-          Oceans & atmosphere forms

-          Parts: Solid inner core, Liquid outer core, Mantle, Upper mantle, Crust

Lithosphere

-          Thin rigid skin above mantle 1000°C

-          Continental crust 25-90km, avr. 35km, Si Na K Al Ca O Mg Fe (2.8 g/cm³)

-          Oceanic crust 5-10km, avr. 7km, Si Mg Fe O Ca (3.0g/cm³)

Asthenosphere

-          Weak, ductile, partially melted, hot, slowly flowing (4.5 g/cm³)

-          600km, Si Mg Fe O / Magnesium-iron silicates

Moho

-          Chemical boundary between crust & mantle (Andrija Mohorovicic discontinuity)

Lower mantle

-          Rigid dense to core (5.5 g/cm³)

-          1900km, Si Mg Fe O / Magnesium-iron silicates

Outer core

-          Liquid, 3200°C, 2200km, 10 g/cm³

-          Fe S

Inner core

-          Solid, 5500°C, 1300km, 12 g/cm³

-          Fe Ni