3. earth_ts internal structure

8/10/2019 3. Earth_Ts Internal Structure

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Earths InternalStructure

CVE 3205

Engineering Geology

Wong Jee Khai


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Early Evolution of Earth

Begins about 14 billion years ago with the

Bing Bang, an incomprehensibly large

explosion that sent all matter of the

universe flying outward at incredible

speeds.

The debris (H2& He) began to cool and

condense into the first star and galaxies.


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Formation of the solar system according to

the nebular hypothesiswhich stated that

our solar system evolved from an

enormous rotating cloud called the solar

nebula.


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1. Dust and gases (nebula) started togravitationally collapse.

2. The nebula contracted into a rotating

disk that was heated by the conversionof gravitational energy into thermalenergy.

3. Cooling of the nebular cloud causedrocky and metallic material to condenseinto tiny particles.


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4. Repeated collisions caused the dust-size

particles to gradually coalesce into

asteroid-size bodies.

5. Within a few million years these bodies

accreted into the planets.


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As material accumulated to form earth, thehigh-velocity impact of nebular debris andthe decay of radioactive elements caused

the temperature of earth to steadilyincrease.

Iron and nickel began to melt producedliquid blobs of heavy metal that sanktoward the centre of earth. (Earths denseiron-rich core)


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Large quantities of gaseous materials

were allowed to escape from earths

interior, as happens today during volcanic

eruptions.


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Earths Internal Structure

When a meteorite impacts a planet or

moon, its energy of motion (called kinetic

energy) is transformed into heat energy.

As Earth grew larger and larger from

continual impacts, its temperature

increased.


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Radioactive decay of materials like

uranium, thorium and potassium also

added heat.

Because Earth became partly fluid, less-

dense molten materials (silicon, aluminum,

sodium, and potassium) were freed to

migrate toward the surface.


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Denser melted materials, such as molten

iron, sank toward the center of the

planet.

Planet Earth has three main parts:

1. Crust.

2. Mantle.

3. Core (metallic iron, nickel)


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Earths Crust

The crust is not uniform.

The oceanic cruston average is about 7

km thick and composed of the dark

igneous rock basalt.

The continental cruston average is about

35 to 40 km thick but may exceed 70 km in

mountainous regions and consists of many

rock types.


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Earths Mantle

Contains > 82% of earths volume.

Nearly 2900 km.

Can be divided into two different parts, thestiff lithosphereand the weaker

asthenosphere.


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Earths Mantle

The upper mantle extends from the crust-

mantle boundary down to 660 km depth.

Dominant rock type in the uppermost

mantle isperidotite, which is richer in

metals magnesium and iron.


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Earths Mantle

The lower mantle starts from 660 km

depth to the top of the core, at 2900 km

depth.

The rocks are very hot and capable of very

gradual flow.


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Earths Core

An iron-nickel alloy with minor amounts of

oxygen, silicon and sulfur.

Outer core is a liquid layer 2270 km thick.

Its the movement of metallic iron within

this zone that generates earths magnetic

field.

Inner core is a sphere having r = 1216 km

and is solid due to the immense pressure.


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Investigating Earths Interior

How do we know anything about the

composition of the core and the mantle?

By measuring the time required for

earthquake waves to travel through Earth

by different paths, we can determine the

composition of the materials through which

they move.


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3. earth_ts internal structure

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