回到第一頁 Plate Tectonics Theory 回到第一頁 Objectives n to explain the distribution and formation of fold mountain, volcanoes and earthquakes.

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Plate Tectonics Theory

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Objectives to explain the distribution and

formation of fold mountain,

volcanoes and earthquakes

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Earth crust is made up of 7 major plates and many smaller plates

1.African plate 2.Eurasian plate 3.Pacific plate

4.North American plate 5.South American plate

6.Nazca plate 7.Antarctic plate

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Earth crust is made up of 7 major plates and many smaller plates

1.African plate 2.Eurasian plate 3.Pacific plate

4.North American plate 5.South American plate

6.Nazca plate 7.Antarctic plate

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Types of plate

1.Continential plates

consist of both continential crust and oceanic crust

2.Oceanic plates

consist of oceanic crust

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Motion of plates

plates are in constant movement

driven by large-scale thermal conv

ective currents within the mantle

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Diagram showing the convective currents and plate movements

MantleConvection currentsPlate movements

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3 types of plate boundaries

1.Constructive plate boundary

2.Destructive plate boundary

3.Conservative plate boundary

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Constructive plate boundary plates are moving apart

sea-floor spreading

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What happens...when oceanic plates pull apart?

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When oceanic plates pull apart, magma rises up.

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magma rises up from the mantle forms long submarine ridges

known as Mid-Oceanic Ridge

New Ocean Floor

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Formation of Mid-Oceanic Ridge

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Some magma breaks through the oceanic plates and forms submarine volcanoes.

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Some of these rise above the ocean surface and form volcanic islands.

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Destructive Plate Boundaries plates are moving towards each

other 2 conditions:

2 continental plates approach each other and collide

when an oceanic plate and a continental plate move towards each other and collide

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When 2 continental plates collide

sedimentary layers between them are compressed and folded

fold mountains are formed e.g. Alps and Himalayas fissures are developed due to

intense folding magma intrusion forms volcanoes earthquakes

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Formation of

Fold Mountain when 2 continental plates collide

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(a) collision of two continental plates

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(b) sea floor covered with sediment

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(c) sedimentary layers crumpled into fold mountains

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When an oceanic plate and a continental plate collide

the denser oceanic plate is drawn under the edge of the continental plate

the oceanic plates are melted in the hot mantle

this process is known as subduction a trench is formed along the zone of

subduction eg. Marianas Trench

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Sediments brought by erosive agents deposit on the trench forming layers of sediment

as the plates continue to approach each other, the sedimentary layer will be crushed and crumple to form fold mountains

e.g. Andes and Rockies

When an oceanic plate and a continental plate collide...

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Formation ofFold Mountain when one oceanic plate and one continental plate converge

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(a) collision of oceanic plate and continental plate

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(b) sediments crumple as plates squeeze together

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(c) sedimentary rocks are squeezed to form fold mountains

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Conservative Plate Boundary plates slide past each other neither construction nor destruction

of plates occur it usually produces earthquakes e.g. San Andreas Fault in

California (U.S.A)

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Diagrams ofConservative Plate Boundary

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A diagram showing the conservative plate boundary

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Example of Conservative plate boundary :

The San Andreas Fault in California and plate movements there

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Photograph of part of the fault

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A Summary of Plate Tectonic Theory

Constructive

Boundaries

Destructive

Boundaries

Conservative

Boundaries

Plate movement divergence convergence sliding

Force tensional forces compressional

forces

shear forces

Process sea-floor spreading subduction faulting

Associated

tectonic features

1. mid-oceanic

ridges

2. volcanic islands

1. trenches

2. fold mountains

3. volcanoes

4. volcanic island

arc

earthquakes

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Diploma in Education (Part-Time) 1997

Course Title: Educational Communication and Technology

教育傳意與科技Course code: EDD5161R - Group 1

Instructor: LEE Fong-Lok 李芳樂 Title: Plate Tectonics Theory

Student: CHIU YUK WAH 趙煜華 (97099240)

LEE YING YEE 李英怡 (97023330)

LIU MAN TONG 廖民堂 (97052370)

TSANG WAI KEE 曾偉基 (97047010)