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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)
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