Transcript Core Unit 1: Patterns and Processes in the Physical

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Unit 1.1 Earth’s Structure
and the Tectonic Cycle
 Statement
 The mobility of the
earth’s crust produces
endogenic forces, which
give rise to geological
structures within it.
Crustal structures are
created, modified and
destroyed as part of the
tectonic cycle.
The Earth’s Structure
 Learning Objectives
 To understand the
internal structure of
the Earth.
 To understand the make
up of the planet.
 Knowledge and
understanding of key
concepts
Earth’s Crust
 Composed of two main
layers,
 Lithosphere Surface.
Hard, rigid and solid.
 Asthenosphere :
Semi- solid. Viscous
material capable of
flowing.
The Continental Crust or Sial
 Also called Sial due to
the large amounts of
silica and aluminium
present.
 5-10 Km Thick
 Lies on top of the
Lithosphere.
The Oceanic Crust
 Made up of older,
ancient rock like
basalt.
 Referred to as Sima
due to the presence of
silica and magnesium.
 Covers a larger area of
earth’s surface.
Plate Tectonics
Learning Objectives
 Be able to describe
the theory of plate
tectonics.
 Understand how
plates move
 Explain what happens
at the margins of
plates.
 Understand the
position of Ireland in
relation to plate
boundaries.
The World’s Ocean Floor
Plate Tectonics Theory
 There are several major
plates and several
smaller ones.
 Plates move as
passengers on the semi
molten asthenosphere.
 As plates move they
slide, diverge and collide.
 This movement gives rise
to earthquakes, volcanic
activity, sea floor
spreading and the
creation of ocean ridges.
How do the Plate’s Move ?
 Ans: Convection
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Currents !
Warm magma rises from
the interior of the
earth.
As it rises it cools and
falls again.
This process is repeated
and results in convection
currents that travel in
circular motions.
Consequently the plates
are moved causing
continental drift.
http://www.youtube.com/watch?v=xEYLx_bhtoA
Continental Drift
 The theory that the
continents moved was
first proposed by a
German Mathematician
Alfred Wegner in
1912.
 Wegner proposed that
200 Million years ago
all the continents
formed one
supercontinent called
Pangaea (Gk all the
land)
http://www.youtube.com/watch?v=cQVoSyVu9rk
Pangaea
Evidence for Continental
Drift
 Continental Fit
 Fossil Records
 Matching rock
records
 Matching Fossils
 Matching glacial
deposits
Sea Floor Spreading
 The theory of sea floor
spreading is that the
oceanic crust is widened
as new crust is created
along plate margins.
 Evidence: Rocks at the
centre of the ocean floors
have proven to be younger
than rock at the plate
margins.
Plate Margins
Plate Boundary Types
Locate on Map !
http://www.youtube.com/watch?v=hqp_TbIZU64
Convergent Boundaries
 Where Plates Collide.
 E.g. South American
and Nazca Plate.
 Associated LandformFold Mountains –The
Andes, Volcanic Activity.
 Rock is changed and
destroyed along these
destructive boundaries
in subduction zones.
Divergent Plate Boundaries
 Plates Move apart
 New rock is formed.
 These are therefor
constructive
boundaries.
 E.g. The American
plates and the African
Plates Creating the
Mid-Atlantic Ridge.
Conservative Boundaries
 Known as Transform
boundaries.
 Plates slip or slide past
each other.
 E.g San Andreas
Fault line. North
American and Pacific
Plates.
 Major Earthquake
Zone, Cascadia
Subduction
 Continental-Oceanic
 Oceanic –Oceanic
 Continental-
Continental
Oceanic –Oceanic
 Eurasian – Pacific Plate.
 The older heavier plate
is subducted underneath
the younger, lighter
plate.
 As the older plate
descends it is heated by
magma and friction and
is recycled into the
mantle.
 Island arcs, e.g Japan
rise from the ocean
floor as magma is
released resulting in
volcanic activity
Oceanic -Oceanic
Oceanic –Continental
Convergence
 The heavier oceanic plate is
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forced into the lighter
continental plate.
The oceanic plate is
subducted into the
asthenosphere where it is
melted back into the mantle.
This melting releases
upwelling magma resulting in
Volcanic Activity.
The lighter continental plate
is buckled upward to create
fold mountains .
Nazca and South American
Plates.
Oceanic – Continental
Convergence
Continental-Continental
 When continental
plates collide the
lithosphere subducts.
 Both plate remain
afloat but continue to
push into each other.
 As a result a wide
plateau of mountains is
created.
 E.g. The Himalayas
where the Indian and
http://www.youtube.com/watch?v=7gXixxYKM80
Eurasian Plates collide.
Continental-Continental
The formation of Ireland
 P 14
 You Tube
 http://www.youtube.co
m/watch?v=BE5nLCOih
7I
Key Concepts
 Lithosphere
 Subduction
 Asthenosphere
 Plateau
 Endogenic
 Pangaea
 Convection Currents
 Continental Drift
 Sea floor Spreading
 Conservative Boundary
 Divergent Boundary
 Transform Boundary