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1. PLATE TECTONICS.
1. PLATE TECTONICS.
1. The internal structure of the Earth.
The Earth is made
up of 3 main layers:
Core
Mantle
Crust
Mantle
Outer core
Inner core
Crust
1. PLATE TECTONICS.
1. The internal structure of the Earth.
The interior of the Earth can be divided into layers according
to two criteria: its chemical composition and its physical
state.
Compositional layers:
CRUST: made up of less dense rocks, rich in silicon and
aluminium.
Continental crust is the layer of rocks
which forms the continents.
Oceanic crust is thinner than
continental crust.
1. PLATE TECTONICS.
1. The internal structure of the Earth.
The interior of the Earth can be divided into layers according
to two criteria: its chemical composition and its physical state.
Compositional layers:
MANTLE: made up of denser rocks like peridotite and
magnesium.
1. PLATE TECTONICS.
1. The internal structure of the Earth.
The interior of the Earth can be divided into layers according
to two criteria: its chemical composition and its physical state.
Compositional layers:
CORE: made up of iron.
1. PLATE TECTONICS.
1. The internal structure of the Earth.
Physical layers.
LITHOSPHERE: is the rigid surface layer.
ASTHENOSPHERE: is the area under the lithosphere where the mantle is
ductile and is partially molten in some places.
LOWER MANTLE: solid but still flexible and ductile.
CORE: consists of a molten outer layer and a solid inner part.
1. PLATE TECTONICS.
1. The internal structure of the Earth.
Video 1.
1. PLATE TECTONICS.
1. The internal structure of the Earth.
The melting point of materials inside the Earth increases with
depth, because of the pressure, which means that iron, which
melts at 1550 C on the surface, is found in a solid state in the
centre of the Earth at a temperature of 6000 C.
1. PLATE TECTONICS.
1.2 Seismic discontinuities.
There are two types of internal seismic waves:
•Primary waves (P): are the fastest and the first to reach the surface.
They move through solids and liquids.
1. PLATE TECTONICS.
1.2 Seismic discontinuities.
There are two types of internal seismic waves:
•Secondary waves (S): are slower and are registered after primary
waves. They only move through solids.
As the outer core of the Earth is liquid, the S-waves stop when they reach it.
1. PLATE TECTONICS.
1.2 Seismic discontinuities.
There are two discontinuity BOUNDARIES:
•The Mohorovicic discontinuity: marks the boundary between the crust
and the mantle. This boundary is 30-40 km below the continents and
less than 10 km under the ocean.
•The Guttenberg discontinuity: at a depth of around 2900 km. This
boundary marks the limit between the mantle and the molten layer of
the Earth´s outer core.
1. PLATE TECTONICS.
1.2 Seismic discontinuities.
There are two discontinuity BOUNDARIES:
1. PLATE TECTONICS.
ACTIVITIES. PAGE 11.
1-6.
1. PLATE TECTONICS.
WHAT METHODS DO SCIENTISTS USE TO INVESTIGATE THE
COMPOSITION OF THE EARTH´S INTERIOR?
DRILLING.
I WANT YOU TO FIND OUT INFORMATION ABOUT THIS (HOMEWORK)
1. PLATE TECTONICS.
WHAT METHODS DO SCIENTISTS USE TO INVESTIGATE THE
COMPOSITION OF THE EARTH´S INTERIOR?
SEISMIC WAVES.
Because different types of seismic waves behave differently when
they encounter material in different states (for example,
molten or solid), seismic stations established around Earth detect
and record the different types of waves
Geologists use these records to establish the structure of Earth's
interior.
2. THE MOVEMENT OF CONTINENTS.
Key words.
Controversy = controversia.
Join = unir.
Slide = deslizar.
Land-based = terrestres.
Continental shelf = plataforma continental.
Glacial moraine = morrena glacial.
2. THE MOVEMENT OF CONTINENTS.
Some scientists believed that the position of continents was fixed,
while others proposed that they had moved great distances over long
periods of time.
WHAT IS YOUR OPINION? Discuss with your
classmate for 3 minutes.
2. THE MOVEMENT OF CONTINENTS.
ALFRED WEGENER AND THE CONTINENTAL DRIFT THEORY.
1) Wegener noticed that the coasts of western Africa and eastern
South America looked like pieces of a jigsaw puzzle
(GEOLOGICAL EVIDENCE).
2. THE MOVEMENT OF CONTINENTS.
ALFRED WEGENER AND THE CONTINENTAL DRIFT THEORY.
2) He knew that the two areas had many geological and biological
similarities. Identical fossils of land-based organisms such as
reptiles and plants were situated far apart. These organisms could
never crossed the oceans that now separate them.
(PALAEOLITHIC EVIDENCE).
2. THE MOVEMENT OF CONTINENTS.
ALFRED WEGENER AND THE CONTINENTAL DRIFT THEORY.
3) The continents which were situated in the South Pole of
Pangaea have glacial moraines from the same age
(PALAEOCLIMATIC EVIDENCE ).
A moraine is any accumulation of rocks that occurs in glaciated
regions on Earth
2. THE MOVEMENT OF CONTINENTS.
ALFRED WEGENER AND THE CONTINENTAL DRIFT THEORY.
2. THE MOVEMENT OF CONTINENTS.
ALFRED WEGENER AND THE CONTINENTAL DRIFT THEORY.
According to his theory, the continents made of lighter crust, slid
over a continuous thicker layer. This layer made up the ocean
floor and continued under the continents. He proposed that
around 200 million years ago, all the continents were joined as
one. He called this PANGAEA “THE WHOLE EARTH”.
2. THE MOVEMENT OF CONTINENTS.
ALFRED WEGENER AND THE CONTINENTAL DRIFT THEORY.
At first, other scientists did not accept Wegener’s theory of
continental drift. But scientists now know that the continents rest
on massive slabs of rock called tectonic plates. The plates are
always moving and interacting in a process called plate tectonics.
2. THE MOVEMENT OF CONTINENTS.
VIDEO 2. CONTINENTAL DRIFT THEORY.
https://www.youtube.com/watch?v=Np9ADpKnBSY
1. PLATE TECTONICS.
ACTIVITIES. PAGE 11.
7-9.
3. THE THEORY OF PLATE TECTONICS.
3.1 SEISMIC AND VOLCANIC BELTS.
-In the second half of the 20th century, seismometers were set up all
over the world.
-These showed that earthquakes were located in narrow bands, called
seismic belts.
-Seismic belts are characterised by the same types of landforms.
3. THE THEORY OF PLATE TECTONICS.
3.2 LITHOSPHERIC PLATES.
A lithospheric plate is a fragment of the lithosphere. Each plate is
separated by a seismic belt.
Classified according to two criteria:
SIZE.
TYPE OF LITHOSPHERE:
-Oceanic plates (composed of oceanic lithosphere).
-Continental plates (composed of continental lithosphere).
-Mixed plates (composed of both oceanic and continental lithosphere).
3.3 TYPE OF PLATE BOUNDARIES.
•DIVERGENT BOUNDARIES (CONSTRUCTIVE). Two plates move apart to
create a new ocean lithosphere. Example: the Mid-Atlantic Ridge.
At divergent boundaries new crust is created as two or more
plates pull away from each other. Oceans are born and grow
where plates diverge or pull apart.
3.3 TYPE OF PLATE BOUNDARIES.
•DIVERGENT BOUNDARIES (CONSTRUCTIVE). Two plates move apart to
create a new ocean lithosphere. Example: the Mid-Atlantic Ridge.
•DIVERGENT BOUNDARIES (CONSTRUCTIVE). Two plates move apart to
create a new ocean lithosphere. Example: the Mid-Atlantic Ridge.
Icelandic Volcanism and Plate Tectonics
https://www.youtube.com/watch?v=QrQDXnnXOo4
3.3 TYPE OF PLATE BOUNDARIES.
•CONVERGENT BOUNDARIES (DESTRUCTIVE). Zones where two
continents collide or subduction zones where the ocean floor goes into
the mantle. Example: Mariana Trench in the Pacific Ocean.
You are going to see a trench instead of a ridge.
3.3 TYPE OF PLATE BOUNDARIES.
•TRANSFORM BOUNDARIES (PASSIVE). Two plates slide horizontally
against each other. Example: The San Andrés fault is an example of a
transform boundary and is responsible for the earthquakes that affect
the California area.
3.3 TYPE OF PLATE BOUNDARIES.
•TRANSFORM BOUNDARIES (PASSIVE). Two plates slide horizontally
against each other. Example: The San Andrés fault.
3.4 SUBDUCTION ZONES.
Subduction occurs at trenches when an ocean collides with another
plate and is forced down into the mantle.
•Subduction under the continental lithosphere. This occurs when the
trench is next to the boundary of a continent. As a result of compression
and volcanic activity, an Andean mountain range is formed.
3.4 SUBDUCTION ZONES.
Subduction occurs at trenches when an ocean collides with another
plate and is forced down into the mantle.
•Subduction under the oceanic lithosphere. This creates an arc of
volcanic islands. Many Pacific island arcs and some Atlantics arcs have
formed as a result of this process.
3.5 MAIN CONCEPTS.
1.THE LITOSPHERE IS DIVIDED INTO GREAT BLOCKS, CALLED PLATES,
WHICH COVER THE SURFACE OF THE EARTH AND FIT TOGETHER LIKE A
JIGSAW.
3.5 MAIN CONCEPTS.
2.
MOST OF THE EARTH´S INTERNAL GEOLOGICAL ACTIVITY
HAPPENS AT THE BOUNDARIES OF THE PLATES.
3.5 MAIN CONCEPTS.
3.
THE OCEAN FLOOR IS CONTINUALLY GENERATED ALONG THE
RIDGES AND IS DESTROYED BY SUBDUCTION IN THE TRENCHES.
3.5 MAIN CONCEPTS.
4.
WHERE THE PLATES SEPARATE, NEW OCEANS ARE CREATED.
WHERE THEY COLLIDE, MOUNTAIN RANGES ARE LIFTED UP.
4. THE OCEAN.
4. 1 THE OCEAN FLOOR.
oLANDFORMS. Maps of the ocean have been created using sonar.
Sonar (Sound Navigation And Ranging) is a technique that
uses sound propagation (usually underwater) to navigate,
communicate with or detect objects on or under the surface of the
water. Active sonar is emitting pulses of sounds and listening for
echoes.
•http://www.youtube.com/watch?v=-fAAxEIFeLU
(Scientists "See" Ocean Floor via Sonar)
Scientists use cameras and sonar near the U.S. Virgin Islands to
"see" the seafloor and find out how fish and other sea life use the
underwater habitats.
4. THE OCEAN.
4. 1 THE OCEAN FLOOR.
oLANDFORMS. Maps of the ocean have been created using sonar.
-Mid-ocean ridge. This is an enormous mountain range more than
60000 km long and up to 2000 km.
World Distribution of Mid-Oceanic Ridges.
4. THE OCEAN.
4. 1 THE OCEAN FLOOR.
oLANDFORMS. Maps of the ocean have been created using sonar.
-Trenches. These are narrow, deep channels which are usually found
next to continental boundaries or next to volcanic islands arcs.
4. THE OCEAN.
4. 1 THE OCEAN FLOOR.
oCOMPOSITION. The ocean floor is made up of volcanic rocks that are
covered in marine sediment.
Homework: Page 15, number 10.
4. THE OCEAN.
4. 2 Sea-floor spreading.
Seafloor spreading is a process that occurs at mid-ocean ridges, where
new oceanic crust is formed through volcanic activity and then
gradually moves away from the ridge.
As the time passes, the ocean floor spreads and extends.
WHILE OCEANIC LITHOSPHERE IS CONSTANTLY BEING FORMED AT THE
RIDGES, IT IS ALSO CONTINUALLY BEING DESTROYED AT THE
TRENCHES.
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Page 17: 13, 14, 15, 19.
5. THE MECHANISMS BEHIND THE PLATE TECTONICS.
5.1 WILSON CYCLE.
The Canadian geologist, Wilson, suggested that there have been two
cyclical processed of RIFTING AND REUNITING of supercontinents
during Earth´s history.
5. THE MECHANISMS BEHIND THE PLATE TECTONICS.
CONTINENTAL RIFTING.
EXAMPLE: RIFT VALLEY IN EAST AFRICA.
5. THE MECHANISMS BEHIND THE PLATE TECTONICS.
CONTINENTAL RIFTING.
Magma rises up through these fractures as lava. The rift has caused
depressions, which has resulted in the formation of deep lakes at the
bottom of the valley.
5. THE MECHANISMS BEHIND THE PLATE TECTONICS.
EXTENSION OF THE OCEAN BASIN.
The Atlantic is an example of an expanding ocean. Its size is increasing.
5. THE MECHANISMS BEHIND THE PLATE TECTONICS.
5. THE MECHANISMS BEHIND THE PLATE TECTONICS.
CLOSING OF THE OCEAN BASIN.
The oceanic lithosphere becomes progressively older the further it is
from the ridge. It also becomes colder and denser. This causes the
lithosphere to move down into the mantle. The ocean is starting to
shrink. This is the situation in the Pacific Ocean.
5.3 GLOBAL TECTONICS.
Plate tectonics is also known as global tectonics because it explains the
relationship between many geological phenomena:
•Volcanic activity.
•Earthquakes.
•The distribution of continents and oceans in space and time.
•The formation and destruction of the ocean floor.
•The location of mineral deposits and fossil fuels.
DEVELOPMENT OF BASIC COMPETENCES
Page 23.