GEOGRAPHY

2. 1. THE EARTH’S CRUST.
A) The earth’s structure.
 The Earth is a rocky, almost spherical planet divided into three concentric
layers:
① The core consists of the inner core and
the outer core (molten materials).
② The mantle is made up of materials
such as molten rock or magma.
③ The crust is a layer of solid rock
such as basalt or granite. The outer
part of the crust is the lithosphere.
 The Earth’s temperature increases with depth.
 The activity inside the Earth can be seen on the Earth’s crust, because this
produces different types of relief.

3. B) Oceans and continents:
 71% of the Earth’s surface is covered by water.
 29% or the Earth’s surface is the dry land of the continents.
 Continents: are very large land masses surrounded by oceans and seas.
• Asia
• America
• Africa
• Antarctica
• Europe
• Oceania.
 Oceans: are vast masses of saltwater that are connected to each other.
• Pacific Ocean (largest and deeptest).
• Atlantic Ocean (2nd largest).
• Indian Ocean.
• Southern Ocean (frozen so much of the year).
• Artic Ocean (mainly frozen, the smallest).

7. 2. WHAT IS THE EARTH’S RELIEF?
Relief: Consisting of all the features, such as the mountains and
valleys,
which make the terrain so varied (watch the vocabulary
presentation!!!)
a) Continental relief:
 Mountains
(mountain ranges)
 Valleys
 Plains
 Plateaus
 Basins
b) Coastal relief:
 Cliffs
 Beaches
 Peninsula
 Isthmus
 Cape
 Island
 Gulf
 Bay
c) Ocean floor ’ s
relief:
 Continentel shelf
 Continental slope
 Abyssal plains
 Mid-ocean ridges
 Ocean trenches

8. 3. INTERNAL FORCES OF RELIEF.
 THEORY OF CONTINENTAL DRIFT:
 Many million years ago there was only a single super-continent, called
Pangaea, which broke up into fragments to make the continents we have
today.
 Look at the coasts of the current continents, we can see that they seem
to match like an enormous jigsaw.

9. PANGAEA AND CONTINENTAL DRIFT.

10.  TECTONIC PLATES:
 The Earth’s crust is not just one big piece of rock. It is divided into smaller pieces of
crust called tectonic plates.
 The plates move because the mantle underneath them is moving, but they only
move very slowly.
 The places where the plates meet are called plate boundaries or plate margins.

11. WHAT HAPPENS WHEN THE PLATES MOVE?
 FAULTS AND FOLDS:
 Below the surface of the Earth, gases and compressed materials put
pressure on the crust. They can deform it or make it crack. They are
called INTERNAL FORCES.
 The Earth’s surface ondulates or fractures by the pressure from molten
materials in the mantle.
 When Earth’s surface ondulates FOLDS are created.
 When the surface is extremely ridig FAULTS are
created, and one block rise while the other sink.

12.  Fold:
• When two plates move towards each other the Earth’s surface is forced
upwards or folded.
• This happens very slowly.

13.  Faults:
• When the plates againts each other, pressure can build up. Sometimes
this causes the rock to split, making a fault in the rock.
• On one side of the fault, the ground rises, and on the other side it falls.

14.  VOLCANOES:
• A volcano is an openning in the surface of the Earth through which very hot
material (magma) comes out.
• When magma comes out of a volcano, it is called lava.
• Volcanic cones are the result of lava accumulating outside the opening.
• Volcanoes are generally found on the edge os tectonic plates because this is
the weakest part of the Earth’s crust.

16.  EARTHQUAKES:
• Sometimes the increase in pressure at a plate boundary can cause a release
of energy that makes the ground shake. This is called a earthquake.
• The point in the ground where the earthquake starts is called the focus or
hypocentre.
• Shock waves or seismic waves are vibrations that spread out from the focus.
• The epicentre is the point on the Earth’s surface above the focus.
• We measure the strength of an earthquake using the Richter Scale.

18.  TSUNAMIS:
• If earthquakes and volcanic eruptions happen in or near the sea, they can
displace sea water, and this causes a tsunami.
• A tsunami is a series of enormous waves.
• It can cause a lot of damage to coastal areas.
• TEDeD lesson:https://ed.ted.com/lessons/how-tsunamis-work-alex-
gendler#watch

20. Remember: the earth’s crust
 It is thicker where it forms the continents and thinner where the oceans cover
it.
 The crust is not smooth, there are features of land relief (mountains, valleys,
basins or depressions and plains) on land and under the sea.
 The Earth’s relief is constantly changing because of internal and external
forces.

21. HOW DOES RELIEF CHANGE?
o The Earth’ relief is shaped by its internal forces: pressures (the
movement of tectonic plates: folds and faults), volcanoes and
earthquakes.
o Relief is also shaped by external agents on the Earth’s surface
(external forces): water, wind, changes of temperature and living
things (human action).
o All of these external agents modify relief by three processes:
 Erosion: materials, such as rocks and soil, are broken up and moved
around by external agents.
 Transportation: these materials are then transported by seas, rivers,
ice or wind.
 Deposition: eroded rocks, sand and mud are deposited in low areas
where the sediments acumulate.

22. EXTERNAL FORCES OF RELIEF
o Water: plays a very important role in erosion, transport and deposition (rivers,
seas and oceans, rain water and ground water).

23. EXTERNAL FORCES OF RELIEF
o Wind: (aeolian erosion)
 Is when wind erodes and transports rocks and sand.
 It often occurs in dry climates, sucha as deserts, because there is little
vegetation to protect the soil.
o Changes of temperature:
 In deserts or mountainous areas it is much hotter during the day than at
night-time.
 Water sometimes enter the cracks in rocks. It may break the rocks if it
freezes and expands.
o Living things:
 Vegetation or animals.
 Human action: through activities such as agriculture, deforestaion or mining.
Roads or reservoirs are man-made features of the Earth’s relief.