ch videos and take notes.
http://www.youtube.com/watch?v=kNc8NTiisUM&feature=related
http://www.youtube.com/watch?v=JTgbjLMwUEM&feature=relmfu
(landforms
parts 1 and 2)
http://www.youtube.com/watch?v=i3c3t3bi2aI&feature=endscreen&NR=1
landforms definitions.
Make a mind map with concepts from videos.
http://www.youtube.com/watch?v=Y7EO4ygqyIU&feature=autoplay&list=PLF9293CDDD9E49786&playnext=2
(erosion)
On maps locate (draw) the main world and Mexico´s
relief.
RELIEF
The
relief (or terrain) is the different shapes that the surface of the Earth has
adopted over millions of years. It can divided into continental (surface
relief) and oceanic (submarine relief).
The
relief is the result of internal internal forces, which form it and external
forces, which transform it.
CONTINENTAL RELIEF
•Mountains:
elevations of the terrain above the surrounding land with steep slopes or sides
and an altitude of more than 600 metres. When they are together in “rows” they
are knows as sierras or mountain ranges, as the Himalayas (Asia), that is the
world’s highest one.
•Valleys:
are areas of low land between mountains. Rivers flow through many valleys.
•Plains:
low, flat areas of land., no higher than 200 metres above sea level. They are
formed by large rivers.
•Plateaus:
large plains raised more than 200 metres above sea level. The highest plateaus
are the Tibetan High Plateau (Asia) and the Bolivian (South America).
•Basins
(or depressions): sunken or drepressed areas below the surrounding areas. Some
are below sea level .
COASTAL RELIEF
Coastal
relief: coasts are where the continents meet oceans and seas. The coastal
relief forms are:
•Peninsula:
an area of land surrounded by water on all sides except one.
•Isthmus:
connects a peninsula to a continent.
•Cape:
part of the coast which extends into the sea
•Gulf:
a large area of sea or ocean partially enclosed by land. A bay is a small gulf
•Island:
an area of land surrounded by water on all sides
•Archipelago:
is a group of islands
•Beaches:
flat coastal area with sand or stones.
•Cliffs:
high coastal area with steep rock formations.
•Estuary:
area formed when the sea flows into de mouth of a river
•Fiord:
strip of sea that comes into the valley of a river / land between high cliffs.
OCEANIC RELIEF
• Continental
shelf: is the extension of the continents under the seas or oceans. They are
vast plateaus which reach a depth of 150-200 metres.
•Continental
slope: is a steep incline found between the continental shelf and the abyssal
plain.
•Abyssal
plains: are large flat areas of the deep ocean floor (4,000 or 5,000 metres
below sea level). In them we can find:
•Oceanic
ridges: large mountain ranges that rise up 3000 metres from the ocean floor.
Some of the highest peaks rise above the surface and form islands such as the
Hawaiian Islands.
• Oceanic
trenches: are large, deep depressions in the ocean floor. The deepest one is
the Challenger Deep (11000 metres) in the pacific Ocean.
HOW THE RELIEF IS FORMED?
Continental drift
In
1912 Alfred Wegener developed the continental drift theory. According to it,
there was only one continent, which broke up millions of years ago. This
continent was called Pangea
Tectonic plates
The
Earth’s crust is divided into different plates called tectonic plates. They are
in continous movement (speed of two to ten centimeters per year).
Some
plates from move apart letting the magma come out. Some other plates collide,
creating folds when the terrain is flexible or faults when it is extremely
rigid. Also, the collison of plates has produced many mountains, such as the
Himalayas range which is still rising.
The
movement of tectonic plates can produce volcanoes and earthquakes:
•A
volcano is an opening in the surface of the Earth through which very hot rocks,
magma comes out. When magma is outside the volcano it is called lava. Volcanoes
are generally found on the edge of tectonic p lates.
•Earthquakes
are also caused by plate tectonics; when two plates crash, the ground vibrates.
This vibration is called an earthquake. When the crashing is on the ocean floor
the earthquake can produce waves called tsunamis.
HOW
IS THE RELIEF TRANSFORMED?
External
forces shape the relief. This transformation involves three types of action:
• Erosion:
is the fragmentation and dissolution of rocks, soil and mud.
• Transportation:
eroded materials are transported by wind or water.
• Sedimentation:
is the accumulation of sediments such as mud, sand or mud.
There
are four main agents of erosion: temperature, water, wind and living things.
1. Temperature: abrupt changes in it can
break rocks. It happens in mountains or deserts, where there is a great
difference between daytime and night time temperatures.
2. Water:
◦ When
it infiltrates through rocks and freezes, water expands and breaks the rocks.
◦ Solution
is when water dissolves some kinds of rocks, such as limestone producing caves.
◦ Fluvial
erosion: In the upper course the river erodes materials creating deep valleys
and canyons/ In the middle course the slopes are gentler and rivers transport
the eroded materials/ In the lower course, near the sea, land is flat and water
deposit sediments on the river´s banks forming alluvial. plains.
◦ Marine
erosion: waves and currents wear away coasts creating cliffs. Sediments
transported by the sea water are deposited and form beaches.
3. Wind: transports particles of sand or
soil from their original place and deposites them. Sand dunes are formed this
way.
4. Living things: Plants and animals
transform the relief through their activities./ Human beings make the fastest
and more dangerous impact through activities such as farming, mining,
deforestation, building roads, tunnels or reservoirs.
