Download Unit 2. EARTH`S RELIEF 1. THE EARTH

Unit2.EARTH’SRELIEF
1. THEEARTHSTRUCTURE
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Crust.ItisthemostexternalandthinnestlayeroftheEarth.
– Continental crust. It is composed by the emerged lands. It can
reach up to 20 or 70 km. Its main composition is based on rocks
andsands.
– Oceaniccrust.Itiscomposedbythelandthatissubmergedunder
thesea.Itonlyreaches10kmundertheoceans.
Mantle. It is mostly composed of magma (molten rock) and constitutes
the70%oftheEarth’sthickness.Itisnotarigidlayer.
Core.ItisthecentralpartoftheEarthandiscomposedofheavymetals,
iron,andnickel.Itisdividedinuppercoreandinnercore
2. ¿CÓMOSECONSTRUYEELRELIEVE?Pág32y33(castellano)
3. RELIEFEXTERNALAGENTS
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Thereliefchangesdueto:
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Erosion.Rockswearawayandtheydissolve.
Carriage:Itcarriesalltheerodedmaterialsfromtherocks.
Sedimentation:Itdepositsalltheerodedandcarriedmaterials.
Although the tectonic plates formed the relief there are other external
agentsthatmodifiesthereliefas:
1. Water
2. Wind
3. Temperatures
4. Vegetation
5. Humanbeings
1. Water: it is a constant action over the rocks. It can be stronger
dependingonthekindofstone(limestonecanbeerodedmoreeasily).
– Rain.Itcancreatevalleysandravines(barrancos).
– Rivers.Theyhavedifferentpartswheretheerosionchanges.Itis
harder in the upper course due to the slope and the speed of
waters. Instead it is very scarce is the lower course, since the
speedoftheflowismuchsmaller.
– Sea. Waves and currents cause different coastal geological
formationssuchascliffsorbeaches.
– Groundwater.Itcancausecavesandundergroundrivers.
• Rivers born in the mountains where form valleys and fluvial
terraces.
• Valleys:Theyhavebeencreatedbytheriversintheirflow
towards their mouth. They are usually low lands between
mountains.
Fluvialterracesareflatareaslocatedneartheriver
Groundwater.Itcancausecavesandundergroundrivers.
Glacier:frozenwaterformslakesinthemountains
1. The wind: It wears away the rocks and detaches some particles that
attack other rocks, polish and model them. It is called aeolian or wind
erosion. Dunes are the most typical formations created by aeolian
erosion.
2. Vegetation.Mostofthetimes,plantshelpfixsoilbuttheirrootscanalso
splitrocks.
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3. Humanbeings.Wetransformenvironmentforagriculture,stockbreeding,
cities,felling,reservoirs,fires,mining...
4. CONTINENTALRELIEF.
Thecontinentalreliefisthegeographicalformationswhichcoverthecontinents.
• Mountains.Theyareelevationsofthelandwithdifferentorigin.
– Theywerecreatedduringtheorogeniessomemillionsyearsago.
– The highest mountains emerged in more recent periods. Their
profilesaresteeper.
– The oldest mountains are lower and rounder. They are called
massifs.Theyusedtobehighbuttheywereeroded.
• Mountainrange:geographicalareacontainingnumerousmountains.The
mountainrangeisalsoknownasmountainsystem.
– The highest mountain range are the (Everest is the highest
mountainintheworld,8,848m).
– The longest mountain range is the Andes (together with Sierra
MadreandtheRockyMountains).
• Hill:smallmountain.
• Plateaux/Mesetas.Theyarelargeflathighareashigherthan400metres.
– ThehighestplateauxintheworldaretheTibetanPlateauandthe
Altiplano(Bolivia),theyexceed3,000metreshight.
• Plains. They are usually along the coast (coastal plains) or by the rivers
(riverplains).
• Valleys.Theyhavebeencreatedbytheriversintheirflowtowardstheir
mouth.Theyareusuallylowlandsbetweenmountains.
• Depressions: They are large areas located below sea level, such as the
Deadsea(-395m),DeathValley(-86m)ortheCaspianSea(-28m).
5. COSTALRELIEF:
Thecostalreliefiscomposedofseveraltypes:
• Beaches: They are geological landforms along the shoreline of an ocean,
sea, lake or river. It usually consists of loose particles which are often
composedofrock,suchassand,gravel,shingle,pebblesorcobblestones.
• Cliffs:theyareasignificantvertical,ornearvertical,rockexposure.
Baysandgulfs:Theyareareasofwatermostlysurroundedbyland.Gulfs
arebiggerthanbays.
• Capes:Theyarepointsorbodiesoflandextendingintoabodyofwater,
usuallythesea.
• Peninsula: piece of land that is bordered by water on three sides but
connectedtomainlandthroughanisthmus.
• Islands:Areaoflandcompletelysurroundedbywater.Ofthereisagroup
ofislandsitiscalledarchipielago
• Marshlands. They are a type of wetland that is subject to frequent or
continuousflood.
Elrelievedelosfondosmarinos.Pág37(castellano)
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