UNIT: THE EARTH AND THE EARTH’S RELIEF: 1.- PARTS OF THE EARTH: Most of our planet is formed by the GEOSPHERE, that is a great rounded mass of rock, with a diameter of 13,000 km. It has got three layers: crust, mantle and core. It is covered by the HYDROSPHERE, that is the water from the oceans, seas, lakes, rivers, underground water, and ice in the mountains and in the poles. And finally, wrapping everything is the ATMOSPHERE, the gas layer composed by air and water steam. 2.- THE GEOSPHERE: It is formed by rocks. A rock is a natural material, hard and dense formed by chemical substances called minerals. Some rocks are formed only by one mineral (calcite), and others are formed by several minerals (granite: quartz, feldspar and mica). There are rocks that make up the continents and the bottom of the oceans in the crust, but they also form the mantle and core with some specific characteristics: they are very hot (about 5,000 ºC), they are very dense, and sometimes they are melted (magma) 3.- TECTONIC PLATES: The LITHOSPHERE is made up of the crust and the upper mantle. It’s formed by plates like tiles on the floor (Tectonic plates). These plates are 100km thick, and they can move very slowly from to another by forces in the mantle, because the mantle is formed by melted rocks. They can move only a few cm a year, but they touch, push or separate from each other, and the result of these movements is called: ‘CONTINENTAL DRIFT’. This theory says that millions of years ago all continents were joined as one called Pangea. Later this continent broke into two continents: Laurasia and Gondwana, separated by the Tethys Ocean. After that, North America separated from Europe, and South America from Africa. India and Australia moved to their actual places. These movements are still happening in the present, so in some millions years the Earth will be different than the one we know today.
4.- HOW THE EARTH’S RELIEF CHANGES: The shape of the crust has been changing for millions of years. The relief of the Earth is formed by the landforms (rivers, mountains, valleys…) on the Earth’s surface and forms landscapes… There are two elements that make changes on the relief: 1.- Geological Processes: changes made by the energy inside the Earth. Continental migration forms volcanic eruptions, earthquakes, mountain ranges, oceans… 2.- Erosion processes: changes by elements from the outside of the Earth, like water, wind and living beings. 4.1 GEOLOGICAL PROCESSES: A.1. GREAT MOUNTAIN RANGES: They are formed when two tectonic plates push each other (Himalayas, Andes…), or when two tectonic plates separate one from another, then magma arise from inside the Earth and form Mid-ocean Ridges.
A.2. VOLCANOES: They are located on the tectonic plates’ edges. A volcano is an opening, in a planet's surface or crust which allows hot magma, volcanic ash and gases to escape from below the surface. The magma is a mixture of molten rocks, gases and solids under the surface of the Earth, it can be about 2,000 ºC. When it goes up, it can melt rocks near the crust and get to the exterior, forming a volcano. The magma is in the magma chamber, and when it’s expelled is called lava. The lava goes up through the crack called a vent, and gets out through the crater, and when it solidifies, forms the volcanic cone.
A.3. EARTHQUAKES: They are also located on the tectonic plates’ edges. An earthquake is the result of a sudden release of energy in the Earth’s crust that creates seismic waves. The earthquake has got some elements: .- Hypocenter or focus is the point where the energy stored in the rock is first released, marking the point where it begins to rupture. .- Epicenter: is the point on the Earth’s surface that is directly above the hypocenter or focus. When the earthquake is located in the sea, it’s called a seaquake, and forms very destructive waves in the water called tsunamis. 4.2. EROSIONAL PROCESSES: The main elements that erode the surface on Earth are water, wind, ice, living beings… Steps of the erosion process: 1.- Weathering: is the breakdown of rocks at the Earth’s surface, by the action of rainwater, extremes of temperature, and biological activity. 2.- Erosion: breakdown and removal of rock materials by flowing water, wind, or moving ice. 3.- Transport: movement of sediments by water, wind or glacier ice to different places. 4.- Deposition: is the laying down of sediment carried by wind, water, or ice. Sediment can be transported as pebbles, sand & mud, or as salts dissolved in water. They are deposited in lower places, like the mouths of rivers or the sea.
The wind can transport tiny particles thousands of kms away. Rivers can erode landscapes forming valleys (V shape), and transport materials to the sea. Waves in the sea transport pebbles and sand. They form beaches and cliffs. Ocean currents transport and deposit sand along the coast and on the bottom of the sea. Glaciers are like rivers of ice, and they transport rocks and form valleys (U shape).
5.- MAIN LANDFORMS: We can find different landforms: plains, plateaus, mountains, ranges, valleys, depressions, beaches, capes, gulf. 1.- Plain is a piece of land that has no great changes in elevation. 2.- Plateau is a large area higher than surrounding land. 3.- Mountain is a very big natural elevation of the surface higher than a hill. 4.- Mountain ridge is a long, narrow chain of hills or mountains. 5.- Mountain range is a succession of mountain or narrowly spaced mountain ridges. 6.- Valley is a surface depression of the earth surrounded by hills or mountains. 7.- Depression is an area that is sunk below its surroundings. 8.- Cape is a point or body of land extending into a body of water, usually the sea. 9.- Bay is an area of water mostly surrounded by land. 10.- Gulf is a large bay that is an arm of an ocean or sea.
6.- ROCKS FROM THE CRUST: There are three types: Igneous rocks, sedimentary rocks and metamorphic rocks. a) Igneous rock: is formed through the cooling and solidification of magma or lava. Igneous rock may form below the surface (intrusive or plutonic rocks) or on the surface (volcanic rocks) b) Sedimentary rock: are formed by the deposition of material at the Earth’s surface and within bodies of water. Sedimentation is the name for processes that cause that mineral and/or organic particles form a rock. Particles that form a sedimentary rock by accumulating are called sediment. Sedimentary rocks are deposited in layers as strata. c) Metamorphic rock is the transformation of an existing rock type, in a process called metamorphism, which means "change in form". The previous type of rock changes increasing its heat and pressure, so it changes its form and characteristics. Examples: slate from Clay, marble from limestone, alabaster from gypsum. ROCK CICLE:
EARTH’S RELIEF:
VOCABULARY-GLOSARY:
Mass of rock: masa de roca
pole: polo
underground water: aguas subterraneas
to wrap:envolver
hard and dense: duro y denso
water steam: vapor de agua
calcite: calcite
several: algunos
quartz: cuarzo
to make up: formar
bottom: fondo
characteristics: características
to melt: derretir, fundir
tiles: baldosas
tectonic plates: placas tectónicas
melted rocks: rocas fundidas
separate ones from each others: separarse unas de otras
to push: empujar
to touch: tocar, rozar
were joined: estaban unidos
to break (broke): romper
Earth’s relief: relieve de la tierra
shape: forma
Landscapes: paisajes
migration: migración,
feldspar: feldespato
Continental Drift: Deriva Continental … still happening: todavía ocurriendo landforms: formas de relieve Geological processes: procesos geológicos
Earthquakes: terremotos
mountain range: cordillera
erosion processes: procesos de erosión
Wind: viento
living beings: seres vivos
to arise: levantarse
Volcano: volcán
located: localizada
Mid-ocean ridge: dorsal medio-oceánica
Opening: abertura
to allow: permitir
plate’s edges: bordes de placa
Below: debajo
mixture: mezcla
molten rocks: rocas fundidas
To expel: expulsar
crack: fisura, grieta
Magma chamber: cámara magmática
vent: chimenea volcánica
volcanic cone: cono volcánico
sudden: de pronto
to release: liberar
seismic waves: ondas sísmicas
hypocenter: hipocentro
to store: almacenar
to rupture: romper, desgarrar
epicenter: epicentro
above: sobre
seaquake: maremoto
to erode: erosionar
step: paso
weathering: meteorización
rainwater: agua de lluvia
removal: traslado
breakdown: rotura, descomposición
deposition: sedimentación
to lay down: depositar
to carry: llevar, transportar
pebbles: piedras
sand and mud: arena y barro
lower places: lugares más bajos
tiny particles: partículas muy pequeñas.
Valley: valle
features: rasgos, características, elementos
mouth of rivers: desembocadura de los ríos
waves: olas
ocean currents: Corrientes marinas
beach and cliffs: playa y acantilados
glacier: glaciar
plain: llanura
hill: colina
…is sunk below its surroundigs: …está hundida por debajo de los alrededores
cape: cabo
body of land: masa de tierra
body or water: masa de agua
bay: bahía
gulf: golfo
cooling: enfriamiento
strata: estrato, capa
increasing: incrementando
heat and pressure: calor y presión
slate: pizarra
clay: arcilla
marble: mármol
limestone: calcita
alabaster: alabastro
gypsum: yeso
plateau: meseta
range < ridge: cordillera<dorsal
LINKS TO LEARN MORE (BIBLIOGRAPHY and ACKNOWLEDGMENTS): http://www.revisionworld.com/gcse/geography/tectonic-activity/tectonic-plates?q=category/export/html/702 http://en.wikipedia.org/wiki/Cape_(geography) http://ieslamadraza.com/elena/websociales/geography3eso/relief/relief3.html