4 Earth’s Internal Structure (pp. 294-295) Layer NameMain CharacteristicsCrustLayer is solid. Its thickness varies:5-10 km beneath oceans (oceanic crust)30-65 km beneath continents (continental crust)MantleUpper mantle (or asthenosphere)Can be up to 670 km thickLayer is semi-fluid. Made of partially melted rock.Layer causes continental drift (plate tectonics).Lower mantleLayer is solid – very hot with high pressure.Mainly made of silica, oxygen, iron and magnesium.CoreOuter coreLayer is liquid.Layer gives rise to the Earth’s magnetic field.Approximately 2270 km thick.Inner coreLayer is solid – extremely hot with extremely high pressure.Approximately 1216 km thick.
10 Atmosphere (pp )Atmosphere is the envelope of gas that surrounds the Earth.Composition:Nitrogen (78%)Oxygen (21%)Carbon dioxide, Ozone, Water Vapour, Other gases (1%)Divided into 4 layers: Troposphere, Stratosphere, Mesosphere, Thermosphere.
12 Layers of the Atmosphere: Troposphere Up to 17 km thick near equator.7-8 km thick near north and south poles.Contains 80% of the atmosphere.Contains almost all the water vapour in the atmosphere (clouds, rain, etc).Drops approximately 6°C each kilometre.
13 Stratosphere Approximately 40 km thick. Above troposphere. Contains ozone layer.Absorbs ultraviolet rays.The farther from Earth, the higher the temperature.Large airplanes fly here.
14 Mesosphere Approximately 40 km thick. Third layer. Meteoroids catch fire and break up here.Air is very thin (molecules are scarce).Temperatures between -120°C and 27°C.
15 Thermosphere Over 90 km thick. Fourth and last layer. Contains polar auroras.Very hot (over 1000°C).Contains ionosphere (useful for communication systems).Burns up most meteoroids (shooting stars).
16 The Ozone LayerThe protective ozone layer has been shrinking in volume because CFC molecules and aerosol products are destroying it.CFC molecules are chlorofluorocarbon molecules found in refrigerators and air conditioners.When the ozone layer shrinks, it cannot protect us as well from solar UV rays.UV rays are trapped inside our atmosphere because of the greenhouse effect.
20 Hydrosphere (pp )The hydrosphere is formed by all bodies of water on the Earth’s surface.Some parts are: oceans, rivers, streams, lakes.Covers approximately 75% of the Earth’s surface.Water is essential for survival.
21 Distribution of Water on Earth Water is either fresh or salty.Fresh water can be found in lakes, ponds, and streams.Seas and oceans have salty water.Humans need fresh water to survive.
25 Water on Earth is constantly being recycled. Water CycleWater on Earth is constantly being recycled.
26 The Water Cycle The amount of water on Earth is constant. Water follows a cycle: it travels constantly between oceans, the atmosphere and solid ground.A cycle has no beginning and no endThere are 4 main steps in the water cycle:
33 The Lithosphere (p. 306 top only) Made of crust and part of upper mantle.70 km thick below oceans.150 km thick below continents.Essential for life:Provides minerals to plant roots.Offers habitat for animals.Contains oil and natural gas.Foundation for buildings.Constantly changing due to tectonic plate movement.
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