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The Earth andThe Material World
Module 2
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Internal Structure of
the Earth
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Earth’s Internal Structure
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Earth’s Internal Structure (pp. 294-295)
Layer Name Main Characteristics
Crust Layer is solid. Its thickness varies:- 5-10 km beneath oceans (oceanic crust)- 30-65 km beneath continents (continental crust)
Mantle Upper mantle (or asthenosphere)
• Can be up to 670 km thick• Layer is semi-fluid. Made of partially melted rock.• Layer causes continental drift (plate tectonics).
Lower mantle • Layer is solid – very hot with high pressure.• Mainly made of silica, oxygen, iron and magnesium.
Core Outer core • Layer is liquid.• Layer gives rise to the Earth’s magnetic field.• Approximately 2270 km thick.
Inner core • Layer is solid – extremely hot with extremely high pressure.
• Approximately 1216 km thick.
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Like an egg…Shell Crust
(ALBUMEN)
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Biosphere
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Biosphere (pp. 295-296)
• The biosphere is all the regions in which life can exist on Earth.
• Composed of three parts:– Atmosphere (air)– Hydrosphere (water)– Lithosphere (land)
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Atmosphere
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Atmosphere
Composition
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Atmosphere (pp. 296-300)
• 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.
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Ozone Layer
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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.
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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.
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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.
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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).
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The Ozone Layer
• The 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.
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Hydrosphere
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Hydrosphere
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Hydrosphere (pp. 302-303)
• 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.
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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.
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Distribution of Water on Earth
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So, what’s the big deal?
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Another look
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Water CycleWater on Earth is constantly being
recycled.
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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 end
There are 4 main steps in the water cycle:
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1. Evaporation
• Evaporation: Liquid water becomes water vapor.
• Evapotranspiration: Living things produce water vapor through respiration and transpiration.
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2. Condensation:
Water vapor is cooled down and becomes liquid water.
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3. Precipitation:
Small water droplets in clouds gather and become rain drops which gravity pulls to the ground.
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4. Return to ocean
• Runoff: Water on mountains and on hills reaches waterways because of height differences.
• Infiltration: Water can seep to underground lakes and make its way back to the ocean.
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Lithosphere
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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.