The Earth andThe Material World

Module 2

Internal Structure of

the Earth

Earth’s Internal Structure

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.

Like an egg…Shell Crust

(ALBUMEN)

Biosphere

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)

Atmosphere

Atmosphere

Composition

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.

Ozone Layer

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.

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.

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.

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).

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.

Hydrosphere

Hydrosphere

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.

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.

Distribution of Water on Earth

So, what’s the big deal?

Another look

Water CycleWater on Earth is constantly being

recycled.

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:

1. Evaporation

• Evaporation: Liquid water becomes water vapor.

• Evapotranspiration: Living things produce water vapor through respiration and transpiration.

2. Condensation:

Water vapor is cooled down and becomes liquid water.

3. Precipitation:

Small water droplets in clouds gather and become rain drops which gravity pulls to the ground.

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.

Lithosphere

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.