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Bulk Properties

Mass = 6 x 1024 kg

Diameter = 12,756 km

Density = 5515 kg/m3

(mix of rock and iron)

Acceleration due to gravity, a

Escape Velocity, ve

Another measure of gravitational strength

Minimum speed to escape the gravity of an object

Earth, ve = 11.2 km/s

AlbedoAmount of sunlight reflected back into

space

Earth’s albedo = 39%

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The Earth is the most complex terrestrial planet! The Earth is the most complex terrestrial planet!

surface

The Earth is the most complex terrestrial planet!

surface interior

The Earth is the most complex terrestrial planet!

surface

atmosphere

interior

The Earth is the most complex terrestrial planet!

surface

atmosphere

interior

magnetosphere

The Earth is the most complex terrestrial planet!

surface

atmosphere

hydrosphere

interior

magnetosphere

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The Earth is the most complex terrestrial planet!

surface

atmosphere

hydrosphere

interior

magnetosphere

biosphere

The Earth’s Interior

Seismic Waves – compression waves generated by earthquakes

Travel both along the surface and through the interior of the Earth

Seismic waves are refracted as they pass through the Earth

The Solid Inner Core of the Earth

Why does the Earth have an iron core?

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Chemical Differentiation

Earth was initially molten inside!

Source of heat: radioactivity and

impacts

Dense iron sank to center forming core

Less dense rock rose to surface

Explains density!

Earth formed solid crust as it cooled

* = radioactive heating

Magnetism is produced by the motion of charges

Field lines indicate presence of field

Magnetism in turn changes the motion of charges!

Electromagnetism!

Currents in the molten outer core

generates a magnetic field

Field is not aligned with geographical

poles

Charged particles from the Sun are swept round the magnetic field forming a magnetosphere

Some particles collect in the Van Allen Belts

Charged particles spiral along magnetic field lines and crash into the upper atmosphere causing it to

glow

Aurorae

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The Earth’s Surface

The Earth’s Crust (Lithosphere)

The lithosphere is made of rock

Rocks are made of mixtures of different crystals called minerals

Rocks are classified according to how they are formed

Igneous Rocks

From the cooling and solidification of molten rock

Two types: extrusive and intrusive

BasaltAn extrusive, dense, dark igneous rock from from

volcanoes on the Earth’s surface or the ocean floor. Most common igneous rock

GraniteAn intrusive igneous rock that made of large crystals of different minerals which give it its characteristic grainy

appearance

Sedimentary RocksMade from the accumulation and gradual compression of

sediments

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SandstoneSand deposited by wind

LimestonePrecipitation and deposition of Calcium Carbonate (CaCO3)

CoalOrganic material from decayed vegetation

Metamorphic RocksRocks transformed into new forms under high

temperatures and pressures beneath the surface of the Earth (not melted)

MarbleDerived from limestone (a sedimentary rock)

GneissDerived from granite (an igneous rock)

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A Pile of Schist!

A metamorphic rock!

The Rock Cycle

Plate Tectonics

Plates float on molten rock below (asthenosphere)

Continental Drift

Continents fit together like puzzle pieces

Conclusion: continents have moves relative to

each other

The geography of the Earth has changed greatly over its history!

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Continental Drift

Plate motion is driven by convection currents in the Earth’s mantle

There are two types of crust

29% continents

Subduction

Collision between oceanic and continental crust

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The Andes Mountains Seafloor Spreading

Separation of oceanic crust

The Mid-Atlantic Ridge The Himalayas

Collision of continental crust

Rift Valleys

Separation of continental crust

The East African Rift

Zone

Boundary FaultsPlates slide past each

other

Example:

West coast of USA

Mountain ranges, volcanoes and seismic

activity

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Not all earthquakes and volcanoes occur near plate boundaries!

Hot Spot Volcanism

Lava escapes under hot spots in the crust producing shield volcanoes

Example: Hawaiian Islands

Plate movement produces chains of volcanic islands

The Earth’s Atmosphere

Gases trapped by gravity

Chemical Composition

78.08% molecular nitrogen (N2)

20.95% molecular oxygen (O2)

0.934% atomic argon (Ar)

0.0314% carbon dioxide (CO2)

Observation:

Oxygen is very chemically reactive and should be destroyed as soon as it forms!

Conclusion:

It must be constantly being replenished!

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Where does the oxygen come from?

Photosynthesis by plants and bacteria

CO2 + H2O → carbon compounds + O2↑

The Food Chain

Carnivores/Omnivores

Herbivores

Plants

Why are the carbon dioxide levels so low?

71% Oceans

The Carbon Dioxide Cycle

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The Population Explosion

Need for energy and use of fossil fuels rapidly increasing!

Reverse Photosynthesis

carbon compounds + O2 → CO2↑ + H2O

Removes O2 and releases CO2!

Burning of Fossil Fuels for Energy!

e.g. coal, oil, gas, wood, gasoline etc

Other factors

Deforestation Pollution

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Reduces Earth’s ability to remove CO2 from the atmosphere!

Result?

Rising CO2 Levels!

Why be concerned about rising CO2 levels?

The Greenhouse Effect

CO2 traps heat in the atmosphere and raises surface temperatures!

The Greenhouse Effect is vital!

Without it, the Earth would be over 50 ºF colder and much less habitable!

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Global Warming

Gradual warming of the Earth’s surface due to rising CO2 levels

Global Warming

Effects of Global Warming

Global climate change

Rising sea levels due to melting of polar ice caps

Solution?

Reduce use of fossil fuels and rely more on alternative energy sources!

Problem:

Difficult politically!

The Layered Structure of the Earth’s Atmosphere

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Troposphere

• lowest, thickest part of atmosphere extending up to 12 km from the surface

• all weather occurs here, driven by convection

• atmospheric pressure, P = force exerted by atmosphere above

• Psea level = 14.7 lbs/in2 = 1 atmosphere (atm)

• pressure and temperature decrease with altitude

Stratosphere – home of the ozone (O3) layer

Extends from 12-50 km above the surface

Ozone Depletion

Partial destruction of the ozone layer by chemicals (CFC’s) released into the atmosphere

Result: higher UV radiation levels at surface

Ozone Depletion is NOT Global Warming!

Temperature increases with altitude in the stratosphere due to absorption of radiation by

ozone

Pressure continues to decrease

Mesosphere

• layer above the stratosphere

• above ozone layer so not heat absorbed

• temperature and pressure decrease with altitude

Thermosphere/Ionosphere

• highest, thinnest layer beginning at 80 km above surface

• atmospheric molecules broken down and ionized by short wavelength radiation (ionosphere)

• absorption of radiation causes temperature to increase with altitude (thermosphere)

• pressure continues to decrease, merging into interplanetary space

• thickness expands and contracts with the solar cycle

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Tides

Daily ocean level changes

2 high and 2 low tides per day

The Earth rotates through the tidal bulge

Spring Tides – gravity of Sun and Moon combine at new and full moon

Higher than average tides

Neap tides – gravity of Sun and Moon partially cancel at

quarter moons

Lower than average tides

Other Tidal Effects