earth.ppthomepage.smc.edu/balm_simon/pdf/Astro/Astro2/earth_print.pdf · Rising sea levels due to...
Transcript of earth.ppthomepage.smc.edu/balm_simon/pdf/Astro/Astro2/earth_print.pdf · Rising sea levels due to...
10/11/2010
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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