The Home World: EARTH

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The Home WorldEARTH
a 1 AU
P 365 d
i (orb) 0o
e 0.017
Prot 1 d
i (rot) 23.5o
R 6378 km
M 6.0 x 1024 kg
r 5.5 g/cc
g 9.8 m/s2
vesc 11 km/s
A 0.37
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Near-Earth Space The Van Allen Belts
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Nature of the Belts

• Discovered early in the space age with a Geiger
  counter.
• Energetic charged particles are trapped in the
  Earths magnetic field.
• The inner belt contains protons, and the outer
  contains electrons.
• The inner belt begins at only 100 km or so above
  ground.

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Aurorae
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Space Aurora
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Aurora Borealis from Yellowknife in Canada
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Aurorae

• Solar wind particles are generally repelled by
  the magnetosphere, but some sneak into the
  atmosphere by running along magnetic field lines
  toward the poles. (Outer van Allen belt)
• Earth atmospheric particles sneak into the belts
  as well. (Inner van Allen belt)
• At 100km altitude, solar wind particles collide
  with atmosphere particles to produce an auroral
  light display.

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Comparison of Planetary Magnetic Fields
Equatorial Field (Gauss)
Mercury 0.002
Venus lt0.0003
Earth 0.305
Mars (0.0004)
Jupiter 4.2
Saturn 0.20
Uranus 0.23
Neptune 0.06-1.2
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The space around the Earth is not exactly
crowded, but there is a great deal of space
debris in orbit around Earth.
Space Debris
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The Kessler Syndrome
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The Earth at Night (issues of light pollution)
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Atmosphere Appearance of the Sky
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Understanding Sky Color
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Sky Color from Two Places
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Structure of the Earths Atmosphere
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Atmosphere Ozone Layer Component
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Antarctic Ozone Hole
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Ozone Destruction

• Ozone molecule O3
• O3 protects use from harmful solar UV radiation
• An efficient O3 destruction mechanism involves
  chlorofluorocarbons (CFCs Cl, F, C)
• ltchemistrygt
• A single Cl atom can be used 1000s of times to
  break up ozone molecules!

Catalyst process
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Ozone Trends
South Pole
North Pole
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Atmosphere and Surface Energy Budget of the
Earth
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Global Warming Trends and Effects

• The overall topic of global warming is
  complicated.
• Increased greenhouse gases (carbon dioxide,
  methane, etc)
• act like a blanket to block the escape of
  infrared heat light.
• The Earth has also undergone cycles in the past.
• The main concern is the impact and control of
  warming trends.

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Share Question

• The previous figure displayed information about
  sea ice area.
• Is area the best measure for the amount of
  ice?
• If so, why?
• If not, what would be better? And, why?

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Climate Considerations
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Weather

• Primarily driven by solar radiation.
• Other significant influences include
• Land mass and oceans
• Planet rotation
• Atmospheric composition
• Ozone
• Greenhouse effect
• Volcanic activity

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The Hadley Cell Fundamental circulation pattern
because of the fact that planets are round.
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Coriolis Deflection Planet rotation causes
north-south weather circulation to deflect
east-west.
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The Coriolis Force
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Hadley Cells on the Earth
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Volcanoes and Resurfacing

• Magma is less dense than rock, and so rises from
  the interior
• This breaks through, giving a volcano
• Products
• New rocks (esp. basalts)
• Ash ( 1mm )
• Cinders ( 1cm )
• The key point is that volcanoes lead to
  resurfacing and are evidence of an active
  planetary interior

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Mount St. Helens
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Tungurahua (Andes)
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Rock Types

• Igneous (ignusfire) - form from
  crystallization of molten rock
• Magma - molten inside earth
• Lava - molten on surface
• Of planetary interest
• Basalt - fast cooling
• Granite - slow cooling

• Sedimentary - formed by deposition of small
  particles which become cemented (e.g., sandstone,
  shales)
• Metamorphic - changed by heat, pressure, and/or
  chemistry (e.g., marble)

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Crustal Plates and Tectonic Activity

• Earths surface (or crust) is not a single solid
  piece, but consists of large and small plates
• These plates slowly drift around
• At points of convergence, get volcanoes, mountain
  ranges, and earthquakes

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Crustal Plates
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Long Term Plate Drifting
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Plate Motion
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Volcanic Activity on Earth and Relation to Motion
of Plates
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Recycling process and resurfacing effects
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Interior Structure of the Earth
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Detail of Earth Interior
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Share Question

• Earthquakes are an important tool for scientists
  because their vibrations
• a) influence the Earth's orbit about the Sun
• b) allow the study of the Earth's internal
  structure
• c) inform us of the mass of the Earth
• d) are used to predict the future of plate
  tectonics

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Seismology

• Study of the Earths interior from how it carries
  vibrations
• Types of vibrations
• P-waves pressure waves that travel like sound
• S-waves shear waves, like on a rope
• Terminology
• Focus point at which the earthquake originates
• Epicenter surface point above the focus
• Seismometer a device to measure P S waves and
  the strength of earthquakes

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Earthquake
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Wave Forms
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Refraction of traveling sound waves in the Earth
reveals its components
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Shuddering of the Earth
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Earths Magnetic Field

• Lines of force are somewhat like a bar magnet.
• Its origin and maintenance comes from dynamo
  activity in the core
• Circulation of conducting fluid (e.g., molten
  metals) generates magnetic fields.
• So, planetary magnetic fields act like probes of
  unseen planetary interiors

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Earth Dynamo
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Share Question

• The Earth's magnetic dynamo is caused by a
  combination of convection in its molten core and
• a) the Earth's orbit around the Sun
• b) the Earth's rotation
• c) lunar tidal action
• d) the aurora borealis