OUR HOME PLANET, EARTH

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OUR HOME PLANET, EARTH

• Our Earth is about average among the planets in
  the Solar System, in many respects
• Earth is the largest and most massive of the four
  terrestrial planets, but smaller and less massive
  than the four giant, or Jovian, planets.
• Earth is third in distance from the Sun among the
  four terrestrial planets.
• Earth has a moderately dense atmosphere 90 times
  less dense than that of Venus but 100 times
  denser than that of Mars.
• Earth is also unique in many respects
• Earth is the only planet with liquid water on its
  surface.
• Earths atmosphere is the only one having a
  significant (21) proportion of molecular oxygen.
• Earth is, to our best current knowledge, the only
  planet in the solar system having living
  organisms.
• Earth is the only terrestrial planet having a
  moderately strong magnetic field.
• Earth is the only terrestrial planet having a
  large satellite.

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THE SOLID EARTH

• The field of geology is concerned with the study
  of the structure, history, and activity of the
  solid Earth, including its interactions with the
  atmosphere, hydrosphere, cryosphere, and
  biosphere.
• The structure of the body of the solid Earth
  contains four major zones the core (which is
  divided into inner and outer zones), the (upper
  and lower) mantle, the asthenosphere, and the
  lithosphere.
• The structure of the outer zones is not uniform
  and fixed over the surface of the Earth, but
  shows much variability with position and time.
• The field of plate tectonics deals with this
  spatial and temporal variability.
• Geological phenomena such as earthquakes,
  volcanoes, and continental drift are accounted
  for by plate tectonics.

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Internal Structure of the Solid Earth
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Stanley, 1989, p. 14
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Press Siever, 1982, p. 117
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PLATE TECTONICS IN EARTH SCIENCE

• The theory of Plate Tectonics, which was not
  generally accepted until the mid-20th Century,
  explains a great many features of Earths current
  activity and past history which were previously
  seemingly unrelated.
• Several lines of evidence indicate that the
  continents as they now exist have moved large
  distances over the last few hundred million
  years, both relative to each other and relative
  to the north and south poles of Earths rotation
  axis.
• According to Plate Tectonics, Earths lithosphere
  is made up of individual plates which float on
  a semi-molten asthenosphere.

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PLATE TECTONICS IN EARTH SCIENCE

• The motions of the lithospheric plates are driven
  by convection currents in the asthenosphere.
• The mid-Atlantic rift zone, which includes the
  volcanic island of Iceland, is a region of
  upwelling of molten rock from the asthenosphere,
  which also results in a widening separation of
  the Americas from Europe and Africa.
• When tectonic plates collide with each other, one
  may be subducted beneath the other, or the two
  may merge.
• Plate tectonics also explains other Earth
  activity, such as volcanoes, earthquakes, and
  orogenisis (mountain building).

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Stanley, 1989, p. 166
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Press Siever, 1984, p. 446
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Diagram of Lithospheric Plates and Their
Interactions
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VOLCANIC ACTIVITY

• Volcanic activity, the production of molten rock
  (lava) and its eruption to Earths surface (on
  land or in the oceans) is one manifestation of
  tectonic activity.
• Molten rock is produced as a result of the
  following two major types of plate motion
• Separation (moving apart) of two crustal plates,
  which allows molten rock to rise to the surface
  between them.
• Collision of two crustal plates, with one moving
  beneath the other (subduction), resulting in the
  creation of molten rock from surface materials on
  the subducted plate.
• Volcanic activity in Iceland and elsewhere in the
  mid-Atlantic is due to crustal spreading (the
  mid-Atlantic rift).
• Volcanic activity near the west coasts of North
  and South America is due to subduction of Pacific
  Ocean plates beneath the west edges of the
  continents.
• Some volcanic activity, such as in the Hawaiian
  Islands, is not directly the result of plate
  motions.

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Volcanic Activity due to Plate Spreading
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Volcanic Activity due to Plate Subduction
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Structure of a Volcano
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Volcanoes of the U.S. Pacific Coast
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Stages of Eruption of Mt. St. Helens, 1980
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Eruption of Mt. St. Helens Volcano, May 1980
Post-Eruption View from LandSat
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View of the Volcano Anak Krakatau, in the Sunda
Strait, Indian Ocean, Indonesia Taken by the
Ikonos Satellite, June 11, 2005
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EARTHQUAKES

• Earthquakes are due to sudden motions of crustal
  plates, as a result of fracture or slipping of
  one plate relative to another.
• Zones of high probability of earthquakes (seismic
  activity) are, like volcanic activity, usually
  near plate boundaries or subduction zones.
• The shaking motion of earthquakes is due to the
  propagation of two types of seismic waves
  longitudinal waves, and transverse waves.
• Longitudinal waves, like sound waves, can
  propagate through solids and liquids.
• Transverse waves can propagate only through
  solids.
• Monitoring of seismic waves at large distances
  from earthquake centers have revealed details of
  Earths inner structure, including the fact that
  the outer core is molten (does not transmit
  transverse seismic waves).

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Press Siever, 1984, p. 402
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Earthquake Resulting from Transform Fault Slippage
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Epicenter
Focus
Fault
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Press Siever, 1984, p. 400
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Press Siever, 1984, p. 398
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Anchorage, Alaska Earthquake - Good Friday, 1964
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Loma Prieta (California) Earthquake, 1989
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Production of Tsunami Waves by Earthquakes
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December 26, 2004 Earthquake-Generated Tsunami
(Red Wave Heights Measured by Jason 1
Satellite)
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Longitudinal Waves
Transverse Waves
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Propagation of Seismic Waves Through Earths
Interior
Longitudinal waves travel through both solids and
liquids.
Transverse waves travel through solids only.
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CONTINENTAL DRIFT

• Another aspect of the theory of plate tectonics,
  is that it indicates that the continents of
  Earths crust move (relative to the main body of
  Earth) and change shape with time.
• This explains the similarity of extinct animal
  and plant fossils on adjacent continents (such as
  South America and Africa) which are now separated
  by large bodies of water.
• Magnetized minerals and their orientations
  relative to Earths magnetic poles also provide
  evidence for continental drift.
• Some continental areas now close to the equator
  give evidence of at one time being covered with
  glaciers (which would have required them to be
  closer to the poles).
• This continental drift is also consistent with
  the currently observed plate motions which give
  rise to volcanic and seismic activity.

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Fossils of now-extinct animal species in land
areas now separated by oceans provide evidence of
continental drift.
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Earths Land and Oceans 200 Million Years Ago
Pangaea
Tethys Sea
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200 Million Years Ago
50 Million Years Ago
150 Million Years Ago
100 Million Years Ago
Present
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Zones on Present-Day Continents with Evidence of
Glaciation from Pangaean Times
300 M years ago
Present
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Mountain Building Processes
Press Siever 1984, p. 498
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Space-Based Remote Sensing of the Solid Earth

• Observing the solid Earth from space has many
  unique advantages in comparison to ground- and
  aircraft-based measurements.
• In particular, satellites in appropriate orbits
  can make observations of the entire Earth, at
  repeated intervals and/or over long periods of
  time, using a variety of instrumentation and
  observing techniques.
• The first major satellite program dedicated to
  solid Earth observations was the LandSat series,
  beginning in the mid-1960s.
• The most recent, and most capable, mission of
  this type is the currently operational Terra
  satellite, launched in February, 2000.
• Terra is the first of three major Earth science
  satellites, constituting NASAs Earth Observing
  System (EOS).
• More recently launched sister satellites, in this
  three-satellite series, are the Aqua satellite
  (for studies of Earths oceans and other water
  bodies) and the Aura satellite (for studies of
  Earths atmosphere from above).

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The Terra Earth Observing Satellite Mission

• The Terra mission (EOS-1) was launched February
  24, 2000.
• The primary scientific objectives of the Terra
  mission include studies of the following
• What are Aerosols?
• Changing Global Cloudiness
• Why Isnt Earth Hot as an Oven?
• Changing Global Land Surface

• The Scientific Instruments on Terra are the
  following
• - Advanced Spaceborne Thermal Emission and
  Reflection Radiometer (ASTER)
• - Clouds and Earths Radiant Energy System
  (CERES)
• - Multi-angle Imaging Spectroradiometer (MISR)
• - Moderate-resolution Imaging Spectroradiometer
  (MODIS)
• - Measurements of Pollution in the Troposphere
  (MOPITT)