Earth Structure, Plate Tectonics and Sources of Energy

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Earth Structure, Plate Tectonics and Sources of
Energy
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Structure of the Earth Interior
The process of forming the Earth was complete by
about 4.5 billion years ago.
Dense elements (especially iron and nickel) sank
to the centre of the Earth, forming the metallic
core.
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Lighter material rose to the surface (forming a
thin, weak, crust).
Initial crust was likely too support plate
tectonics as we know it today.
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The Earths interior
1000 C
4000 C
7000 C
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Pea-soup analogy
Process of heat energy transfer
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mantle convection

• Heat transfer from the core to the
• mantle produces slow convection
• of the mantle material

(in the order of centimetres per year)
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Mantle convection produces lateral forces at the
boundary between the mantle and the crust
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Lateral forces at the crust-mantle boundary push
the crust around in different directions and
this leads to the motion of crustal plates. The
plates are moving at rates of cm/year
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14 major plates of Earths crust Scotia plate
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Plate motions
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Transform boundary
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Source http//visearth.ucsd.edu/VisE_Int/aralsea/
bigone.html
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Divergent boundary
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The Plate Tectonics Model
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Convergent boundary
Subduction
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Plates around North America
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(Source U.S. Geological Survey).
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Why Does Plate Tectonics Occur?
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Energy

• Energy can exist in many different forms, and
  comes from a variety of sources.
• Natural disasters occur when there is a sudden
  release of the energy near the surface of the
  Earth.

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Sources of Energy

• Two basic sources
• Solar Energy and Internal Geothermal Energy
• Solar Energy
• Solar Energy drives the water cycle, causing
  evaporation of the oceans and circulation of the
  atmosphere, which allows rain to fall on the land
  and run downhill. Thus solar energy is
  responsible for such natural disasters as severe
  weather, and floods.

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Internal Energy

• only amounts to 0.013 of total energy
  reaching the Earth's surface, but is responsible
  for deformational events mountains, earthquakes
  and volcanism
• Important sources of internal energy
• Radioactive decay

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The Rock Cycle
Energy for the parts of the crustal cycle near
the Earth's surface is solar and gravitational
energy (which control erosion and
weathering). Energy that drives processes beneath
the surface is geothermal and gravitational
energy (which control uplift, subsidence,
melting, and metamorphism).
Source http//www.tulane.edu/sanelson/geol204/st
ructmaterials.htm
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A variety of processes act on and within the
Earth - here we consider those responsible for
Natural Disasters

• Melting - responsible for creating magmas that
  result in volcanism.
• Deformation - responsible for earthquakes,
  volcanism, landslides, subsidence.
• Weathering - responsible for landslides,
  subsidence.
• Erosion - responsible for landslides, subsidence,
  flooding.
• Atmospheric Circulation - responsible for
  hurricanes, tornadoes, flooding.

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• rocks into three major classes
• igneous ( fire),
• sediments (settled particles)
• metamorphic rocks (transformed rocks)
• Within each division there are many groups and
  types

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