Earthquakes

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Earthquakes Volcanoes
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• Objectives
• Given information on Earthquakes, you will be
  able to describe, in writing a) what an
  earthquake is b) what the elastic rebound
  theory isc) how earthquakes are measuredd)
  how earthquakes are related to plate tectonic
  theory e) hazards associated with earthquakes
  andf) the significance of studying earthquakes.
• Given information on Volcanoes, you will be able
  to describe, in writinga) what a volcano isb)
  what types of volcanoes there arec) how
  volcanoes are measuredd) how volcanoes related
  to plate tectonic theorye) hazards associated
  with volcanoes andf) the significance of
  studying volcanoes

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Earthquakes

• Definition
• An earthquake (also known as a tremor or temblor)
  is the result of a sudden release of energy in
  the Earth's crust that creates seismic waves.

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Earthquakes

• Elastic Rebound Theory

• explanation for how energy is spread during
  earthquakes
• plates/blocks of earth shift on opposite sides
  of a fault
• these are subjected to force (Time 1)
• they accumulate energy (Time 2)
• they slowly deform until their internal strength
  is exceeded
• a sudden movement occurs along the fault
• accumulated energy is released
• rocks snap back to their original undeformed
  shape (Time 3)

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Earthquakes

• Measurement
• 1. Magnitude scalea) measures energy
  releasedb) an earthquake one number higher is
  approximately 30 times more powerful (e.g. a 7.0
  vs. a 6.0) (the scale is logarithmic)d) an
  earthquake one number higher produces
  approximately 10 times more ground shaking e)
  examples Moment Magnitude, Richter

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Earthquakes

• Measurement (cont.)
• 2. Mercalli intensity scalea) measures intensity
  or damage of an earthquakeb) quantifies the
  effects of an earthquake on the Earth's surface,
  humans, objects of nature, and man-made
  structures d) scale ranges from I through XII,
  with I denoting a weak earthquake and XII one
  that causes almost complete destruction e) based
  on the amount of resulting physical damage
  received f) data is gathered from individuals
  who have experienced the quake

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Earthquakes

• Plate Tectonics
• Earthquakes are NOT randomly distributed across
  the globe
• They are concentrated along narrow zones
• Most earthquakes (80 or more) occur along plate
  boundaries
• Interior of plates are mostly earthquake free
• Earthquakes define plate boundaries
• Some also occur at Hot Spots

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Earthquakes

• Hazards
• Ground motion
• Liquefaction
• Landslides mass wasting
• Tsunamis

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Earthquakes

• Significance
• It is important to study earthquakes due to the
  loss of life and damage to property they can
  cause
• Human population continues to grow and many
  cities are cited along plate boundaries
• Education is the key to being prepared for
  earthquakes

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Volcanoes

• DefinitionA volcano is an opening, or rupture,
  in a planet's surface or crust, which allows hot,
  molten rock, ash, and gases to escape from below
  the surface. Volcanic activity involving the
  extrusion of rock tends to form mountains or
  features like mountains over a period of time.

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Volcanoes

• Types
• There are 5 general types of volcanoes
• 1. Caldera volcanoes2. Cone volcanoes3. Lava
  Dome volcanoes4. Shield volcanoes5. Strato
  volcanoes

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Volcanoes

• Types of Eruptions1. Effusive (Hawaii)
• 2. Explosive a) Pyroclastic Flow b) Phreatic
  Eruption c) Plinian Eruption d) Strombolian
  Eruption e) Vulcanian Eruption

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Volcanoes

• Measurement
• The Volcano Explosivity Index (VEI) provides a
  relative measure of the explosiveness of volcanic
  eruptions. The scale is based on
• Volume of products erupted
• eruption cloud height
• qualitative observations

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Volcanoes

• Plate Tectonics
• Volcanoes are NOT randomly distributed across the
  globe
• They are concentrated along narrow zones
• Most volcanoes (80 or more) occur along plate
  boundaries
• Interior of plates are mostly volcanoe free
• Volcanoes help to define plate boundaries
• Volcanoes form Hot Spots

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Volcanoes

• Hazards
• 1. tephra (ash fallout)
• 2. pyroclastic flows (Mt. Unzen, Japan)
• 3. tsunamis (Krakatau)
• 4. mass wasting (landslides)
• 5. lahars (volcanic mudflows)
• 6. lava flows (Hawaii)
• 7. gas emissions (Mammoth Lakes)
• 8. directed blast (Mt. St. Helens)
• 9. pyroclastic surge (less dense than
  pyroclastic flows)

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Volcanoes

• Significance
• It is important to study volcanoes due to the
  loss of life and damage to property they can
  cause
• Human population continues to grow and many
  cities are cited along plate boundaries
• Education is the key to being prepared for
  volcanoes

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Summary

• Earthquakes occur due to the elastic rebound
  theory they are measured using the magnitude
  scale they occur along plate boundaries they
  cause ground motion, tsunamis, mass wasting, and
  liquefaction all of which may cause loss of life
  and damage to property
• Volcanoes occur due to molten rock reaching the
  earths surface they are measured using the VEI
  scale they occur along plate boundaries they
  cause pyroclastic and lava flows, ash fallout,
  lahars, mass wasting, earthquakes, and may cause
  tsunamis, all of which may cause loss of life and
  damage to property