Tectonics, Earthquakes, Volcanism

• Major plates

  • Eurasian plate
  • Pacific plate
  • African plate
  • Antarctic plate
  • Indian plate
  • North American plate
  • Philippine plate
  • Australian plate
  • South American plate
  • Cocos plate
  • Caribbean plate
  • Nazca plate
• Orogeny


  Process of mountain building that takes tens of millions of years, usually producing long linear structures known as orogenic belts
• Two main processes of orogeny


  • Deformation: continental collisions, resulting in folding and thrust-faulting
  • Volcanic Activity
• Other processes of orogeny include metamorphism
• Marine fossils on top of Everest are a clue for mountain formation
• Orogenesis (Mountain Building)


  1. Oceanic-continental plate collision

  2. Oceanic-oceanic plate collision

  3. Continental-continental plate collision
• Folding


  Bending of rock strata that are subjected to compressional forces
• Faulting


  Occurs when rocks on either side of a fracture (break) are displaced relative to the other side
• Factors affecting rock deformation


  • Intensity of applied stress
  • Heat - Temperature of the Rock
  • Amount of Time the Stress is applied
  • Rock Composition
• Types of faults


  • Normal
  • Reverse
  • Strike-Slip
• The movement of tectonic plates causes stress on rock structures
• Stress


  The amount of force per unit area that is placed on an object
• Deformation


  The process by which rocks change shape when under stress
• When rocks bend, folds form; when rocks break, faults form
• Scientists assume that all rock layers start out as horizontal layers deposited on top of each other over time
• Fault plane


  The location where two fault blocks meet

  
• Hanging wall


  The block above the fault plane
• Footwall

  The block below the fault plane
• Strike-slip fault


  The fault blocks move past each other horizontally
• Normal fault


  The hanging wall moves down relative to the footwall
• Reverse fault


  The hanging wall moves up relative to the footwall
• Types of mountains


  • Fold-and-thrust mountains
  • Fault-block mountains
  • Dome mountains
  • Volcanic mountains
• Fold-and-thrust mountains are formed by continent-continent collisions
• Dome mountains are formed by the movement of molten rocks or magma under the Earth's surface
• Volcanic mountains are formed by volcanic activity that pushes the nearby regions upwards
• The Appalachian Mountain System is an example of a fold-and-thrust mountain range
• Earthquake

  The rapid movement of the ground, usually back and forth and up and down in a wave motion, caused by the rapid release of energy as the tectonic plates move
• Focus

  The sub-surface area along a fault plane where motion is initiated
• Epicenter


  The area at the surface directly above the focus
• Aftershock (foreshock)


  Shocks that occur after (before) the main shock
• Moment Magnitude Scale


  A modified version of the Richter scale used to assess earthquakes
• 99% of earthquakes are associated with plate boundaries, and over 500,000 occur worldwide each year
• Volcano


  A place where extremely hot material from inside Earth erupts at the Earth's surface, including gas, ash, lava, and solid volcanic rock
• Most volcanoes are found on or at the edge of tectonic plates because the movement of the plates creates weaknesses in the crust and generates intense heat that can melt rock
• There are around 600 active volcanoes on Earth, with about 50 eruptions occurring per year, and around 70 active volcanoes in North America
• Intrusive volcanic activity


  Magma solidifies below the surface, forming intrusive igneous rocks but no volcanoes
• Extrusive volcanic activity


  Magma is expelled to the surface, forming extrusive igneous rocks and volcanoes
• Two types of volcanoes


  • Shield volcanoes
  • Composite (stratovolcano) volcanoes
• Shield volcanoes have a shield-like, not steep shape, and are formed by effusive eruptions of low viscosity lava that flows away from the vent
• Composite (stratovolcano) volcanoes are steep, cone-like structures formed by explosive eruptions of high viscosity lava and pyroclastic debris that falls close to the vent