PLATE BOUNDARIES

• What are the different types of plate boundaries?

  Divergent, convergent, and transform fault boundaries
• What is the movement of lithospheric plates called?

  Tectonic movement
• What does the lithosphere consist of?

  The crust and the upper layer of the mantle
• What causes lithospheric plates to move?

  Convection currents in the Earth’s interior
• What are the characteristics of divergent plate boundaries?

  • Plates separate and move apart
  • Form new lithosphere (young seafloor)
  • Occur at mid-ocean ridges or rifted continental margins
• What happens at convergent plate boundaries?

  • Plates move toward each other
  • Oceanic plate bends downward at subduction zones
  • Can form mountain ranges or deep-sea trenches
• What occurs when two oceanic plates converge?

  The older, denser plate is subducted, forming a volcanic island arc
• How does oceanic-continental convergence differ from continental-continental convergence?

  Oceanic-continental convergence involves subduction, while continental-continental convergence results in mountain building
• What is a subduction zone?

  A region where one tectonic plate is forced under another
• What geological features are commonly formed at convergent boundaries?

  Mountain ranges, deep-sea trenches, and volcanoes
• What is the Mariana Trench known for?

  It is the deepest ocean depth at 11 km below sea level
• What happens to oceanic crust at convergent boundaries?

  It is forced down into the mantle where it begins to melt
• What are the effects of continent-continent collision at convergent boundaries?

  • Produces mountain ranges
  • Compressional forces drive the mountain building process
  • Examples include the Himalayas and the Appalachians
• How were the Himalayas formed?

  Through the collision of the Indo-Australian Plate with the Eurasian Plate
• What is the Benioff Zone?

  It is the area of frequent earthquakes along the top of a descending oceanic plate
• What occurs at divergent plate boundaries?

  • Plates move away from each other
  • Magma rises to create new oceanic crust
  • Commonly associated with mid-ocean ridges and rift valleys
• Who proposed the concept of sea-floor spreading?

  Harry Hess
• What is the process of sea-floor spreading?

  Hot magma rises from the asthenosphere, creating new ocean crust as it cools
• How do divergent boundaries within continents differ from those under the sea?

  Divergent boundaries on land produce rift valleys, while those under the sea create mid-ocean ridges
• What are the characteristics of transform fault boundaries?

  • Plates slide past each other
  • Commonly associated with earthquakes
  • Do not create or destroy lithosphere
• What is created at divergent boundaries when plates pull apart?

  New crustal material sourced from molten magma
• What happens to divergent boundaries that form within continents?


  They eventually open up and become ocean basins
• What is the term for the process at a divergent boundary where two oceanic plates pull apart?

  Sea-floor spreading
• Who proposed the concept of sea-floor spreading and when?

  Harry Hess proposed it in the early 1960s
• What occurs during sea-floor spreading?


  Hot magma rises from the asthenosphere into existing ocean crust through fractures
• What geological feature is formed as magma cools during sea-floor spreading?

  A mid-ocean ridge made of basaltic rock
• What is the world's longest mountain chain and where is it located?

  The Mid-Atlantic Ridge, which is underwater
• How fast does the Mid-Atlantic Ridge spread?

  About 1-2 centimeters per year
• What is an example of a fast-spreading ridge?

  The East Pacific Rise
• What is the characteristic of a transform plate boundary?

  Two plates sliding past each other
• What geological features are created at transform boundaries?

  A linear fault valley or undersea canyon
• What happens to rocks at transform boundaries?

  They are pulverized as the plates grind along
• What is the San Andreas Fault an example of?

  A transform fault
• What type of motion does the West Valley Fault exhibit?

  Right-lateral strike-slip motion
• What is the potential magnitude of earthquakes produced by the West Valley Fault?

  Magnitude of 7 or higher
• What concept did J. Tuzo Wilson introduce regarding volcanic islands?

  The concept of a "stationary hotspot"
• What is the Wilson Cycle?

  A sequence explaining the origin of the Appalachian Mountains
• What are the three basic ways that tectonic plates interact with one another?

  • Convergent boundary: Plates collide
  • Divergent boundary: Plates separate
  • Transform boundary: Plates slide past each other
• What geological features can be found on the deep sea floor?


  Seamounts, guyots, and black smokers
• What is the depth and width of the rift valley created by the Mid-Atlantic Ridge?

  About 1-2 km deep and several kilometers wide