What Plate Tectonics Explains

Back to Plate Tectonics

Table of Contents

  1. Continents Fitting Together
  2. Deep Sea Trenches
  3. Earthquakes
  4. Island Arcs
    1. Aleutian Islands
  5. Mountains
    1. Himalayas
    2. Andes
  6. Oceanic Ridges and Seafloor Spreading
  7. Transform Faults
    1. San Andreas Fault
  8. Volcanoes
Continents Fitting Together
Pangea, Continental Drift, emvc.geol.ucsb.edu/2_infopgs/IP1GTect/aPangeaAnim.html
Deep Sea Trenches
  • britannica.com/science/earthquake-geology
    • “Earthquakes are caused by the sudden release of energy within some limited region of the rocks of the Earth.” 
    • “A tectonic earthquake occurs when strains in rock masses have accumulated to a point where the resulting stresses exceed the strength of the rocks, and sudden fracturing results. The fractures propagate rapidly through the rock, usually tending in the same direction and sometimes extending many kilometers along a local zone of weakness. In 1906, for instance, the San Andreas Fault slipped along a plane 270 miles long. Along this line the ground was displaced horizontally as much as 20 feet.”
A woman stands near the 1906 ground rupture northwest of Olema in Marin County. J. B. Macelwane Archives, Saint Louis University
  • A strike-slip fault is a vertical fracture where blocks move horizontally.
  • A dip-slip fault is an inclined fracture where blocks move vertically.
    • In a normal fault the rock mass above the fault slips down
    • In a reverse fault the rock mass above the fault is forced up
      • A thrust fault is a reverse fault with a dip of 45 degrees or less.
Island Arcs
  • An island arc is long chain of oceanic islands
    • running along converging tectonic plates
    • exhibiting intense volcanic and seismic activity
Aleutian Islands

View Video from the Geological Society of London
Continental Plates Collides


View Video from the Geological Society of London
Oceanic and Continental Plates Collide

The Patagonian Andes, Torres del Paine National Park, Chile.
Oceanic Ridges and Seafloor Spreading

View Video from the Geological Society of London
Mid-Atlantic Ridge

Mid-Atlantic Ridge in Iceland

Transform Faults

A transform fault is a strike-slip fault where two tectonic plates slide past each other. The fault ends abruptly at another plate boundary rather than gradually dying out.

San Andreas Fault
  • britannica.com/place/San-Andreas-Fault
    • “The San Andreas Fault is the transform (strike-slip) boundary between two major plates: the Northern Pacific to the south and west and the North American to the north and east. The Northern Pacific plate is sliding laterally past the North American plate in a northerly direction. The rate of movement has been 4 to 6 cm (1.6 to 2.4 inches) per year since the early 20th century. Parts of the fault line moved as much as 6.4 meters (21 feet) during the 1906 earthquake.”

View Video from the Geological Society of London
San Andeas Fault

  • Subduction Volcanoes
    • Subduction volcanoes form when an oceanic plate is subducted beneath a continental plate.
      • For example, the volcanoes on the western and northern margin of the Pacific Plate: New Zealand, New Guinea, Mariana Islands, Japan.
  • Rift Volcanoes
    • “Rift volcanoes form when magma rises into the gap between diverging plates.” (britannica.com/science/volcano)
      • Most Rift volcanoes are on the ocean floor.
  • Hotspot Volcanoes
    • Hotspot volcanoes form when heat deep in the Earth rises, melts rock in the tectonic plate above, and the resulting magma burns its way to the surface.
      • For example, the Hawaiian volcanoes