Plate Tectonics

• Inner core


  Solid ball of iron/nickel, very hot due to pressure and radioactive decay (contains elements such as uranium that give off heat when they decompose)
• Outer core


  Semi-molten, iron/nickel
• Mantle


  • Mainly solid rock, high in silicon, top layer is semi-molten magma (asthenosphere)
• Asthenosphere


  Semi-molten layer constantly moves due to flows of heat called convection currents, powered by heat from core
• Lithosphere


  • Broken up into plates, majority within mantle, top is the crust
• Crust


  The thin top of the lithosphere, oceanic crust is dense and destroyed by plate movement, continental crust is less dense and not destroyed
• Plate tectonic theory


  Lithosphere is broken up into tectonic plates, plates move due to convection currents in asthenosphere, edges of plates are called plate boundaries
• Different plate boundaries


  • Destructive (plates move towards each other)
  • Constructive (plates move away from each other)
  • Conservative (plates move parallel to each other)
• Destructive plate boundaries


  • Denser oceanic plate subducts below continental, leaves deep ocean trench, fold mountains occur, oceanic crust melted as it subducts, extra magma causes explosive volcanoes
• Constructive plate boundaries


  • Magma rises in gap between separating plates, forms new land, less explosive underwater volcanoes, sea floor spreading
• Conservative plate boundaries


  • Plates move in different directions or at different speeds, no plates destroyed so no landforms created, can cause fault lines and displace water
• Hotspots


  Areas of volcanic activity not related to plate boundaries, hot magma plumes from mantle rise and burn through crust, can create volcanoes and islands
• Paleomagnetism provides evidence for sea floor spreading, as new rock formed at plate boundaries aligns with opposite magnetic polarity to older rock
• Ridge push and slab pull are further forces influencing convergent plate boundaries
• Tectonic plate margins


  Regions where two or more tectonic plates meet
• Tectonic plate margins


  • Exhibit distinct geological activities and landform developments based on the nature of the interactions between the plates
• Primary types of plate margins

  • Convergent Boundaries (Destructive Margins)
  • Divergent Boundaries (Constructive Margins)
  • Transform Boundaries (Conservative Margins)
• Convergent Boundaries (Destructive Margins)


  Two plates move towards each other, typically resulting in one plate subducting beneath the other
• Oceanic-Oceanic Convergence


  • One oceanic plate subducts beneath the other, leading to the formation of deep oceanic trenches and island arcs
• Oceanic-Oceanic Convergence


  • Mariana Trench
  • Japanese island arc
• Oceanic-Continental Convergence


  • Oceanic plate subducts beneath the continental plate, forming volcanic mountain chains along the continental margin
• Oceanic-Continental Convergence


  • Andes Mountains
• Continental-Continental Convergence


  • Neither plate is subducted due to their buoyancy, instead the crust tends to buckle and be pushed upward or sideways, forming high mountain ranges
• Continental-Continental Convergence


  • Himalayas
• Subduction


  The process of one tectonic plate sinking beneath another into the mantle
• Orogeny


  Mountain-building through tectonic plate interactions, including folding, faulting, and uplift
• Divergent Boundaries (Constructive Margins)


  Two tectonic plates move apart from each other
• Oceanic Divergence


  • At mid-ocean ridges, magma from the mantle rises to fill the gap created by the diverging plates, solidifying to form new oceanic crust
• Oceanic Divergence


  • Mid-Atlantic Ridge
• Continental Divergence


  • Divergence within a continental plate can form a rift valley, which may eventually become flooded by seawater, forming a new ocean basin
• Continental Divergence


  • East African Rift
• Seafloor Spreading


  The creation of new oceanic crust at mid-ocean ridges where tectonic plates are pulling apart
• Rifting


  The process of continental plates stretching and breaking apart, often associated with volcanic activity and the creation of new basaltic crust
• Transform Boundaries (Conservative Margins)


  Two plates slide past each other horizontally
• Transform Boundaries


  • San Andreas Fault in California
• Strike-Slip Faulting


  The dominant process at transform boundaries, where movement is predominantly horizontal
• Seismic Activity


  Transform boundaries are often sites of intense seismic activity due to the build-up and release of stress as the plates grind past each other
• Each type of plate margin has distinct characteristics and is associated with specific geological features and processes that dramatically shape the Earth's surface
• Plate boundaries are fundamental to understanding plate tectonics and crucial for assessing geological hazards and resource distribution