Tectonic Processes and Hazards

• What are the two parts of the crust? 


  Oceanic Crust

  Continental Crust
• Core

  • 6000°C
  • Made of Iron and Nickel
  • 3450km radius
• Mantle

  • Above 2000°C
  • Semi-molten
  • Upper Part of the Mantle is solid
• Crust

  • Outer Crust (Oceanic Crust)- denser- 6-10km
  • Inner Crust (Continental Crust)- Less Dense- 5-40km
• What makes up the Lithosphere? 


  The Oceanic Crust

  The Continental Crust
• Convection currents within the Mantle tear the Crust Apart.

  The Earth is divided into huge rock slabs called plates

  
• Structure of the Earth

  • Inner Core
  • Outer Core
  • Mantle
  • Crust

  A)

  
• The Earth's crust is split into 7 Major Plates and 8 minor plates
• Where plates meet is called a plate margin
• The relative movement and type of crust determines the type of plate margin
• Convection


  Convection Currents affect the Asthenosphere (upper Mantle). This rips apart or forces together slabs of continental crust
• What is the Asthenosphere? 


  The upper mantle
• Slab Pull

  Newly formed Oceanic crust forms mid-ocean ridges. As the crust cools, it becomes more dense and sinks- pulling the plate with it

  
• Ridge Push


  The Oceanic crust formed at constructive (divergent) margins is hotter and less dense. It rises to form Oceanic Ridges. These ridges slide sideways. This pushes the crust causing ridge push.

  
• Subduction 


  Where plates collide, the more dense crust is subducted (dragged under). The less dense (often Continental) goes on top. This is Called crust subduction.

  
• What occurs at Destructive margins? 


  Subduction.
• What occurs at Constructive margins? 


  Ridge Push
• What occurs at Collision Margins? 


  If two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains. This is called a collision margin.

  
• What happens at a conservative margin? 


  At a conservative plate boundary, the plates move past each other or side by side, moving at different speeds. 

  
• Hot Spots 


  Where a magma plume forces through the crust either in an oceanic plate or through continental crust. This creates a chain of volcanic islands as the plate moves. This has led to previous super volcanic eruptions.
• Earthquakes are common on Plate Margins
• Long Narrow belts on the edge of continents and oceans
• Some in the middle of oceans
• Earthquakes often occur in:

  • Japan
  • Pacific ring of Fire
  • Southern Europe/ Asia
  • Mid-ocean ridges
  • Western America
• A- Crust

  B- Epicentre

  C- Fault Line

  D- Focus

  E- Tremors

  
• Focus (hypocentre)


  The Point inside the crust where pressure is released
• Epicentre 


  The point on the surface above the focus
• Seismic Waves 


  Waves that radiate out from the focus like ripples
• How many seismic waves are there?

  3
• What are the three seismic waves?

  Primary waves (P waves)

  Secondary waves (S waves)

  Surface Love waves (L waves)
• Primary waves

  • Travel quickly (give a warning)
  • Unlikely to cause damage
  • Can move through liquids and solids
• Hazard


  A potential threat to human life and property
• Types of natural hazards

  • Hydro-meteorological (caused by climatic processes)
  • Geophysical (caused by land processes)
• • Geophysical hazards

  • Occur near plate boundaries
  • Plates move at different speeds and directions which can cause collisions, earthquakes and volcanic activity
• • Intraplate earthquakes

  • Occur near the middle of plates
  • Caused by pre-existing weaknesses in the plates that become reactivated, forming seismic waves
• • Volcanic hotspots

  • Localised areas of the lithosphere (Earth's crust and upper mantle) which have an unusually high temperature due to the upwelling of hot molten material from the core
• Volcanic hotspots, such as the Ring of Fire, are situated amongst the centre of plates
• • At hotspots, such as the Hawaii hotspot, magma rises as plume (hot rock)
• • The most powerful earthquakes usually occur at convergent or conservative boundaries
• • Belts of tectonic activity

  • OFZ (Oceanic Fracture Zone) - belt of activity through the oceans and along the mid-ocean ridges
  • CFZ (Continental Fracture Zone) - belt of activity along the mountain ranges