Tectonic Hazards

• The Earth is composed of four main layers: Inner core, Outer core, Mantle, Crust
• Crust


  • Oceanic crust is thinner (5-10km) but heavier and denser
  • Continental crust is thicker (25-90km) but is older and lighter
  • Oceanic crust is continually being created and destroyed as a result of plate movement, where it is denser and so subducts under the continental crust
• Tectonic plates


  The crust is broken into a number of tectonic plates that move on top of the semi-molten mantle below
• Plate boundary or margin


  Where two plates meet
• Earthquakes occur at all types of plate boundaries, with most (approximately 90%) occurring along the Pacific 'Ring of Fire'
• Most volcanoes (approximately 75%) are located around the rim of the Pacific Ocean called the 'Ring of Fire'
• Hotspots occur away from plate boundaries and are plumes/columns of magma which escape through the Earth's crust
• There are many active volcanoes around the edge of the Pacific Ocean
• Types of plate boundary

  • Constructive - plates are moving apart
  • Destructive - denser, heavier oceanic plate subducts under the lighter, less dense continental plate
  • Conservative (transform) - plates move passed each other in opposite directions or in the same direction at different speeds
• Earthquakes are the only hazard at conservative (transform) plate boundaries
• Primary Hazards of Tectonic Activity

  • Volcanic Eruption: Ash, Pyroclastic flow, Lava flow, Gas emissions, Volcanic bombs
  • Earthquake: Ground shaking, Gas emissions
• Secondary Hazards of Tectonic Activity

  • Volcanic Eruption: Lahars, Acidification, Landslides, Climate change, Fires, Floods
  • Earthquake: Building collapse, Landslides, Gas leaks, Fires, Soil liquefaction, Subsidence, Mudflows, Tsunami