Tectonic Hazards - Distribution of Hazards & How They Form:

  • Earthquakes and Volcanoes occur mainly at the boundaries at the below plates.
  • Boundaries are active where pressure builds up or lava escapes
  • Most epicentres are on the pacific plate/ring of fire.
  • Earthquakes are at ALL boundaries
  • Biggest Earthquakes are at the convergent, collision and transform margins
  • Volcanoes mainly at convergent and divergent margins
  • 80% of volcanoes at collision margins
  • Tsunamis mainly on the convergent margins or near a coast/ocean
  • Coasts/hotspots can also get hotspots or faults.
Plate Boundaries
 Movement Of Plates And Process
 Geophysical Hazards (frequency and magnitude)
Constructive (Divergent)
 Apart – lava comes out
Volcanoes & Earthquakes
Low Low
Destructive (Convergent)
 Together – one subducts under the other
Volcanoes & Earthquakes
Medium (80%) High
Conservative (Transform)
 Scrape along each other – no lava
ONLY EARTHQUAKES
Medium & High
Collision (Convergent)
Together but both buckle – fold mountains form
ONLY EARTHQUAKES
Medium & Medium


Earthquakes Summary:
  1. Tectonic plates move because of convection currents
  2. Plates stick and pressure builds
  3. Pressure released due to slips and seismic activity is released which leads to an earthquake
  4. Convergent margin builds up pressure which leads to less slips which can lead to a bigger earthquake.
Volcanoes Summary:
  1. Volcanoes occur whenever magma reaches the earth’s surface through a crack
  2. They occur at a divergent, convergent and hotspots
  3. Magma rises through the cracks
  4. An eruption occurs
  5. Convergent gets magma from the melting subducting plate
  6. Hotspot lava from the mantle
Combined Plate Boundaries (Mid-Atlantic Ridge):
  • Divergent margin down the middle
  • Convergent Caribbean margin on the left.
Continental Boundaries (Sans Andreas Fault):
  • The transform boundary in California, USA where plates scrape alongside each other (moving in different direction so friction builds up until it is released as seismic waves)
Intra-Plate Earthquakes:
  • Faults occur away from the plate margins. They account for the smaller, lower magnitude earthquakes
  • Faults are cracks in the earth due to tectonic movement
  • Occur due to tensional forces in the plates. When pressure is released, energy turns into seismic waves
  • An example is the Coniston Fault, The Lake District
Hotspot – Intraplate Volcanoes:
  • Occur due to the upwelling of hot “mantle pumples” under the Earth’s crust
  • Around 70 hotspots worldwide
  • They don’t have to be at plate boundaries, volcanoes are at intraplate.
  • Magma pushes through cracks by thermal erosion (melting in the crust)
  • Finally, the volcano will erupt!
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