2.3 Distribution of Earthquakes, Volcanoes, and Tectonic Hazards

How might distribution of earthquakes and volcanoes influence the location of tectonic hazards?

How are earthquakes distributed?

occurs along

• all types of plate boundaries

  • more common at convergent PB at subduction zones

    → more stress is built up during subduction

• largest concentration of earthquakes is at the

  • Pacific Ring of Fire

e.g., 

Broad belt of earthquakes 

• along convergent PB 

  • in the Pacific Ring of Fire

Narrow belt of earthquakes

• along divergent PB 

  • at the Mid-Atlantic Ridge

• along the transform PB 

  • at the San Andreas Fault

• exception

  • there are some isolated earthquakes

    • occurs away from PB

    • such as within the Eurasian Plate

How are volcanoes distributed?

generally located near

• convergent PB

  • e.g., found along subduction zones in the

    • Pacific Ring of Fire

• divergent PB

  • e.g., found between NA and Eurasian plates

  → at these PBs, magma rises to the surface

  • forms volcanoes

• found away from PBs

  • an exception

    → hot spot volcanoes

Volcanoes not found at

• transform PB

• C-C convergent PB

  → cuz at these PBs, magma does not rise to the Earth’s surface

  • no volcanoes formed

How are tectonic hazards distributed? (1/2)

Earthquake Hazards

• ground shaking

• soil liquefaction

• landslides

• tsunamis

distribution

• ground shaking, soil liquefaction, landslides

  • often localised

  • generally located within the same geographical region as the earthquake

• as earthquakes are found along PBs

  • its hazards too are found there

• however tsunamis are not localised

  • may spread beyond the geographical regions

    • travelling far from where the earthquake originated from
      → without great loss of energy

How are tectonic hazards distributed? (2/2)

Volcanic Eruption Hazards

• tephra

• volcanic gases

• lava flows

• pyroclastic flows

• lahars

• volcanic landslides

  • all found around the volcanoes except ‘tephra’

  • volcanoes found along convergent + divergent PB

    → hazards found generally around there too

• however ‘tephra’ is not localised

  • may spread beyond the geographical regions

    • travelling far from where the volcanic eruption originated from