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O-Level Earthquakes and Volcanoes (Topic 4.2)

their magnitude, measurement, distribution and impacts

What the syllabus expects

• Earthquakes occur tectonically when stress builds until it exceeds the fault's strength, releasing seismic waves suddenly that radiate energy out from the focus.
  Scope: How tectonic processes affect earthquake magnitude
• An earthquake's magnitude reflects the energy released through ground movement and is recorded with seismometers.
  Scope: How tectonic processes affect earthquake magnitude
• The Richter scale gauges an earthquake's local magnitude, while the Moment Magnitude scale gives more reliable readings for larger earthquakes.
  Scope: How tectonic processes affect earthquake magnitude
• Volcanic eruptions occur tectonically because magma carrying dissolved gases is less dense and pushes upward, breaking through weak spots in Earth's crust.
  Scope: How tectonic processes determine the scale of volcanic eruptions
• Eruption magnitude depends on the quantity of dissolved gases and magma viscosity, so stratovolcanoes erupt violently while shield volcanoes release magma gently.
  Scope: How tectonic processes determine the scale of volcanic eruptions
• The Volcanic Explosivity Index rates the relative explosivity of historic eruptions, weighing the volume of ejected material, the height of the eruption cloud and how long the eruption lasted.
  Scope: How tectonic processes determine the scale of volcanic eruptions
• Earthquakes occur along every plate boundary, concentrated most heavily at the Pacific Ring of Fire.
  Scope: How the distribution of earthquakes and volcanoes shapes where tectonic hazards occur
• Volcanoes lie mainly near convergent and divergent boundaries, while hot spot volcanoes are found away from boundaries.
  Scope: How the distribution of earthquakes and volcanoes shapes where tectonic hazards occur
• Most tectonic hazards sit near plate boundaries and close to earthquakes and volcanoes, though tsunamis and volcanic ash can travel well beyond their geographic region.
  Scope: How the distribution of earthquakes and volcanoes shapes where tectonic hazards occur
• Earthquake hazards such as ground shaking, soil liquefaction, landslides and tsunamis can wreck ecosystems, property and infrastructure, disrupt services and cause injury and death.
  Scope: How tectonic hazards may affect natural and human systems
• Volcanic hazards such as volcanic landslides, lahars, pyroclastic flows, lava flows, volcanic gases and tephra can destroy ecosystems, property and infrastructure, disrupt services and threaten public health and life.
  Scope: How tectonic hazards may affect natural and human systems
• There are benefits too: weathered volcanic material yields fertile farming soil and valuable minerals and building materials, and living near volcanoes allows geothermal energy use and tourism.
  Scope: How tectonic hazards may affect natural and human systems

How it's examined

About 4% of the past-paper style questions in Rae's bank for this subject sit in this topic.

More O-Level Geography topics

Thinking Geographically (Topic 1.1) · Sustainable Development (Topic 1.2) · Geographical Methods (Topic 1.3) · Tourism Activity (Topic 2.1) · Tourism Development (Topic 2.2) · Sustainable Tourism Development (Topic 2.3) · all of O-Level Geography