Distribution of earthquakes and volcanoes

• An earthquake is a sudden, violent period of groud-shaking. Most occur at the margins of slowly moving tectonic plates.
• Friction and sticking between plates create enormous pressures and stresses which build to breaking point
• The majority of earthquakes are in linear belts that correspond with plate margins

  
• Sparsely distributed earthquakes correspond with constructive plate margins

  
• Denser, broader earthquake zones correspond with destructive plate margins (e.g the 'Pacific Ring of Fire')

  
• Isolated earthquakes occur away from plate margins. Many are triggered by human activities such as mining, oil extraction or resevoir construction

  
• Volcanoes are large, often cone-shaped landforms, formed over long periods by several eruptions
• Volcanoes are fed by molten rock (magma) deep within the Earth's mantle
• Like earthquakes, most volcanoes occur in belts along the plate margins. But someoccur at hot spots where the crust is thin, and magma breaks through the surface (e.g. Hawaiian Islands)