Endogenic Processes of Volcanism and Tectonics

• Examples of Endogenic Processes

  • Volcanism
  • Tectonics
• Volcanism effects

  • Subsurface effects of magma:
  • Intrusive igneous bodies
  • Contact metamorphism
  • Hydrothermal springs
  • Surface effects of volcano deposits:
  • Airborne fallout of ash
  • Airborne ballistic scoria
  • Lava eruptions
  • Aa lava – Flows moderately and forms a brittle crust
  • Pahoehoe lava – Flows slowly and has a smooth texture
  • Lava domes are a resulting structure of slow travelling lava, the lava expands in one spot instead of flowing creating a dome
• Volcano Types

  • Cinder/Scoria cones
  • Stratovolcanoes
  • Shield Volcanoes
  • Flood Basalts
• Cinder/Scoria Cones

  ·      Shape is defined by eruptive material, formed by ejected scoria

  ·      Monogenic
• Stratovolcanoes

  ·      Large variation in height – 100 to 1,000s of m

  ·      Polygenic

  ·      Aa lava

  ·      Occur on a much larger timescale and heavily impact the features of the surrounding areas with ash and pyroclastic flows
• Shield Volcanoes

  ·      Polygenic

  ·      Gentle slopes 2-12 degrees

  ·      The sides of the volcano consist of previously erupted material, which build up over time. E.g., Hawaiian island shield volcano
• Flood Basalts

  ·      High volume eruptions that flood vast areas of the Earth, broad regions are covered by flat lying lava

  ·      They are a result of mantle hotspots or divergent boundaries
• Tectonic Events

  • Rift Valleys
  • Mountain Building
  • Uplift
• Rift Valleys

  • When extension of continental crust leads to the formation of a rift zone
  • Over time consistent rifting can contribute to the formation of a new ocean
• Mountain Building

  • A part of the geographical cycle, where landscapes are uplifted, then they meet maturity before experiencing erosional decay where their topography returns to a low elevation. They will then experience uplift again
• Uplift


  • Uplift through underlying materials e.g., trapped salt pushes up against the crust
  • Extensional uplift (mantle upwelling)
  • Isostatic uplift
  • Epeirogeny – the broad region upwarp of cratons, not well understood
  • Collisional/orogenic uplift
• Relationship between Uplift, Topography and Erosion

  • Uplift leads to decreased temperatures -> less vegetation -> increased physical weathering
  • The increase in slope and relief leads to increased erosion -> gravity and mass wasting as well as higher stream power
  • Stronger uplift -> stronger erosion -> stronger reduction in elevation (higher mountains eroded quicker)
  • Negative feedback loop
  • Erosion of valleys can focus exhumation, resulting in rock uplift (through isostatic rebound) along major rivers