Volcanoes Lecture Notes

Introduction to Volcanoes

• Characteristics:

  • Iconic pointy mountains.
  • Found in Hawaii, Alaska, and the Pacific Northwest.

• Purpose of Study:

  • Understand different types of volcanoes.
  • Assess eruption violence and potential risks.

Definition of Volcano

• Description:
  • Cone-shaped hill/mountain from magma eruption.
  • Magma forms lava, tephra, and other debris.
• Indicators:
  • Underlying magma source in crust/mantle.
  • Escaping gases driving eruptions.
  • Potential volcanic hazards.
  • Multiple eruptions to build cone.

Distribution of Active Volcanoes

• Types:
  • Shield Volcanoes
  • Composite Volcanoes
• Locations:
  • Shield Volcanoes: Hotspots, oceanic, and continental rifts.
  • Composite Volcanoes: Subduction zones at convergent plate boundaries.

Types of Volcanoes

Shield Volcanoes

• Profile:
  • Low angle, broad triangular landforms.
• Formation:
  • Built by series of lava flows from vents/fissures.
  • Lava is thin and fluid, allowing long-distance travel.
• Example:
  • Mauna Loa, Hawaii: >100 km across, >9 km from ocean floor.

Composite Volcanoes

• Profile:
  • Steep triangular.
• Eruptions:
  • More violent than shield volcanoes.
  • Produce tephra and viscous lava.
• Characteristics:
  • Silica-rich magma, leading to more viscous lava.
  • Eruptions separated by long periods.

Comparison of Volcano Sizes

• Large Volcanoes:
  • Shield and Composite volcanoes.
  • Width: Tens of kilometers.
  • Height: Thousands of meters.
• Smaller Volcanoes:
  • Cinder cones and lava domes.
  • Height: Hundreds of meters.
• Identification:
  • Size comparison with nearby vegetation.

Smaller Volcanoes

Cinder Cones

• Formation:
  • From single eruption.
  • Composed of smaller tephra particles.
  • Cool as they fall to the ground, forming scoria.

Lava Domes

• Formation:
  • Viscous lava slowly oozes and cools.
  • Forms steep-walled, bulbous domes.
  • Can collapse, causing pyroclastic flows.
• Locations:
  • Often in craters of composite volcanoes.
  • Other environments with high silica magmas.

Visual Identification Activity

• Activity:
  • Classify pictures of volcanoes as shield, composite, cinder cone, or lava dome.
• Participants:
  • Students and Jennifer.

Conclusion

• Learning Objectives:
  • Differentiate between types of volcanoes.
• Self-Assessment:
  • Reflect on confidence in identifying volcano types.