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Understanding Volcanoes: Types, Viscosity, and Eruptive Behavior

Explore the fascinating world of volcanoes in this comprehensive overview. Learn about magma formation deep within the Earth's crust, the role of temperature and pressure in melting rocks, and how magma's viscosity affects eruption styles. Discover the three main types of magma—basaltic, andesitic, and rhyolitic—and how they contribute to varying eruption characteristics. Gain insights into the anatomy of volcanoes, including different types like shield, cinder-cone, and composite volcanoes, as well as the geologically active hotspots that create them.

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Understanding Volcanoes: Types, Viscosity, and Eruptive Behavior

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Presentation Transcript

  1. Ch. 18 Volcanoes

  2. Viscosity Tepha Vent Hot Spot Caldera Cinder-Cone Volcano Composite Volcano PyroclasticFlow Shield Volcano Crater Ch. 18 Vocabulary

  3. Magma • Proves that earth is geologically active • Magma formed deep within earths surface • Temperatures must be high enough to melt rock - 800-1200 oC • Temperatures increase with depth • Pressure increase with depth • Increase Pressure – Decrease melting point • B/C Magma is less dense than surrounding rock, Magma rises to surface

  4. Magma Composition • Viscosity • Resistance to flow • Hotter the magma, lower the viscosity • Silica content • Determines viscosity • High content – high viscosity • Water content • High amounts of water will evaporate, build pressure • More explosive • Three Types of Magma

  5. Magma Types • Basaltic • Low Viscosity (50% Silica) • Quiet Eruptions • Andesitic • Intermediate Viscosity (60% Silica) • Intermediate Eruptions • Rhyolitic • High Viscosity (70% Silica) • Great Eruptions

  6. Volcano Locations: Ring of Fire

  7. Anatomy of a Volcano • Vent • Magma reaches the surface and lava erupts out of a vent • Lava solidifies and builds up mountain around vent • Cone (1 km wide) or Caldera (50 km wide)

  8. Types of Volcanoes • Shield • Broad gently sloping sides • Layer upon layer of basaltic lava accumulation (non-explosive) • Low viscosity

  9. Types of Volcanoes • Cinder Cone • Material exploded high into the air and comes back to earth • Steep side from explosive eruptions • More viscous lava contains more gases which fuel more explosive eruptions

  10. Types of Volcanoes • Composite • Volcanic fragments and lava eruptions – most common • Contains large amounts of silica, water, and gases • Potentially dangerous to people and environment

  11. Other locations for Volcanoes • Hot Spots • Located away from plate boundaries • High temperature mantle plumes rise towards the surface • Hawaiian Islands

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