Recording-2025-02-10T16:36:00.011Z

Types of Volcanoes and Their Lava

• Volcanic Types and Lava Composition

  • Basalt:

    • Common in oceanic volcanoes (ocean ridges, ocean islands).

    • Non-explosive, produces "friendly" eruptions.

  • Intermediate Lava:

    • Associated with subduction zones.

    • Basalt magma gets contaminated with granitic (granitic chemistry) rocks.

    • Produces Andesite, which is highly explosive.

Hazards of Explosive Volcanism

• Andesite Eruptions:

  • Produces fast-moving pyroclastic flows.

  • Pyroclastic flows can travel down valleys, destroying everything in their path.

• Destructive Effects:

  • Flows consist of hot ash and rock fragments.

  • Capable of burning trees, livestock, and posing threats to human life.

Volcanic Explosivity Index (VEI)

• Communication of Volcano Risks:

  • Mercalli Scale: Measures intensity of earthquakes.

  • Saffir-Simpson Scale: Measures hurricane categories.

  • VEI: Used to predict and communicate a volcano's potential explosiveness.

Shield vs Stratovolcanoes

• Shield Volcano:

  • Characterized by gentle slopes.

  • Comprised mainly of basalt.

  • Example: Hawaiian volcanoes.

• Stratovolcano:

  • Often located above subduction zones.

  • Contains higher silica, resulting in more viscous magma and more explosive eruptions.

  • Examples: Mount Pinatubo in the Philippines, volcanoes in the Andes.

Yellowstone National Park and Volcanism

• Yellowstone Characteristics:

  • Contains a mantle plume similar to Hawaiian hot spots but interacts with continental crust.

  • Produces a variety of volcanic rock types, including basalt and rhyolite.

• Historical Events:

  • Major eruptions produced large calderas.

  • Evidence of volcanism includes boiling mud, geysers, and ash deposits.

Caldera Formation and Monitoring

• Calderas:

  • Formed by large voluminous eruptions leading to the collapse of ground above emptied magma chambers.

  • Long Valley Caldera in California is an example.

• Monitoring Systems:

  • USGS monitors volcanic activity through gas emissions, seismic activity, and ground deformation to predict potential eruptions.

Factors Influencing Explosivity

• Magma Composition:

  • Low viscosity (basalt) = less explosive eruptions.

  • Higher viscosity (rhyolite) = more explosive eruptions.

• Eruption Features:

  • Height of eruption column and amount of ash produced both indicate explosiveness.

Historical Eruptions and Their Impact

• Examples of Eruptions:

  • Mount St. Helens: notable for explosive eruptions.

  • Mount Pinatubo: predicted eruption saved lives and property due to effective monitoring.

• Pyroclastic Flow Characteristics:

  • Particles settle with greatest density at the bottom, creating more solid rock layers.

  • Can produce significant hazards during eruptions.