Types of Eruptions, Catastrophic Summit Collapse Pt3

Volcanic Explosivity Index (VEI)

  • The VEI is a scale used to measure the explosiveness of volcanic eruptions.

  • Important to understand the relationship between eruption styles and the VEI scale.

Types of Volcanic Eruptions

  1. Hawaiian Eruptions

    • Typically characterized by fluid basaltic lava flows.

    • Low viscosity and effusive in nature.

    • VEI typically ranges from 0 to 1, indicating non-explosive activity.

    • Can create large shield volcanoes due to the long-distance flow of lava.

  2. Strombolian Eruptions

    • Intermediate eruptions that are visually spectacular, resembling fireworks.

    • Characterized by bursts of pyroclastic material and andesitic lava.

    • VEI ranges from 1 to 3, indicating moderate explosiveness.

  3. Plinian Eruptions

    • Characterized by powerful vertical ejection of gases, superheated toxic gases, and pyroclasts.

    • Extremely explosive, resulting in significant ash clouds and debris fallout.

    • VEI typically ranges from 3 to 8, with 8 being the highest.

    • composite/strato

Key Characteristics of Eruptions

  • Pyroclasts: Volcanic rock fragments ejected during explosive eruptions.

  • Composition types in volcanoes include associates of felsic, intermediate, and mafic materials.

  • Plinian eruptions are associated with high viscosity magma and a high gas content.

  • Volcano types based on eruption styles:

    • Stratovolcanoes or Composite volcanoes: Common for Plinian eruptions.

    • Shield volcanoes: Characteristic of Hawaiian eruptions.

    • Cinder cones: Characteristic of Strombolian eruptions.

Historical Eruption Examples

  • Mt. St. Helens: Example of a Plinian eruption with significant ash output.

  • Pinatubo: Notable for its massive eruption that produced 10 times the ash of Mt. St. Helens.

  • Tombora: Even larger eruption with significant historical impact.

  • Yellowstone: Unique case of a volcanic province with significant historical eruptions.

    • Erupts on a scale of hundreds of thousands of years

    • Known for its massive geological structures, such as calderas.

Yellowstone Volcano

  • Yellowstone is not considered a volcanic edifice due to its size; it is classified as a volcanic province.

  • It features a large caldera, approximately 80 kilometers wide, formed from collapse after a massive volcanic eruption.

  • The last significant eruption occurred around 640,000 years ago; it can obliterate large areas and has a recurrence interval of several hundred thousand years.

  • Hotspots like Yellowstone feature geological phenomena different from typical volcanic activity.

  • Composition of rocks in the area includes felsic rhyolites, formed from melting of continental lithosphere, resembling granite.

  • hot spot through a continent

Geothermal Features

  • Yellowstone is known for its geothermal activity, including geysers and hot springs such as Old Faithful, which erupts regularly

  • Hot springs are characterized by varying temperatures and compositions influenced by volcanic activity.

Catastrophic Sub-Summit Collapse

  • Very rare volcanic phenomena characterized by massive eruptions leading to caldera formation.

  • Examples include:

    1. Crater Lake (Oregon): Formed from the collapse of a stratovolcano due to explosive eruptions, such a large eruption it fell into the magma chamber below, 12km across, filled in by water

    2. Krakatoa (Indonesia): Famous for its cataclysmic eruption and subsequent collapse. Anak Krakatau=cinder cone, between Sumatra and Java

    3. Santorini (Greece): Notable historical eruption with lasting geographical impacts. Kameni=cinder cone, controlled by a subduction zone

    4. Hawaii: Mauna Kea tallest volcano in the world, not active, Mauna Loa active + Kilauea= shield volcanoes , determined by viscosity most active, huge magma chamber, lava tunnel (lava wants to go to the ocean), short RI, high frequency fluid eruptions