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Earth Science Notes Volcanic Eruptions

Learn about the factors that influence volcanic eruptions and the different features of volcanic activity. Understand the destructive nature of volcanoes and explore the characteristics of intrusive igneous rocks. Discover how trapped gases, silica content, and viscosity impact the explosiveness or quietness of eruptions. Explore different types of volcanic eruptions and their intensity. Witness the devastating effects of volcanic eruptions throughout history. Gain insights into limnic eruptions and their unique elements. Explore various volcanic features such as batholiths, volcanic necks, dikes, sills, and calderas. Discover the circle of life shaped by volcanic activity. 8 Relevant

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Earth Science Notes Volcanic Eruptions

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  1. Earth Science NotesVolcanic Eruptions

  2. Our Objectives Today are… I can … • Explain the Factors that affect Volcanic Eruptions • Describe the Features of Volcanic Activity • Intrusive Igneous Rocks (CH 5) • Describe the destructiveness of Volcanoes • The Circle of Life

  3. Factors Affecting Eruptions Trapped Gases • Carbon dioxide and water vapor get trapped in magma and escape when pressure decreases • Gases that build up a lot of pressure cause explosive eruptions

  4. Factors Affecting Eruptions • Gases build up more pressure in thicker (more viscous) magma. • What type of magma would cause the greatest explosion. Recall: Unit 3 Viscosity means RESISTANCE TO FLOW

  5. Factors Affecting Eruptions Silica Content • Silica is a compound composed of silicon and oxygen • Magma that is silica-rich (i.e. Granitic) produces explosive eruptions • Has a high viscosity (THICK) • TRAPS more gasses • RECALL: silica-rich magma formed granitic (felsic) rocks

  6. Factors Affecting Eruptions Silica Content • Silica is a compound composed of silicon and oxygen • Magma that is silica-poor (i.e. Basaltic) produces quiet explosions • Has a LOW viscosity (Thin) • Forms nonexplosive eruptions • RECALL: silica-poor magma formed basaltic (mafic) rocks Hawaiian Volcano

  7. Basaltic  Andesitic  Granitic (Rhyolitic)

  8. Factors Affecting Eruptions • Low Viscosity (Basaltic) Magma • https://www.youtube.com/watch?v=qTTLYx4Xo2k • Higher Viscosity (Granitic) Magma • https://www.youtube.com/watch?v=e4PUOBIwEv0

  9. Volcanic Eruption Types • Volcanic eruptions are characterized by expolosivity and height of plume. Please Note: as with classification scheme, there are several forms and eruptions may be difficult to distinguish at times

  10. Volcanic Eruption Types Four Main categories of volcanic eruptions (see EN: Kinds of Eruptions) • Hawaiian • weakest • Strombolian • weak • Vulcanian • kind of explosive • Pelean • massive explosions

  11. Volcanic Eruption Types Hawaiian Eruptions https://www.youtube.com/watch?v=CSu_netRm8E

  12. Volcanic Eruption Types Strombolian Eruptions https://www.youtube.com/watch?v=w-S57sd7j9Y

  13. Volcanic Eruption Types Vulcanian Eruptions https://www.youtube.com/watch?v=YF7ib5ToVs4

  14. Volcanic Eruption Types • Pelean Eruptions

  15. Volcanic Eruption Types • Even Larger than a Pelean Eruption are Plinian Eruptions https://www.youtube.com/watch?v=IETUa_nOk1g

  16. Volcanoes Destructiveness Mount Vesuvius - 79 AD

  17. Volcanoes Destructiveness • Mount St. Helen - Washington

  18. Volcanoes Destructiveness

  19. Features Of Volcanic ActivityLimnic Eruptions: Lake Nyos

  20. Features Of Volcanic ActivityLimnic Eruptions: Lake Nyos • Lake Nyos is a deep lake high on the flank of an inactive volcano in Cameroon. • A pocket of magma lies beneath the lake, charging the water with an estimated 90 million tonnes of carbon dioxide (CO2). • In 1986, a limnic eruption at Lake Nyos triggered the sudden release of about 1.6 million tonnes of CO2 that rushed down nearby valleys, displacing all the air and suffocating approximately 1,700 people within 20 km of the lake.

  21. Features Of Volcanic ActivityLimnic Eruptions: Lake Nyos Elements for a Limnic Eruption • Very deep volcanic lake. • Lake has to be over a slow source of volcanic gas. • Lake has to be very, very still.

  22. Features Of Volcanic ActivityLimnic Eruptions: Lake Nyos

  23. Volcanoes Destructiveness

  24. Volcanoes Destructiveness A super-eruption has the potential to cover the United States in 3 feet of ash from a plume. Pyroclastic flow would engulf the greater part of three states, and there is evidence that the last major 'super' eruption plunged the world into a freezing, volcanic winter that lasted a decade. An eruption would devastate world agriculture, severely effect the distribution of food and cause mass famine. This Diagram shows range of potential destruction

  25. After the Aftermath

  26. Features Of Volcanic Activity • Batholiths – formed when magma cools underground

  27. Features Of Volcanic Activity • Volcanic Neck – magma inside volcano cools and outside is eroded away

  28. Features Of Volcanic Activity • Dike – magma that cools in vertical cracks

  29. Features Of Volcanic Activity • Sill – magma that cools in horizontal cracks

  30. Features Of Volcanic Activity • Caldera – top of volcano collapses on emptied magma chamber Photograph by M. Williams, National Park Service, 1977

  31. Features Of Volcanic Activity

  32. Features Of Volcanic Activity

  33. Our Objectives Today were… Can I … • Explain the Factors that affect Volcanic Eruptions • Describe the Features of Volcanic Activity • Intrusive Igneous Rocks (CH 5) • Describe the destructiveness of Volcanoes • The Circle of Life

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