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Volcanoes and Plate Tectonics

Volcanoes and Plate Tectonics. What is a Volcano?. A volcano is a weak spot in the crust where magma comes to the surface. (Notes) So what then is magma?. Magma. Magma is a molten mixture of rock-forming substances, gases, and water that is in the mantle. (Notes)

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Volcanoes and Plate Tectonics

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  1. Volcanoes and Plate Tectonics

  2. What is a Volcano?

  3. A volcano is a weak spot in the crust where magma comes to the surface. (Notes) • So what then is magma?

  4. Magma • Magma is a molten mixture of rock-forming substances, gases, and water that is in the mantle. (Notes) • When magma reaches the surface, it turns into Lava. (Notes) There are two kinds of Magma: • Felsic: have high silica content, are light colored, move slowly (Notes) • Mafic: have low silica content, are dark colored, and flow more easily. (Notes)

  5. Volcano World Website

  6. So where can you find a Volcano? • Volcanoes can be found along plate boundaries, or at a hot spot. (Notes) • The plate boundaries can be either diverging or converging. (Notes) • A hot spot is where magma rises to the surface (crust), and pushes it’s way through it. It doesn’t occur at plate boundaries. (Notes)

  7. Converging plate boundary

  8. Divergent plate boundary

  9. Hot Spots • As the plate moves over the hot spot, a chain of volcanic islands are created in the ocean. This is how the Hawaiian Island chain was created. (Notes)

  10. Volcanic Eruptions • Eruptions can be either quiet or violent. • Quiet eruptions occur when the magma flows easily. The gases that are trapped in the magma leak out gently. There are two kinds of lava that flow easily: (Notes) • A’a lava • Pahoehoe lava (Notes)

  11. Lava

  12. Quiet Eruptions

  13. A’a lava

  14. Pahoehoe lava

  15. Violent Eruptions • Violent eruptions occur when the magma as trapped gases and water in it. • Violent eruptions occur along subduction plate boundaries. • Solid fragments of lava that are thrown from a volcano are called tephra.

  16. Violent Eruptions

  17. Pyroclastic Flow

  18. Lahar

  19. Stages of a volcano • Dormant: a volcano that is not active but could be in the future. • Active: a volcano that is currently erupting • Extinct: a volcano that will not erupt again.

  20. Dormant

  21. Active

  22. Extinct

  23. There are 3 kinds of Volcanoes • Shield Volcano • Cinder cone volcano • Composite volcano

  24. Shield Volcano • Occur on hot spots where layers of lava pile up creating a dome shaped mountain. • Example: Mauna Kea and Mauna Loa

  25. Cinder Cone Volcano • Occur where lava ash is thrown from the volcano and piles up along the sides, creating a cone shaped mountain.

  26. Composite Volcano • Occurs when layers of lava flow alternate with layers of lava ash and pile up, creating a mountain.

  27. Sometimes magma can heat the local groundwater.This creates a hot spring

  28. Magma Landforms When the magma doesn’t erupt, it is left underground to cool and solidify. This creates certain features like: -dikes -sills -volcanic necks -batholiths -lacoliths

  29. Devils Tower, WyomingLocation: 44.6N, 104.7WElevation: 5,112 feet (1,558 m)

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