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Volcanic activity

Volcanic activity. Pg. 89. Magma. Temperature beneath the lithosphere causes rock to melt As pressure increases, the melting point of rock increases At any pressure, a wet rock will melt at a lower temp. Types of magma.

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Volcanic activity

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  1. Volcanic activity Pg. 89

  2. Magma Temperature beneath the lithosphere causes rock to melt As pressure increases, the melting point of rock increases At any pressure, a wet rock will melt at a lower temp

  3. Types of magma Magma formed from the 3 major types of igneous rock- basalt, andesite, and granite Major types of magma: basaltic, andesitic, and rhyolitic Hawaiian volcanoes- basaltic Mt. St. Helens in Washington are andesitic Dormant volcanoes in Yellowstone are rhyolitic

  4. Magma composition • The viscosity of magma is based on silica content more silica, higher viscosity • Basaltic magma • Volcanoes erupt quietly • About 50% silica • Made from rocks in the upper mantle • Oceanic and continental crust • Andesitic magma • found along subduction zones • Made from oceanic crust and sediments • 60% silica, eruptions are in the medium range • Rhyolitic magma • Comes from water rich continental crust • Very explosive • 70% silica content

  5. Basaltic volcano • http://www.youtube.com/watch?v=5hE2DZdl0IA • Andesitic volcano • Rhyolitic volcano

  6. Intrusive activity When magma cools, it forms structures called plutons Plutons are based on size and shape Largest plutons batholiths and stocks; form beneath earths surface; coarse rock Laccoliths mushroom shaped pluton Sills and dikes smallest pluton

  7. Anatomy of a volcano Magma erupts in an opening called a vent Around the vent is a crater Calderas can form when a volcano collapses into the magma chamber

  8. Types of volcanoes • Shield volcano • Mountain w/ broad gently sloping sides that forms when basaltic rock is layered • Cinder cone volcanoes • Forms when material is ejected high in to the air and piles up around a vent • Has steep sides • More explosive • Composite volcanoes • Much larger than cinder cone • Dangerous to humans • Lava alternates with volcanic fragments

  9. Types Shield Cinder cone Composite

  10. Volcanic Material Tephra- rock fragments thrown into the air Can be dust, ash, lapilli, volcanic blocks, or volcanic bombs Rapidly moving volcanic material is called pryoclastic flow

  11. Volcano occurances • Convergent volcanism • At a convergent boundary • Usually form in the sea • Divergent volcanism • Magma forced upward through faults • Causes seafloor spreading

  12. Pg. 90 Create a foldable of the 3 different types of volcanoes. Include a diagram of each on your foldable ( look on pgs. 482-483 for diagrams)

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