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Volcanoes

Volcanoes. A volcano is the volcanic mountain, or cone, that forms from the materials that collect around the vent Most volcanoes occur along diverging plate boundaries such as the mid-ocean ridge, or in subduction zones, around edges of oceans Magma : molten rock inside Earth

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Volcanoes

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  1. Volcanoes

  2. A volcano is the volcanic mountain, or cone, that forms from the materials that collect around the vent • Most volcanoes occur along diverging plate boundaries such as the mid-ocean ridge, or in subduction zones, around edges of oceans • Magma: molten rock inside Earth • Lava: magma that reaches Earth’s surface

  3. Vent: the opening that lava flows through • Along with dust, ash, and rock particles

  4. A pipe is a long tube in the ground that connects the magma chamber to the earth’s surface • A lava flowis the area covered by lava as it pours out of a vent

  5. Crater: pit at the top of a volcanic cone • Forms as material is blown out of the volcano’s vent • Example: Mt. St. Helens

  6. Caldera: large hole that forms when the roof of a magma dome collapses • Example: Crater Lake, Oregon

  7. Types of Volcanic Eruptions • The silica content of magma helps to determine whether the volcanic eruption is quiet or explosive • Silica is the material formed from the elements silicon and oxygen

  8. Silica is one of the most abundant materials in Earth’s crust and mantle • The more silica that magma contains, the thicker it is

  9. Quiet Eruptions • Magma flows easily; the gas dissolved in the magma bubbles out gently • Examples: –Hawaii –Iceland

  10. Quiet Eruptions Produce 2 Types of Lava 1. Pahoehoe- fast moving, hot lava; • Surface looks like a solid mass of wrinkles, billows, and rope-like coil 2. Aa- cooler, slower-moving lava; when hardens, forms a rough surface consisting of jagged lava chunks

  11. Explosive Eruptions • Magma is thick and sticky • Magma slowly builds up in the volcanoes’ pipe • Dissolved gases cannot escape • Trapped gases build up pressure until they explode • A pyroclastic flow occurs when an explosive eruption hurls out ash, cinder, bombs, and gases

  12. Stages of a Volcano • Active - is erupting, or has shown signs that it may erupt in the near future • Dormant- does not show signs of erupting in the near future • Extinct- unlikely to erupt

  13. Types of Volcanoes • Shield Volcano • Built from thin layers of lava out of a vent & harden on top of previous layers • Non-explosive eruptions • Not very steep, but can be big • Ex. Hawaiian Islands

  14. Types of Volcanoes • Cinder Cone Volcano • Form when cinders from a vent, pile up around the vent, forming a steep-cone shaped mountain • Moderately explosive, short eruptions

  15. Types of Volcanoes • Composite Volcano • Most common type • Explosive eruptions and lava flow • Layers of lava alternate with layers of ash, cinders, and bombs

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