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7.4 Volcanic landforms

7.4 Volcanic landforms. Key concepts: What landforms to lava and ash create? How does magma that hardens beneath the surface create landforms? What other distinctive features occur in volcanic areas?

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7.4 Volcanic landforms

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  1. 7.4 Volcanic landforms • Key concepts: What landforms to lava and ash create? How does magma that hardens beneath the surface create landforms? What other distinctive features occur in volcanic areas? • Key terms: shield volcano, cinder cone, composite volcano, caldera, volcanic neck, dike, sill, batholith, geothermal activity, geyser

  2. Landforms from lava and ash • Volcanic eruptions create landforms made of lava, ash, and other materials. These landforms include:

  3. Shield volcanoes • Shield volcano – when thin layers of lava pour out of a vent and harden on top of previous layers to build a wide, gently sloping mountain

  4. Cinder cone volcano • Ash, cinders, and bombs build to form a steep, cone-shaped hill or small mountain called a cinder cone.

  5. Composite volcano • Tall, cone-shaped mountains in which layers of lava alternate with layers of ash

  6. Lava Plateaus • First, lava flows out of several long cracks in the area. It travels far out and cools. After millions of years, the layers can form high plateaus.

  7. Calderas • Caldera – huge hole left by the collapse of a volcano.

  8. Soils from lava and ash • Makes fertile soil because of potassium, phosphorus, etc

  9. Landforms from magma • Features formed by magma include:

  10. Volcanic necks • Forms when magma hardens in a volcano’s pipe

  11. Dikes and sills and batholiths and dome mountains oh my • Dike – magma that forces itself across rock layers and hardens • Sill – magma squeezes between horizontal layers of rock • Batholith – mass of rock formed when a large body of magma cools inside the crust • Dome mountain - Forms when uplift pushes a batholith or a smaller body of magma to the surface

  12. Geothermal activity • Magma a few km below heats underground water • Hot springs and geysers are types of geothermal activity in areas of active volcanoes

  13. Hot springs, geysers • Hot springs – groundwater is heated, hot water rises. May contain dissolved gases or minerals • Geysers – fountains of water and steam that erupt from the ground

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