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Volcanoes

Volcanoes. Get Ready for an ERUPTION!!!. What is a volcano?. A weak spot in the crust where molten material, or magma, comes to the surface Magma- molten mixture of rock-forming substances, gases & water from the mantle Lava- Magma that reaches the surface. Where are volcanoes located?.

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Volcanoes

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  1. Volcanoes Get Ready for an ERUPTION!!!

  2. What is a volcano? • A weak spot in the crust where molten material, or magma, comes to the surface • Magma- molten mixture of rock-forming substances, gases & water from the mantle • Lava- Magma that reaches the surface

  3. Where are volcanoes located? • Volcanoes can be found: • Diverging Plate boundaries (mid-ocean ridge) • Converging plates with subduction zones • Oceanic plate vs. oceanic plate • Oceanic plate vs. continental plate • Hot spots • Area where magma from deep within the mantle melts through the crust like a blow torch • Example: Hawaiian Islands

  4. What is the Ring of Fire? • A circular pattern located around the pacific ocean along the plate boundaries where volcanoes are more common

  5. Results of Volcanoes • Are constructive: • add new rock to existing land • form new islands • Can be destructive • explosive eruptions changes the landscape of and around the volcano

  6. Eruptions • Why do volcanoes erupt? • Less dense magma seeps upward through cracks and creates volcanoes • Gas in the magma is trapped and builds pressure • Closer it gets to surface the less pressure it has and the gases separate (bubbles) • Gases dissolve on the surface and magma is carried out

  7. Types of Eruptions • determined by amount of silica (material made from the elements oxygen and silicon) • 2 types: • Quiet • Lava moves steadily and easily • Explosive • Thick, sticky lava plugs vent like a cork and builds up pressure • Explodes and releases pyroclastic flow • Volcanic ash: fine, rock particles • Cinders: pebble sized particles • Bombs: baseball to car sized particles

  8. Types of Rocks Produced • Type of lava produces different types of rocks • High silica lava: thicker, sticky, lighter colored • Rhyolite • Pumice • obsidian • Low silica lava: flows readily, dark colored • basalt

  9. Stages of a Volcano • Active: (live) erupting or has shown signs that it may erupt In the near future • Dormant: (Sleeping) is not currently erupting but may/can erupt in the future • Extinct: (dead) unlikely to erupt again

  10. Other Volcanic Activity • Hot springs • Groundwater is heated by near by magma rising to the surface and collects in natural pools

  11. Other Volcanic Activity • Geyser • Rising hot water and steam that gets trapped underground and builds pressure until it sprays to the surface

  12. Land Formations from Lava & Ash • Shield Volcano • Created by hot spots • Gently sloping • Cinder Volcano • Steep • Cone-shaped hill/mountain • Composite Volcano • Tall, cone-shaped mountain • Alternating layers of ash and lava

  13. Land Formations from Lava & Ash • Lava Plateaus • Lava moves far from the volcano before cooling which forms high plateaus • Calderas • Huge hole left by the collapse of a volcanic mountain • All magma has been emptied leaving a hollow shell that collapses

  14. Land Formations from Magma • Volcanic Neck: magma hardens in the volcanoes pipes and the soft rock wears away • Dike: magma that was forced across rock layers hardens and the soft rock wears away • Sill: magma that squeezed between rock layers hardens and the soft rock wears away

  15. Land Formations from Magma • Batholith • Mass of rock formed when a large body of magma cools in the crust • Dome Mountains • Rising magma is blocked by horizontal rock layers and forces the rock layers to bend upward into a dome shape and then the soft rock wears away

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