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Volcanoes

Volcanoes. Chapter 18 Page 498. 18.1 Zones of Volcanism. Volcanism = describes all the processes associated with the discharge of magma, hot fluids and gases. Ring of Fire. Active volcanoes that create a “ring” pattern in the pacific ocean

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Volcanoes

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  1. Volcanoes Chapter 18 Page 498

  2. 18.1 Zones of Volcanism • Volcanism = describes all the processes associated with the discharge of magma, hot fluids and gases.

  3. Ring of Fire • Active volcanoes that create a “ring” pattern in the pacific ocean • Typically volcanoes from convergent and divergent boundaries.

  4. Convergent Volcanoes • Volcanoes that form from plates colliding or subducting. • Land volcanoes tend to be explosive

  5. Divergent Volcanism • 2/3rds of volcanism underwater • The ocean ridges that form tend to release giant pillow lava. • Tend to be non- Explosive and large

  6. Hot Spots • Volcano that forms NOT at a plate boundary. • Magma rises from HOT areas of the mantle

  7. Flood Basalts • From hot spots below the continental crust • Basalt rises up along cracks called FISSURES. • Often leaves a PLATEAU structure behind.

  8. Anatomy of a Volcano • Conduit = tube • Vent = opening • Crater = depression around the vent

  9. Calderas • Large crater that may have formed from a large explosion. • Sometimes forms into a lake

  10. Complete the worksheet on labeling the parts of a volcano

  11. Types of Volcanoes • 1. Shield Volcanoes • 2. Cinder Cones • 3. Composite Volcanoes • All three depend on 2 factors: • Type of material that forms it • Type of eruption

  12. Shield Volcano • Broad, gently sloping, circular base • Largest type • Nonexplosive eruption which leaves layers of lava.

  13. Cinder Cone • Formed from eruptions that eject small pieces of magma from the air. • The small pieces pile back around the vent causing the cinder cone shape. • Small and steep

  14. Composite Volcanoes • Violent eruptions • Formed by layers of hardened chunks of lava from the eruptions alternating between explosions and oozing of lava • Cone shaped with concave slopes (larger than cinder)

  15. 18.2 Explosive Eruptions • Tephra = is the erupted material from the volcano. • Can be solidified lava OR pieces of crust • Classified by size: • Less than 2 mm is called ASH • Largest is called BLOCKS

  16. Explosion effects • Ash can rise into atmosphere hurting: • Airplanes • Change in weather - Block sun’s rays therefore lower temps

  17. Proclastic Flows • Clouds of ash and other tephra • Travels at speeds of 125 mph • Mixed with hot gases • up to temps of 700*C • Can kill thousands AFTER the explosion

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