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Volcanoes

Volcanoes. Earth Science Day 30 . Bell Ringer. Turn in your corrected test! What are the 3 types of volcanoes? Which one is the most deadly? Which one is the least deadly? . 18.1 Learning Objectives. What is the difference between magma and lava?

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Volcanoes

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  1. Volcanoes Earth Science Day 30

  2. Bell Ringer • Turn in your corrected test! • What are the 3 types of volcanoes? Which one is the most deadly? Which one is the least deadly?

  3. 18.1 Learning Objectives • What is the difference between magma and lava? • Explain what viscosity means and provide examples. • Describe the 3 types of magma and how they determine volcano explosiveness.

  4. What is magma? • Magma: a mixture of molten rock, mineral grains, and gases beneath Earth’s surface • All volcanoes are fueled by magma below them.

  5. When do rocks melt? • Most rocks melt at 800o – 1200o Celsius. • When rocks are WET, they melt more easily (at a lower temperature).

  6. What is viscosity? • Viscosity: resistance to flow • High viscosity—thick (like motor oil, hand soap) • Low viscosity—thin (like water, gasoline)

  7. What is viscosity? • Viscosity depends on… • 1) Temperature • Hot lava = low viscosity (thinner) • Cooler lava = high viscosity (thicker) • 2) Silica content • Little silica = low viscosity (thinner) • Lots of silica = high viscosity (thicker)

  8. What different types of magma exist? • Basaltic magma: made of basalt • Found in Hawaiian volcanoes • Rhyolitic magma: made of granite • Found in Yellowstone National Park

  9. How does viscosity relate to explosiveness? • Basaltic magma • Low viscosity (thin)…not explosive • Rhyolitic magma • High viscosity (thick)…very explosive

  10. Volcano Diagram

  11. Volcano Diagram

  12. 18.2 Learning Objectives • Explain what plutons are. • Describe each of the 5 types of plutons. • Identify each of the 5 types of plutons.

  13. How does magma behave beneath the Earth’s surface? • Magma interacts with the crust in several ways. • Plutons: igneous (volcanic) rock and magma within the Earth’s crust

  14. What are the 5 major types of plutons?

  15. What are the 5 major types of plutons? • 1) Batholiths • Large (100 sqare kilometers or more) irregularly-shaped masses of igneous rock or magma. • Form 10-30 km below Earth’s surface.

  16. What are the 5 major types of plutons? • 2) Stocks • Similar to batholiths, but SMALLER. • Form 10-30 km below Earth’s surface. • May be batholiths that are only partly exposed.

  17. What are the 5 major types of plutons? • 3) Laccoliths • Mushroom-shaped pluton…round top and flat bottom. • Smaller than batholiths and stocks.

  18. What are the 5 major types of plutons? • 4) Sill • A pluton that is parallel (runs along) existing layers of rock in Earth’s crust. • 5) Dike • A pluton that cuts across existing layers of rock in Earth’s crust.

  19. Why are plutons important? • BATHOLITHS are found within the cores of many mountain ranges. • MOST of the Earth’s “igneous activity” takes place INSIDE the Earth (within plutons) and NOT within volcanoes…most magma never reaches Earth’s surface!!!

  20. 18.3 Learning Objectives • Explain the features of each of the 3 types of volcanoes, including magma. • Describe each type of tephra. • Describe the different places volcanoes occur.

  21. What are the 3 major types of volcanoes? • 1) Shield Volcano • Broad, gently sloping sides and a circular base. • Non-explosive eruptions…basaltic lava!! • Found in Hawaii

  22. What are the 3 major types of volcanoes?

  23. What are the 3 major types of volcanoes? • 2) Cinder-cone volcano • Small (less than 500m high) with steep-sloping sides. • Explosive eruptions…magma has high viscosity!!

  24. What are the 3 major types of volcanoes?

  25. What are the 3 major types of volcanoes? • 3) Composite volcano • Larger than cinder-cone volcanoes, but smaller than shield volcanoes. • Medium-sloping sides. • Very explosive….very dangerous!! • Mount St. Helens is a composite volcano.

  26. What are the 3 major types of volcanoes?

  27. What are some features of volcanoes? • Crater : the bowl-shaped depression at the top of a volcano, around the vent. • Caldera : Larger depressions formed at the top or the side where part of the volcano has collapsed into the magma chamber.

  28. What comes out of a volcano? • In addition to lava and ash, other stuff comes of volcanoes too!! • The other stuff is called Pyroclastic flow • VERY deadly • 1) Ash • 2) Lapilli…”little stones” • 3) Blocks…huge car/house-sized rocks • 4) Bombs…huge blobs of lava that solidify in the air (or are ‘pancaked’ when they hit the ground)

  29. Where do volcanoes occur? • 80% of all volcanoes are found at convergent boundaries • When one plate moves beneath another plate (subduction), melts, and rises again. • Ring of Fire – an area of frequent earthquakes and volcanic eruptions encircling the basin of the Pacific Ocean.

  30. Where do volcanoes occur?

  31. Where do volcanoes occur? • 15% found at divergent boundaries • Mid-Ocean ridges!! • 5% away from plate boundaries • Hot spots…really hot locations in the middle of plates. • Hawaii

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