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Section 2: Volcanic Activity

Section 2: Volcanic Activity. Friday, March 12, 2010 Pages 183 -- 192. Arenal Volcano -- Costa Rica. Objectives. Describe what happens when a volcano erupts. Explain how the two types of volcanic eruptions differ depending on the characteristics of magma. Identify some hazards of volcanoes

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Section 2: Volcanic Activity

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  1. Section 2: Volcanic Activity Friday, March 12, 2010 Pages 183 -- 192 Arenal Volcano -- Costa Rica

  2. Objectives • Describe what happens when a volcano erupts. • Explain how the two types of volcanic eruptions differ depending on the characteristics of magma. • Identify some hazards of volcanoes • Identify types of volcanic activity other than eruptions.

  3. Magma chamber Pipe Vent Lava flow Crater Silica Pahoehoe Aa Pyroclastic flow Active Dormant Extinct Hot spring Geyser Geothermal energy Vocabulary Words

  4. Origin of Magma • Lava begins as magma in the mantle. • The magma is under great pressure • Magma flows upward because it’s less dense than surrounding materials. • Magma will continue to rise until it reaches the surface or until it becomes trapped beneath rock.

  5. Volcanic Eruptions • The trapped gases found in magma are under great pressure. • Ex: soda bottle • As the magma reaches the surface, the pressure decreases. • The gases begin to separate out, forming bubbles. • During volcanic eruption, the gases dissolved in the magma rushes out, carrying the magma with them. Stromboli -- off the North coast of Sicily.

  6. Exploring a Volcano Dust Cloud Crater Vent Side Vent Pipe Lava Flow Lava Magma Magma Chamber

  7. Characteristics of Magma • There are many types of magma. • Some are thick and flows slowly. • Some are fluid and flow very easily. • The temperature of the magma will determine how it flows.

  8. The Role of Silica • The amount of silica in magma also helps to determine how easily the magma flows. • What is silica? • It’s a material formed from 2 different elements -- oxygen and silicon. • There are lots of silica found on the Earth’s crust and mantle.

  9. The Role of Silica -- Cont’d • The more silica magma contains, the thicker it is. • Magma with a lot of silica produces light-colored lava. • Rhyolite is an example of a rock formed from magma with lots of silica. Rhyolite

  10. Role of Silica -- Cont’d • Magma that is low in silica flows easily and produces dark-colored lava. • Basalt is an example of a rock with very little silica.

  11. Types of Volcanic Eruptions • The type of magma that flows from a volcano will determine whether the eruption is quiet or explosive.

  12. Quiet Eruptions • If the magma flows easily, the eruption will be quiet. • This is because the gases in the magma bubble out slowly. • The lava is usually thin and runny. • There are 2 types of lava produced this way. • Pahoehoe • aa

  13. Pahoehoe • Fast moving • Looks wrinkled, rope-like

  14. aa • This type of lava is cooler. • It is slower-moving. • When cooled, the surface is jagged and chunky.

  15. Explosive Eruptions • Eruptions are explosive if the magma is thick and sticky. • The thick magma prevents the lava from flowing freely. • Instead, the magma builds up slowly in the pipe and acts as a plug. • The trapped gases build up until it explodes.

  16. Explosive Eruptions -- Cont’d • The lava is pushed out violently. • The lava is broken into fragments that cool quickly. • Can be as small and fine as volcanic ash • Can be as large as a car • This type of flow is called pyroclastic flow.

  17. Mount St. Helen • This is an example of pyroclastic flow.

  18. Stages of a Volcano • Active • The volcano is alive. • Dormant • The volcano is asleep. • Extinct • The volcano is unlikely to erupt again.

  19. Other Types of Volcanos • Hot Springs • Formed from the heating of underground water by a nearby body of magma • This water may contain dissolved gases and other substances found deep within the Earth. Mt. Princeton Hot Springs, CO

  20. Other Types of Volcanos • Hot Springs • Formed from the heating of underground water by a nearby body of magma • This water may contain dissolved gases and other substances found deep within the Earth. Mt. Princeton Hot Springs, CO

  21. Other Types of Volcanoes • Geyser is a fountaiin of water and steam that erupts from the ground. • This is a result of water and steam that is trapped underground. Old Faithful -- Yellowstone

  22. Geothermal Energy • This is a form of alternative energy. • This form of energy is clean and reliable. • Is energy source is used in Iceland, northern California and New Zealand.

  23. Homework • Workbook 6.2 (3/15) • Vocabulary quiz 6.2 (3/17) • Workpacket 6.2 (3/17)

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