Unit 3 Module 1 Volcano Hand-out

UNIT 3 MODULE 1 VOLCANOES

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Plants in the Philippines: Tiwi, Albay Kidapawan, North Cotabato Calacan, Laguna Tongonan, Leyte Bago City, Negros Occidental Valencia, Negros Oriental Bacon, Sorsogon Power plants are built in an area where it is particularly hot just below the surface such as near a group of geysers, hot springs, or volcanic activity. How is geothermal energy generated?  Wells are drilled 1 or 2 miles deep into the Earth to pump steam or hot water to the surface.  Mostly found in area with hot springs, geysers, or volcanic activity.

What determines eruption style? The crystal and gas content and temperature of a magma help determine a volcano's eruption style. 1. Crystals (silica content) in magma make it more viscous, so magma with a high crystal content is more likely to explode than flow. 2. Gases create explosions if they cannot easily escape from viscous magma, but they can also be released without explosions (or with only minor ones) from fluid magma. 3. High-temperature magmas usually erupt effusively, while low-temperature magmas cannot flow easily and are more likely to erupt explosively. TYPES OF VOLCANIC ERUPTION a. Phreatic – a steam-driven eruption. Characterized by fine ash column. b. Phreatomagmatic – steam-driven (violent) eruption with inclusion of molten magma. Characterized by large columns of fine ash and high-speed pyroclastic emission. c. Strombolian – a periodic of weak to violent eruption characterized by fountain lava. d. Vulcaninan – characterized by tall eruption columns that reach up to 20km high with pyroclastic flow and ashfall tephra. e. Plinain – excessively explosive type of eruption of gas and pyroclastics. 

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A pyroclastic flow - is a fast-moving current of hot gas and rock (collectively known as tephra), which reaches speeds moving away from a volcano of up to 700 km/h (450 mph). The gas can reach temperatures of about 1,000 °C (1,830 °F). Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size or emplacement mechanism.

Tephra fragments are classified by size:  Ash – particles smaller than 2 mm (0.08 inches) in diameter,  Lapilli or volcanic cinders – between 2 and 64 mm (0.08 and 2.5 inches) in diameter,  Volcanic bombs or volcanic blocks – larger than 64 mm (2.5 inches) in diameter. The words "tephra" and "pyroclast" both derive from Greek. Tephra means "ash". Pyro means "fire" and klastos means "broken"; thus pyroclasts carry the connotation of "broken by fire".

ENERGY FROM THE VOLCANO Geothermal energy – the heat from the earth’s interior as a source of energy.

How It Works

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Hot water is pumped from deep underground through a well under high pressure. When the water reaches the surface, the pressure is dropped, which causes the water to turn into steam. The steam spins a turbine, which is connected to a generator that produces electricity. The steam cools of in a cooling tower and condenses back to water. The cooled water is pumped back into the Earth to begin the process again.

Efects of Volcanic Eruptions Despite from its bad effect such as loss of lives and destruction properties, there are other good effect of volcanic eruption. 1. Decrease in the earth’s surface temperature 2. Production of rich soil for farming 3. Creation of landscapes and generates tourism 4. Production of earthenware out of ashfall. Signs of Impending Volcanic Eruptions: 1. Increase in the frequency of volcanic quakes with rumbling sounds; occurrence of volcanic tremors 2. Increased steaming activity; change in color of steam emission from white to gray due to entrained strash 3. Crater glow due to presence of magma at or near the crater 4. Ground swells (or inflation, ground tilt and ground fissuring due to magma intrusion 5. Localize landslides, rockfall and landslides from the summit area which not attributable to heavy rains 6. Noticeable increase in the extent of drying up vegetation around the volcano’s upper slopes 7. Increase in the temperature of hot springs, wells, and crater lake

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Noticeable variation in the chemical content of the springs, crater lakes within the vicinity of the volcano Drying up of springs/wells around the volcano; and,

10. Development of new thermal areas and/or reactivation of old ones; appearance of solfataras. For more information: visit this page:

http://mail.colonial.net/~hkaiter/volcanoes.html