Inside Earth Chapter 3.2 Pages 93-102
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Transcript of Inside Earth Chapter 3.2 Pages 93-102
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Inside Earth Chapter 3.2Pages 93-102
Volcanic Activity
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Characteristics of Magma• Force of an eruption depends partly on the
amount of gases evaporated in the magma• The temperature and the contents of the
magma are important factors.
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Characteristics of Magma• Silica: a material found in magma composed
of the elements silicon and oxygen–More silica = thicker magma– Low Silica = runny magma
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• High Silica makes light colored rock–Rhyolite an extrusive igneous rock
Volcanic Rocks
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• High Silica makes light colored rock–Pumice spaces left in the rock by gases
bubbling out.
Volcanic Rocks
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• Low Silica makes dark colored rock–Obsidian- cools very quickly giving a glassy
texture.
Volcanic Rocks
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• Low Silica makes dark colored rocks–Basalt dark colored extrusive igneous rock
Volcanic Rocks
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Types of Volcanic Eruptions
• A volcano’s magma influences how the volcano erupts
• The silica content helps determine whether the volcanic eruption is…
Quiet Explosive!or...
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Quiet Eruptions• Lava: oozes out; is runny
and flows smoothly
• Gases: bubble out gently
• Examples: Iceland and Hawaii.
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Aa
• Cooler, slow moving lava• Forms jagged chunks of lava.
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Pahoehoe
• Fast moving, hot lava• Surface of lava looks like a solid mass of
wrinkles, billows and ropelike coils.
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Exit PassHow does the amount of silica in
magma affect the type of eruption?
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Explosive Eruptions• Lava: thick and sticky; builds up
in the pipe, plugging it like a cork in a bottle
• Gases: Pressure builds up until gas forces its way past magma, causing the volcano to erupt violently.
• Example: Mount Saint Helens.
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Volcanic ProjectilesVolcanic Ash• Rocky, sand-sized particles
Cinders• Pebble-sized particles
Bombs• Large pieces of rock (baseball to the size of a car).
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Explosive Eruptions• Pyroclastic Flow• Occurs when an explosive eruption hurls out ash,
cinders and bombs as well as gases (400mph, 1,800˚F).
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Volcano Hazards• Time between eruptions can span hundreds of
years (Dormant Volcano)– People may be unaware of the danger– Mt. Saint Helens 123 years.
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Volcano Hazards
• Lahar:– A mud flow
caused by melted snow or river
– Carries ash, trees and rocks.
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Volcano Hazards• Volcanic Ash:– Bury towns, damage crops, and clog car engines– Wet ash is heavy and can cause roofs to collapse– Plane engines can fail if pulled into the engine.
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Volcano Hazards• Pompeii, A.D. 79• Buried for 1700 years
under 12 feet of ash
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Exit PassWhat is one type of volcanic projectile? What is a Lahar?
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Other Volcanic Activity
• Hot Spring: pool of groundwater is heated by a nearby body of magma
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• Geyser - fountain of water and steam that erupts from the ground– Hot water and steam
that become trapped underground
– Builds up pressure until it gushes out of the ground.
Other Volcanic Activity
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• Geothermal Energy - clean, reliable energy source provided by magma-heated water – Hot water can be piped
into homes– Steam is piped into a
turbine that spins and generates electricity.
Other Volcanic Activity
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Monitoring Volcanoes• Changes around a volcano shows signs of an
eruption and allow short time for a warning– Tiltmeters and Laser ranging devices to see ground
changes due to shifting magma– Monitor escaping gases and water level in a
volcano's crater lake.
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• Check the temperature of the ground water to see if the magma is heating it
• Monitor the many small earthquakes triggered by magma moving from the chamber to the pipe
• Still, unable to predict the strength or exact time of the eruption.
Monitoring Volcanoes
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Exit PassWhat is the difference between
a Hot Spring and a Geyser?