Inside Earth Chapter 3.2 Pages 93-102 Volcanic Activity Inside Earth Chapter 3.2 Pages 93-102

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.

Characteristics of Magma Silica: a material found in magma composed of the elements silicon and oxygen More silica = thicker magma Low Silica = runny magma

Volcanic Rocks High Silica makes light colored rock Rhyolite an extrusive igneous rock

Volcanic Rocks High Silica makes light colored rock Pumice spaces left in the rock by gases bubbling out.

Volcanic Rocks Low Silica makes dark colored rock Obsidian- cools very quickly giving a glassy texture.

Volcanic Rocks Low Silica makes dark colored rocks Basalt dark colored extrusive igneous rock

Types of Volcanic Eruptions A volcano’s magma influences how the volcano erupts The silica content helps determine whether the volcanic eruption is… Quiet or... Explosive! 8

Quiet Eruptions Lava: oozes out; is runny and flows smoothly Gases: bubble out gently Examples: Iceland and Hawaii. 9

Aa Cooler, slow moving lava Forms jagged chunks of lava. 10

Pahoehoe Fast moving, hot lava Surface of lava looks like a solid mass of wrinkles, billows and ropelike coils. 11

How does the amount of silica in magma affect the type of eruption? Exit Pass How does the amount of silica in magma affect the type of eruption?

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. 13

Volcanic Projectiles Volcanic Ash Cinders Bombs Rocky, sand-sized particles Cinders Pebble-sized particles Bombs Large pieces of rock (baseball to the size of a car). 14

Explosive Eruptions Pyroclastic Flow Occurs when an explosive eruption hurls out ash, cinders and bombs as well as gases (400mph, 1,800˚F). 15

Volcano Hazards Time between eruptions can span hundreds of years (Dormant Volcano) People may be unaware of the danger Mt. Saint Helens 123 years. 17

Volcano Hazards Lahar: A mud flow caused by melted snow or river Carries ash, trees and rocks. 18

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. 19

Volcano Hazards Pompeii, A.D. 79 Buried for 1700 years under 12 feet of ash 20

What is one type of volcanic projectile? What is a Lahar? Exit Pass What is one type of volcanic projectile? What is a Lahar?

Other Volcanic Activity Hot Spring: pool of groundwater is heated by a nearby body of magma 22

Other Volcanic Activity 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. 23

Other Volcanic Activity 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. 24

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. 25

Monitoring Volcanoes 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. 26

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What is the difference between a Hot Spring and a Geyser? Exit Pass What is the difference between a Hot Spring and a Geyser?