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

2. 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.

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

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

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

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

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

8. 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

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

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

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

12. 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?

13. 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

14. 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

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

17. 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

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

19. 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

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

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

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

23. 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

24. 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

25. 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

26. 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

27. 27

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