1. Finding an Earthquake’s Epicenter
Question of the Day
Question: How do we find the epicenter of an earthquake? Answer: … … …
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A Whole Lot of Shakin’
Finding an Earthquake’s Epicenter

2. Lava & Volcanoes

4. Types of Lava Composition
Felsic lava/magma
-sic = silica = quartz = SiO2
Forms continental crust
Lighter colored rocks
lower density rocks
Quartz
Granite
Feldspar

5. Types of Lava Composition
Mafic lava/magma
-fic = ferric = Fe = iron
Forms oceanic crust
Darker colored rocks
higher density rocks
Hornblende
Basalt

6. Mafic Lava Mafic Lava Magma from the mantle rises to the surface
Magma melts through oceanic crust only
Very little SiO2 is picked up by the magma
Erupting lava is mafic in composition

7. Mafic Lava At which plate boundaries does mafic lava erupt?
Continental/Oceanic Convergent
Oceanic/ Oceanic Convergent
Continental/ Continental Convergent
Divergent

8. Mafic Lava At which plate boundaries does mafic lava form?
B. Oceanic/ Oceanic Convergent
D. Divergent

9. Felsic Lava Felsic Lava Magma from the mantle rises toward the surface
Magma melts through continental crust
Lots of SiO2 is picked up by the magma from the continental crust
Erupting lava is felsic in composition

10. Felsic Lava At which plate boundaries does felsic lava form?
Continental/Oceanic Convergent
Oceanic/ Oceanic Convergent
Continental/ Continental Convergent
Transform

11. Felsic Lava At which plate boundaries does felsic lava form?
Continental/Oceanic Convergent

12. Why is SiO2 important? SiO2 thickens lava
Changes appearance of igneous rocks produced
Changes types of volcanoes produced
Changes the style of eruptions from those volcanoes

13. SiO2 & Rocks SiO2 makes igneous rocks lighter in color
Which of these rocks is felsic?
B. Basalt
A. Granite

14. SiO2 & Rocks SiO2 makes igneous rocks lighter in color
Which of these rocks is felsic?
B. Basalt- MAFIC
A. Granite- FELSIC

15. SiO2 & Rocks
Since felsic lava is formed from continental crust, felsic rocks will be _______________ than mafic rocks
Denser
Less dense
Heavier
Darker

16. SiO2 & Rocks
Since felsic lava is formed from continental crust, felsic rocks will be _______________ than mafic rocks
Denser
Less dense
Heavier
Darker

17. Properties of Felsic Lava
Very thick, slow-moving (high viscosity)
Lava cools before it moves very far
Volcanoes are
Narrow with steep
sides
Wide with shallow
sloping sides

18. Properties of Felsic Lava
Very thick, slow-moving (high viscosity)
Lava cools before it moves very far
Volcanoes are
Narrow with steep
sides
Wide with shallow
sloping sides

19. Properties of Felsic Lava
High viscosity makes it difficult for volcanic gases (CO2,SO2, H2O) to escape
Trapped gases cause eruptions to be more explosive
Mt. Pinatubo
1991

20. Composite Cone/Stratovolcano
Up to 22,000 feet tall
steep-sided, symmetrical cones
Eruptions are extremely explosive
Mount Fuji , Japan

21. Composite Cone/Stratovolcano
alternating layers of lava flows, volcanic ash, and rocks.
Created from felsic lava

22. Volcanic Dome/ Lava Dome
Rebuilding Stratovolcano
Steep sides because lava cools quickly, before spreading out
Created by felsic lava
Eruptions are extremely explosive
Mt. St. Helens, WA (before and after)

23. Properties of Mafic Lava
Thin, fast- moving lava/magma (low viscosity)
Lava spreads out and cools
Produces wide volcanoes
Volcanic gases escape easily
Eruptions are _______________
A. Explosive B. Not very explosive

24. Properties of Mafic Lava
Thin, fast- moving lava/magma (low viscosity)
Lava spreads out and cools
Produces wide volcanoes
Volcanic gases escape easily
Eruptions are _______________
B. Not very explosive

25. Shield Volcano broad, gentle slopes
Created by fluid mafic lava that spreads out quickly before cooling
largest volcanoes on Earth
Kilauea, Hawaii
Mauna Loa, Hawaii

26. What about hot spots? Hawaii
Magma melts through oceanic crust so lava is
Mafic B. Felsic

27. What about hot spots? Hawaii
Magma melts through oceanic crust so lava is
Mafic

28. What about hot spots? Hawaii Yellowstone
Magma melts through oceanic crust so lava is
Mafic
Yellowstone
Magma melts through continental crust so lava is
A. Mafic B. Felsic

29. What about hot spots? Hawaii Yellowstone
Magma melts through oceanic crust so lava is
Mafic
Yellowstone
Magma melts through continental crust so lava is
B. Felsic
It all depends on the type of crust it’s under!