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

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Presentation on theme: "Question of the Day Question: How do we find the epicenter of an earthquake? Answer: ……… Turn In: -A Whole Lot of Shakin’ -Finding an Earthquake’s Epicenter."— Presentation transcript:

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

2 Lava & Volcanoes

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4 Types of Lava Composition Felsic lava/magma –-sic = silica = quartz = SiO 2 –Forms continental crust –Lighter colored rocks –lower density rocks Quartz GraniteFeldspar

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 –Magma from the mantle rises to the surface –Magma melts through oceanic crust only –Very little SiO 2 is picked up by the magma –Erupting lava is mafic in composition

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

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

9 Felsic Lava –Magma from the mantle rises toward the surface –Magma melts through continental crust –Lots of SiO 2 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? A.Continental/Oceanic Convergent B.Oceanic/ Oceanic Convergent C.Continental/ Continental Convergent D.Transform

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

12 Why is SiO 2 important? SiO 2 thickens lava –Changes appearance of igneous rocks produced –Changes types of volcanoes produced –Changes the style of eruptions from those volcanoes

13 SiO 2 & Rocks SiO 2 makes igneous rocks lighter in color Which of these rocks is felsic? A. Granite B. Basalt

14 SiO 2 & Rocks SiO 2 makes igneous rocks lighter in color Which of these rocks is felsic? A. Granite- FELSIC B. Basalt- MAFIC

15 SiO 2 & Rocks Since felsic lava is formed from continental crust, felsic rocks will be _______________ than mafic rocks A.Denser B.Less dense C.Heavier D.Darker

16 SiO 2 & Rocks Since felsic lava is formed from continental crust, felsic rocks will be _______________ than mafic rocks A.Denser B.Less dense C.Heavier D.Darker

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

19 Properties of Felsic Lava High viscosity makes it difficult for volcanic gases (CO 2,SO 2, H 2 O) 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. ExplosiveB. 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 Mauna Loa, Hawaii Kilauea, Hawaii

26 What about hot spots? Hawaii –Magma melts through oceanic crust so lava is A.MaficB. Felsic

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

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

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

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