GEOLOGY MEDIA SUITE Chapter 12

UNDERSTANDING EARTH, SIXTH EDITION GROTZINGER JORDAN GEOLOGY MEDIA SUITE Chapter 12 Volcanoes 2010 W.H. Freeman and Company

Plate tectonics explains the global pattern of volcanism. Key Figure 12.20 (page 285) Go to next slide to begin

Island arc Active volcano over hot spot Continental volcanic belt Mid-ocean ridge Extinct volcano Ocean plate Rising magma Hot spot Mantle plume Continental crust Continental mantle lithosphere

At ocean-ocean convergent boundaries, magmas give rise to volcanic island arcs erupting mostly basaltic lavas. Island arc Active volcano over hot spot Continental volcanic belt Mid-ocean ridge Extinct volcano Ocean plate Rising magma Hot spot Mantle plume Continental crust Continental mantle lithosphere

At ocean-ocean convergent boundaries, magmas give rise to volcanic island arcs erupting mostly basaltic lavas. Island arc Active volcano over hot spot Mid-ocean ridge Magmas formed at ocean-continent convergences give rise to volcanoes erupting andesitic lavas. Extinct volcano Continental volcanic belt Ocean plate Rising magma Hot spot Mantle plume Continental crust Continental mantle lithosphere

At ocean-ocean convergent boundaries, magmas give rise to volcanic island arcs erupting mostly basaltic lavas. Island arc Active volcano over hot spot Mid-ocean ridge Magmas formed at ocean-continent convergences give rise to volcanoes erupting andesitic lavas. Extinct volcano Continental volcanic belt Ocean plate Rising magma Hot spot Plate separation at a mid-ocean ridge results in basaltic volcanism. Mantle plume Continental crust Continental mantle lithosphere

At ocean-ocean convergent boundaries, magmas give rise to volcanic island arcs erupting mostly basaltic lavas. Island arc Active volcano over hot spot Mid-ocean ridge Magmas formed at ocean-continent convergences give rise to volcanoes erupting andesitic lavas. Extinct volcano Continental volcanic belt Ocean plate Rising magma Hot spot Plate separation at a mid-ocean ridge results in basaltic volcanism. Plate motion over hot spots creates midplate chain of basaltic volcanic islands. Mantle plume Continental crust Continental mantle lithosphere

Plate tectonics explains the global pattern of volcanism. Which volcanic environment will, on average, produce the most felsic lavas? A. Mid-ocean ridge B. Island arc C. Continental arc D. Oceanic hotspot

Plate tectonics explains the global pattern of volcanism. What composition volcanic rocks characterize magmatism at mid-ocean ridges? A. Carbonitite B. Basalt C. Andesite D. Rhyolite

Plate tectonics explains the global pattern of volcanism. True or False: Asthenosphere melting at mantle plumes is triggered by decompression. A. True B. False

Plate motion and the age of volcanoes Figure 12.21 (page 287) Go to next slide to begin

Older extinct volcanoes Direction of plate movement Hot-spot volcano Lithosphere Asthenosphere Hot-spot

The Pacific Plate has moved northwest over the Hawaiian hot spot Older extinct volcanoes Direction of plate movement Hot-spot volcano Lithosphere Asthenosphere Hot-spot

The Pacific Plate has moved northwest over the Hawaiian hot spot Older extinct volcanoes Direction of plate movement Lithosphere Hot-spot volcano ASIA Emperor Seamounts Midway NORTH AMERICA Asthenosphere Hawaii Equator PACIFIC OCEAN Hot-spot Tahiti Galápagos Islands

The Pacific Plate has moved northwest over the Hawaiian hot spot resulting in a chain of volcanic islands. Older extinct volcanoes Direction of plate movement Lithosphere Hot-spot volcano ASIA Emperor Seamounts Midway NORTH AMERICA Asthenosphere Hawaii Equator PACIFIC OCEAN Hot-spot Tahiti Galápagos Islands

The Pacific Plate has moved northwest over the Hawaiian hot spot resulting in a chain of volcanic islands. Older extinct volcanoes Direction of plate movement Lithosphere Asthenosphere Hot-spot volcano Hot-spot ASIA Emperor Seamounts Midway Hawaii Equator PACIFIC OCEAN Tahiti NORTH AMERICA Galápagos Islands 64.7 Ma 56.2 55.4 55.2 48.1 39.9 43.4 Midway 27.7 42.4 Nihau 5.5 Kilauea 0 Hawaii hot spot Direction of plate movement

The Pacific Plate has moved northwest over the Hawaiian hot spot resulting in a chain of volcanic islands. The ages of the mountains suggest plate movement of about 100 mm/yr Older extinct volcanoes Direction of plate movement Lithosphere Asthenosphere Hot-spot volcano Hot-spot ASIA Emperor Seamounts Midway Hawaii Equator PACIFIC OCEAN Tahiti NORTH AMERICA Galápagos Islands 64.7 Ma 56.2 55.4 55.2 48.1 39.9 43.4 Midway 27.7 42.4 Nihau 5.5 Kilauea 0 Hawaii hot spot Direction of plate movement

PACIFIC OCEAN Washington Oregon Idaho Montana Yellowstone Caldera Chain Wyoming 16.1 15.5 13.7 13.8 13.8 12.5 11 4.3 10.3 6.6 6.2 1.8 2.0 0.8 Ma Hot spot Yellowstone National Park California Nevada Utah 15.6 14.7

1.8 2.0 0.8 Ma Hot spot 16.1 15.5 13.7 13.8 13.8 12.5 11 4.3 10.3 6.6 6.2 Yellowstone National Park 15.6 14.7

The North American Plate is moving southwest over the Yellowstone hot spot. 1.8 2.0 0.8 Ma Hot spot 16.1 15.5 13.7 13.8 13.8 12.5 11 4.3 10.3 6.6 6.2 Yellowstone National Park 15.6 14.7

Plate motion and the age of volcanoes True or False: In order to determine absolute plate motions using hotspot tracks, hotspot positions must remain fixed relative to one another. A. True B. False

Plate motion and the age of volcanoes What does the Hawaiian hotspot track indicate about the change in Pacific plate motion that occurred 43 million years ago? A. Plate motion changed from a southerly to a southeasterly direction. B. Plate motion changed from a southeasterly to a southerly direction. C. Plate motion changed from a northwesterly to a northerly direction. D. Plate motion changed from a northerly to a northwesterly direction.

Plate motion and the age of volcanoes Select the most accurate direction of motion for the North American plate as indicated by the Yellowstone hotspot track. A. Northwest B. Northeast C. Southwest D. Southeast

Cinder Cones of Arizona What composition of magma has been erupted to form the cinder cones of the San Francisco Volcanic Field? A. Ultramafic B. Mafic C. Intermediate D. Felsic

Cinder Cones of Arizona True or False: A cinder cone records a long history of volcanic activity because it is a long-lived feature, forming over many eruptions from the same eruptive vent. A. True B. False

Cinder Cones of Arizona Which is the appropriate scale for the height of SP Crater, a typical cinder cone? A. 10 meters B. 300 meters C. 3 kilometers D. 10 kilometers

White Island Stratovolcano With which plate-tectonic environment are stratovolcanoes most commonly associated? A. Continent-continent collision zones B. Subduction zones C. Mid-ocean ridges D. Oceanic transforms E. Continental transforms

White Island Stratovolcano What triggers the magmatism that leads to the development of volcanic arcs near subduction zones? A. Frictional heating of the non-subducting plate B. Melting of the subducted oceanic lithosphere C. Melting of subducted continental lithospere D. Addition of water into the asthenosphere

White Island Stratovolcano Which of the following best characterizes the make-up of a Stratovolcano like White Island Volcano? A. Made primarily of lava flows B. Made primarily from pyroclastic deposits C. Made of a mix of lava flows and pyroclastic deposits

White Island Stratovolcano Which of the following central-vent volcanic constructs is typically the largest? A. Cinder cone B. Stratovolcano C. Shield volcano D. Volcanic dome

White Island Stratovolcano Which of the eruptive conditions listed below is most appropriate to the formation of stratovolcanoes? A. Relatively non-explosive eruption of fluid mafic lava flows B. Intermediate composition pyroclastic eruptions and lava flows C. Fissure eruptions of basaltic lava D. Mafic pyroclastics mixed with rhyolite pahoehoe lava

White Island Hydrothermal Select the tectonic setting(s) in which hydrothermal activity commonly occurs. A. Island arc volcanoes B. Mid-ocean ridges C. Continental hotspots D. All of the above

White Island Hydrothermal Which of the following is not a gas emitted by White Island Volcano (and volcanoes, in general)? A. Carbon dioxide (CO 2 ) B. Sulfur dioxide (SO 2 ) C. Water (H 2 0) D. Oxygen (O 2 ) E. Hydrogen Chloride (HCl)

White Island Hydrothermal True or False: When gas emissions from volcanoes dissolve in water they lower the ph of the water. A. True B. False

Lava Flows and Features Aa lava flows and clinker develop from: A. Slow moving sticky lava B. Fast moving runny lava C. Pyroclastic eruptions D. Eruption under water

Lava Flows and Features In volcanic rocks, aphanitic texture refers to a texture involving: A. Mostly glassy rocks B. Frozen gas bubbles C. Crystals only visible with a microscope

Lava Flows and Features Vesicular texture is produced when get trapped as lava solidifies into solid rock. A. Crystals B. Bubbles C. Xenoliths

Lava Flows and Features In igneous rocks, xenoliths are: A. Clusters of crystal that formed after eruption B. Rocks erupted by a volcano C. Foreign rock fragments

Volcano Lessons What kinds of data are used in predicting volcanic activity? A. Seismic data B. Chemistry of volcanic gases C. Changes in volcano shape D. All of the above

Volcano Lessons True or False: Mount St. Helens last erupted in 1980 and has been inactive since that time. A. True B. False

Volcano Lessons Mount St. Helen s is what kind of volcanic construct? A. Stratovolcano B. Shield volcano C. Basalt Plateau D. Cinder cone

Volcano Lessons Mount St. Helens and other Cascade Range volcanoes exist as a result of what geologic process? A. Continental rifting B. Hotspot volcanism C. Ocean-continent convergence D. Flood basalt volcanism

Volcano Lessons Select the volcanic hazard that did not result from the 1980 eruption of Mount St. Helens. A. Flank collapse B. Lahar C. Pyroclastic flow D. Eruption cloud E. Lava flow

Volcanic Development In which of the following tectonic environments would you expect to find this type of volcanism? A. hot-spot B. subduction zone C. continental rift D. all of these E. all of these

Volcanic Development When molten rock is below the ground it is referred to as, but when it reaches the surface it is called. A. lava; a pluton B. magma; lava C. hydrothermal; magma D. lava; magma

Volcanic Development What force is responsible for moving molten rock to the surface? A. gravity B. friction C. normal force D. buoyancy force

Volcanic Development If you reached down and picked up an igneous rock composed of interlocking mineral crystals big enough to see, what could you say about the geologic conditions under which it formed? A. The rock is a remnant of a magma body that cooled underground. B. The rock was blasted out by an explosive volcanic eruption. C. The rock was formed when a lava flow made contact with nearby ocean water. D. The rock was cemented together when ash and cinders were washed into a lake basin.

Volcanic Development Evaluate the following statements and indicate the one that seems most consistent with geologic data. A. All magma chambers will generate volcanoes. B. All volcanoes will produce extrusive igneous rock. C. All igneous intrusions cool rapidly below the surface. D. All plate boundaries are associated with explosive volcanic activity.

Composite Volcano Steep-sided volcanoes that produce alternating layers of lava and pyroclastic material are called? A. shield volcanoes B. cinder cones C. fissure eruptions D. composite volcano

Composite Volcano Composite volcanoes are most often produced by magma plumes associated with: A. a continental rift margin. B. subduction along a convergent margin. C. the edges of a transform margin. D. all of these E. none of these

Composite Volcano Which of the following statements is true? A composite volcano differs from a shield volcano in that a shield volcano: A. is less explosive B. produces more felsic lavas C. has steeper sides D. is only found in association with hot spots

Composite Volcano What type of evidence do volcanologists rely on to predict explosive volcanic activity? A. more frequent earthquakes near the volcano B. measurable bulging of the volcano s slopes C. increased emissions of sulfur and carbon-rich gases D. all of these E. none of these

Composite Volcano Which one of the following famous volcanoes would best be described as a composite volcano? A. Mauna Loa, Hawaii B. Mt. St. Helens, Washington C. Devils Tower, Wyoming D. Sunset Crater, Arizona