Q&A Hero

Q: Fault-block mountains form only along divergent plate boundaries.

Q: Instead of subduction down into the mantle, the Indian subcontinent was thrust beneath Tibet, helping to significantly raise the landscape.

Q: Passive continental margins will have a well-developed forearc and back-arc basin system.

Q: Forearc basins will consist of thick sequences of highly deformed sedimentary rocks.

Q: The subduction and melting of an accretionary wedge will result in a secondary magma.

Q: Volcanic island arc activity is short-lived and as a result will only produce tiny islands.

Q: The depth of deep-ocean trenches is closely related to age: the younger the subducting plate, the deeper the trench.

Q: Most mountain ranges formed through cooling of the Earth's crust, which resulted in wrinkling as it contracted.

Q: How would the angle of subduction of a tectonic plate influence the location of a volcanic arc? A) The steeper the angle, the closer the arc would form to the trench B) The shallower the angle, the closer the arc would form to the trench C) The steeper the angle, the further the arc would form to the trench D) The angle of subduction doesn't affect the location of the volcanic arc

Q: Why would geologic mapping be difficult in an area dominated by accreted terranes? A) The geology is so similar that it would be difficult to determine terrane boundaries B) Each terrane is geologically distinct, but also highly deformed C) Isostatic rebound would result in gravitational collapse to make them indistinct D) Terranes are very old and terribly eroded

Q: What is one possible explanation for the crustal subsidence that created extensive areas of downwarping such as in Michigan and Illinois? A) Cessation of compression along a convergent plate boundary B) Cessation of upwelling from a mantle plume C) Cessation of subduction, with detachment of the descending slab, creates a downward pull in the mantle D) The crust is extended to maintain a convergent plate boundary where the descending plate is sinking

Q: Which of the following is believed to be responsible for uplifting southern Africa 1,500 meters higher than what would be expected for a stable continental platform? A) Microcontinents B) Isostacy C) Orogenesis D) Superplume

Q: Which of the following best describes the effect of convective flow on the elevation of Earth's major landforms? A) Convective flow adds more material to the base of the lithosphere, making it downwarp. B) Rotation of convecting mantle material smoothes out wrinkles in the surface. C) Hot rising material upwarps the landscape whereas downward flow causes downwarping. D) Subduction of oceanic plates disrupting the convective flow on the mantle, resulting in hot spots burning through the crust.

Q: Which of the following terms describes the increasing downward force on basal rocks as a mountain continues to grow? A) Isostacy B) Delamination C) Accretion D) Gravitational collapse

Q: Which of the following is a real-world example of isostatic adjustment? A) Continental margin of North America extending to create a forearc basin in California B) African continent bulging upward when moving over a mantle plume C) Downwarping of the continent in Illinois due to subduction of slabs of oceanic lithosphere D) Rebound of the landmass around Hudson Bay after glacial ice sheets have retreated

Q: A mountain range with peaks as high as 14,000 feet above sea level has formed. As time passes, erosion wears down the mountains. How will isostacy affect the crust? A) The surrounding landscape will sink B) The mountain range will rise C) The mountain range will be depressed D) Nothing will change the elevation of the area

Q: ________ is the process by which thickened crust adjusts over time to a "normal" thickness. A) Subduction B) Convection C) Accretion D) Isostacy

Q: Which of the following best explains why some fault-block mountains have an elevated topography? A) Thinning of the lithosphere resulted in upwelling of hot mantle rock and greater lithospheric buoyancy B) Large volumes of rock were thrust on top of the area C) Flood basalts stacked up in the region D) Subduction folded and uplifted the mountain ranges to extensive heights

Q: Which orogeny is largely responsible for creating the modern Rocky Mountains? A) Nevadan Orogeny B) Taconic Orogeny C) Laramide Orogeny D) Alleghanian Orogeny

Q: Which of the following best describes the formation of the Ural Mountains of Russia? A) Marine sediments that had collected in a basin were compressed and uplifted as the former Asian and European plates merged B) Marine sediments were sheared along a transform boundary between the Eurasian and African plates C) A continental volcanic arc formed as two microcontinents collided and subducted D) The landscape was pulled apart by rifting and flood basalts piled up on the landscape

Q: Which U.S. region is made up of a series of high-angle normal faults producing nearly parallel mountain ranges? A) Appalachian Mountains B) Basin and Range Province C) Colorado Plateau D) Valley and Ridge Province

Q: What kind of stress is responsible for creating fault-block mountains? A) Compression B) Tension C) Shear

Q: What are fault-block mountains? A) Mountains formed through folding and thrusting of the crust B) Mountains consisting of exposed batholiths C) Mountains that form by erosion of streams D) Mountains formed through crustal extension and normal faulting

Q: Which of the following statements best characterizes the geology of western North America, starting in California and extending through British Columbia and up into Alaska? A) Divergent rifting creating deep, wide valleys with grabens B) Collision of a massive subcontinent of old igneous and metamorphic rocks, resulting in fold-and-thrust mountains that are still growing C) Geologically distinct, microcontinent-sized fragments and terraces accreted to the continent D) Metamorphosed accretionary wedges

Q: Which of the following describes the events of the Acadian Orogeny? A) Closing of the marginal sea caused a volcanic arc to be thrust over the continent B) North America collided with a microcontinent as the marginal sea continued to close C) The sea along North America closed completely as Africa collided with North America D) The rifting of Pangaea opened the modern Atlantic Ocean

Q: Which of the following describes the events of the Taconic Orogeny? A) Closing of the marginal sea caused a volcanic arc to be thrust over the continent B) North America collided with a microcontinent as the marginal sea continued to close C) The sea along North America closed completely as Africa collided with North America D) The rifting of Pangaea opened the modern Atlantic Ocean

Q: Put the three orogenic events of the Appalachian in order from oldest to youngest. A) Taconic Orogeny, Laramide Orogeny, Acadian Orogeny B) Alleghanian Orogeny, Taconic Orogeny, Acadian Orogeny C) Taconic Orogeny, Acadian Orogeny, Alleghanian Orogeny D) Laramide Orogeny, Taconic, Alleghanian Orogeny

Q: The ________ Orogeny is one of three events that formed the modern Appalachian Mountains. A) Taconic B) Laramide C) Tibetan D) Cordilleran

Q: Which of the following statements best characterizes the geology and structure of the Appalachian Mountains? A) Deeply eroded, late Mesozoic upwarping mountains B) Sedimentary strata folded at in the late Paleozoic Era C) Continental volcanic chain along a subduction zone D) Fault-block mountains developed from rifting of North America from Africa

Q: As India is colliding with Asia, the margin of Asia is experiencing significant deformation. What is happening to the rocks that are being deformed? A) They are being subducted into the mantle B) They are being melted to become magma plutons C) They are being displaced to the southeast to make up Southeast Asia D) They are breaking off to form microcontinents

Q: India has been colliding with Asia for roughly 50 million years, a process that has uplifted the Tibetan Plateau. However, although the margin of Asia has been intensely deformed, India has remained largely intact. Why is this the case? A) Asia's margin is composed of soft materials such as shale and sandstone B) There is a mantle plume beneath the Asian continent that softens the plate, permitting deformation C) Asia's rocks are over 2 billion years old and are so dense they are sinking back into the mantle D) Most of India is tough, durable, ancient shield material and is harder than the newer Asian material

Q: Fold-and-thrust belts are the result of ________ stress whereas fault block mountains are the result of ________ stress. A) compressional; tensional B) shear; compressional C) tensional; shear D) shear; tensional

Q: Which mountain range consists of the youngest collisional mountains on Earth? A) Himalayas B) Andes C) Grand Tetons D) Appalachians

Q: What is a suture? A) A landmass accreted to a continent through subduction B) The zone where two continents are welded together C) The region of a mid-ocean ridge where it is bisected by a transform boundary D) A fold-and-thrust belt created through convergence

Q: Which of the following locations is composed largely of accreted terranes? A) Illinois B) Hawaii C) California D) Colorado

Q: A ________ is a crustal fragment that has been transported by plate tectonics and has adhered to an overriding plate. A) Terrain B) Guyot C) Xenolith D) Terrane

Q: Which type of volcanic material will dominate the eruptions along a continental volcanic arc? A) Mafic lavas B) Lavas of intermediate or felsic composition C) A mix of felsic and ultramafic lavas D) Felsic lavas

Q: What is an accretionary wedge? A) Deformed and thrust-faulted continental lithosphere B) A fan of sediments at the bottom of a deep-ocean trench C) Sediments and ocean crust fragments being scraped off of a subducting plate D) Fault blocks that are slipping down due to extension in a back-arc basin

Q: In what ways are the Sierra Nevada Mountains and the Andes Mountains the same in terms of mountain formation? A) Crumpling of the continent through collision with another continent B) Emplacement of batholiths C) Extension of the continent through rifting D) Downwarping of the continent due to crustal subsidence

Q: How can subduction result in the emplacement of batholiths? A) Partial melting of the mantle overlying the subducting plate creates magma. B) Decompression melting of the plate creates magma. C) Friction of descending plate creates magma. D) Pillow basalts get subducted with plate and forced into overriding plate.

Q: Which of the following locations is a remnant of a forearc basin? A) Death Valley, CA B) Lake Baikal, Siberia C) Snake River Plain, ID D) Great Valley, CA

Q: Which style of convergent boundary will characterize an Andean-type mountain building event? A) Where oceanic lithosphere subducts beneath oceanic lithosphere B) Where continental lithosphere subducts beneath continental lithosphere C) Where oceanic lithosphere subducts beneath continental lithosphere D) Where continental lithosphere subducts beneath oceanic lithosphere

Q: Accretionary wedges will form along a(n) ________ tectonic boundary. A) Convergent B) Divergent C) Transform

Q: ________ will form as sediment collects between the accretionary wedge and the volcanic arc. A) Deep-ocean trench B) Continental shelf C) Back-arc basin D) Forearc basin

Q: ________ is the driving force in orogenesis. A) Extension B) Convection C) Temperature D) Subduction

Q: Which of the following is an example of a volcanic island arc? A) Cascade Volcanoes B) Andean Volcanoes C) Hawaiian Volcanoes D) Aleutian Volcanoes

Q: Which of the following is an example of a continental volcanic arc? A) Cascade Volcanoes B) Hawaiian Volcanoes C) Aleutian Volcanoes D) Icelandic Volcanoes

Q: If a back-arc basin is a region related to a subduction zone, how can such an extensional basin form near a boundary defined by compression? A) Trench rolls back as the old, dense subducting plate sinks. B) Compression ceases before extension takes over. C) Rising magma is softening the crust, allowing it to stretch. D) A plate subducting at an extremely shallow angle is pushing against the back-arc region.

Q: If a back-arc basin is associated with a volcanic island arc, what tends to develop there? A) Submarine trench B) Wide continental shelf C) Long, linear sea D) Rift valley

Q: What is the source of the sediments in a forearc basin? A) Carbonate reefs B) Continental sediments and pyroclastic materials C) Sediments washed from the landmass D) Glacial sediments

Q: How does the angle of subduction affect the dimensions of the forearc basin? A) Shallow angle of subduction leads to a wide forearc basin B) Steep angle of subduction leads to a narrow forearc basin C) Steep angle of subduction leads to a wide forearc basin D) Shallow angle of subduction closes the forearc basin

Q: The Cascadia subduction zone off the coast of Washington and Oregon famously lacks a well-defined deep-ocean trench. Why might this be the case? A) Compression from the convergent boundary has squeezed any potential trench closed. B) There is a massive amount of sediment fill from the Columbia River basin. C) The descending plate is warm and buoyant, so it subducts shallowly. D) There is a shallow angle of plate subduction, as well as large quantities of sediment infill.

Q: Which factor(s) will most influence the depth of deep-ocean trenches? A) Compressive force B) Rate of convection C) Density and composition of the mantle beneath D) Temperature and density of the plate

Q: What are the four regions of a subduction zone? A) Tensional, compressional, shear, convection B) Oceanic, volcanic, continental, island C) Volcanic arc, deep-ocean trench, forearc, and back-arc D) Accretionary wedge, terrane, accumulation zone, submarine canyon

Q: Put the four regions of a subduction zone in order from the convergent boundary landward toward the continental interior. A) Volcanic arc, deep-ocean trench, forearc region, back-arc region B) Back-arc region, volcanic arc, forearc, deep-ocean trench C) Deep-ocean trench, forearc region, volcanic arc, back-arc region D) Forearc, back-arc, deep-ocean trench, volcanic arc

Q: Which of the following regions of a subduction zone are characterized by thick sequences of relatively undeformed sedimentary rocks? A) Volcanic island arc B) Forearc region C) Suture D) Transform fault

Q: ________ contain large quantities of preexisting sedimentary and crystalline rocks that have been faulted and contorted into a series of folds. A) Fault block mountains B) Mid-ocean ridges C) Compressional mountains D) Submarine trenches

Q: In which location on a continent would one be likely to find young mountain belts (less than 100 million years old)? A) In the center of the continent B) On the continental shield C) On the stable platform D) Along the margins of the continent

Q: The American Cordillera is location from ________. A) Maine to Canada B) Cape Horn to Alaska C) Georgia to Newfoundland D) Texas to Arizona

Q: According to the plate tectonics model, most global mountain ranges are associated with which kind of plate boundary? A) Divergent B) Convergent C) Transform

Q: Most mountain ranges are the result of ________ stress. A) Compressional B) Tensional C) Shear

Q: What is the definition of orogenesis? A) Subduction of an oceanic plate beneath a continental plate B) Ionic exchange between calcium and oxygen C) Emplacement of metallic ores via hydrothermal metamorphism D) Processes that collectively form a mountain belt

Q: How do researchers today routinely determine the depth of the water to the seafloor? A) Ship-mounted gravimeters B) A weighted roped or cable C) High-resolution multibeam instruments D) Laser reflector systems linked to satellites

Q: Which of the following groups contains all three major topographic provinces oceanographers use to define the seafloor? A) Continental margins, mid-ocean ridges, and deep-ocean basins B) Mid-ocean ridges, continental shelves, and divergent boundaries C) Submarine trenches, mid-ocean ridges, and turbidity currents D) Deep-ocean basins, active margins, and passive margins

Q: The Challenger Deep has previously been measured to have a depth of 10,994 meters. You have been sent to the part of the Pacific Ocean to verify this depth with an echo sounder. Assuming that Depth = 1/2 (1,500 m/sec*echo travel time), approximately how many seconds should it take for the sound wave to leave your ship, strike the bottom of the Challenger Deep, and return if the depth is correct? A) 10.5 seconds B) 14.66 seconds C) 17.39 seconds D) 22.67 seconds

Q: What is the speed of sound waves in water? A) 1,500 m/sec B) 5,000 m/sec C) 3,200 m/sec D) 10,994 m/sec

Q: The measurement of ocean depth and the topography of the ocean floor are known as ________. A) geophysics B) seismic tomography C) topographic surveying D) bathymetry

Q: Which ship was involved in the first global, comprehensive study of the Earth's oceans starting in 1872? A) U.S.S. Cyclops B) H.M.S. Challenger C) R.M.S. Titanic D) The Glomar Explorer

Q: What feature is present in this image? A) Black smoker B) Coral C) Seamount D) Guyot

Q: What is the name the physical feature in this diagram, marked with an arrow? A) Submarine canyon B) Deep-ocean basins C) Abyssal plains D) Rift valley

Q: What submarine oceanic features are circled in this image? A) Seamounts B) Deep-sea fans C) Rift zones D) Faults

Q: What feature in this image is indicated with arrow X? (Note: it is made of sediments.) A) Deep-sea fan B) Accretionary wedge C) Turbidity current D) Deep-ocean trench

Q: Give a location of where one might find the continental margin in this image. A) Off the coast of southern California B) Eastern margin of North America C) Western margin of South America D) Northern margin of North America

Q: What kind of continental margin is visible in this image? A) Active B) Rift C) Passive D) Transform

Q: Which location possesses the continental margin in this image? A) Western margin of South America B) Eastern margin of North America C) East of Japan D) Around the Philippines

Q: What kind of continental margin is visible in this image? A) Active B) Rift C) Passive D) Transform

Q: Based on the seafloor features labeled on this map, what kind of tectonic boundary would you say surrounds the Pacific Ocean basin? A) Convergent B) Divergent C) Transform

Q: Assume the Mid-Continental Rift were to reactivate and divergence were to occur. What sequence of events would unfold as rifting began and what would eventually happen to the landmass?

Q: Discuss how oceanic crust forms. What process generates the necessary magma? Also, be sure to discuss ophiolite sequences and discuss how the formation of each layer contributes to the formation of the crust.

Q: Oceanic Ridge A has slow spreading rates of 2-5 cm/yr. Oceanic Ridge B has intermediate spreading rates of 6-9 cm/yr. Oceanic Ridge C has fast spreading rates of 10-11 cm/yr. Compare and contrast the topography and structure that would be present at all three spreading centers.