Q&A Hero

Q: Compare seamounts and guyots. How do the two features differ?

Q: Compare and contrast the formation of accretionary wedges and the process of subduction erosion.

Q: Explain the process of accretionary wedge.

Q: How are sound waves used to detail the shape of the seafloor?

Q: Put the layers of an ophiolite complex in order from top to bottom: A) Gabbro B) Deep-sea sediments or sedimentary rocks C) Sheeted dike complex D) Pillow basalts 1. Layer 1 (Uppermost layer) 2. Layer 2 3. Layer 3 4. Layer 4 (Lowermost layer)

Q: Match the seafloor terms to their correct definitions. A) Flat seafloor in the deep ocean B) Wedge of sediments deposited by turbidity currents that formed at the base of the slope C) Narrow creases in the seafloor that result from subduction D) Gently sloping, submerged extension of the continent E) A steep incline that marks the boundary between the continental crust and the oceanic crust 1. Continental shelf 2. Abyssal plain 3. Submarine trench 4. Continental rise 5. Continental slope

Q: Why does the lithosphere thicken as it moves away from a mid-ocean ridge?

Q: Why are oceanic ridges elevated above the rest of the seafloor?

Q: Describe the appearance of a rift valley that has started on land. How do these valleys form?

Q: Why does the Atlantic Ocean have the most extensive abyssal plains?

Q: What three major features comprise a passive continental margin?

Q: Black smokers can be found along subduction zones.

Q: Based on its slow rate of spreading, the East Pacific Rise has a gradual profile with gently sloping sides.

Q: Oceanic ridges form as a result of compressional stress.

Q: Oceanic plateaus form from turbidity currents that flow down the continental slope.

Q: Abyssal plains are flat areas of the ocean floor that are likely the most level places on Earth.

Q: Continental shelves are valuable locations that support important fishing grounds.

Q: Continental shelves on active margins are larger and broader than those on passive margins.

Q: A passive continental margin is located hundreds of miles away from the nearest tectonic boundary.

Q: Because massive submarine structures such as seamounts and ridges exert stronger than average gravitational attraction, they produce depressed areas on the ocean's surface.

Q: The Challenger Deep of the Mariana Trench is named for the H.M.S Challenger, the ship that first measured it.

Q: What happened when the spreading center that generated the Farallon plate collided with the North American plate?A) A mantle plume formed.B) A divergent plate boundary was created.C) The spreading center subducted, resulting in the Yellowstone Hot Spot.D) A transform boundary was created.

Q: Which of the following locations is an example of spontaneous subduction? A) Mariana Trench B) Peru-Chile Trench C) East African Rift D) Cascadia Trench

Q: Which of the following locations is an example of forced subduction? A) Mariana Trench B) Peru-Chile Trench C) East African Rift D) Mid-Atlantic Rift

Q: What kind of subduction occurs when younger, warmer, less-dense lithosphere dips under another plate at shallower angles because it is too buoyant to sink? A) Forced subduction B) Mantle plume subduction C) Spontaneous subduction D) Overriding subduction

Q: What kind of subduction occurs when old, dense lithosphere sinks into the mantle by its own weight rather than by compressional force? A) Forced subduction B) Mantle plume subduction C) Spontaneous subduction D) Overriding subduction

Q: What is the name of the supercontinent that preceded Pangaea? A) Amasia B) Rodinia C) Challenger D) Africana

Q: Which of the following locations displays a triple junction that resulted from a rising mantle plume? A) Eastern Africa/Arabian Peninsula B) East Pacific Rise C) Japan/East Asia D) Mid-Atlantic Ridge

Q: Which of the following is a failed rift that formed in North America over one billion years ago? A) A Mid-Continent Rift B) East African Rift C) Chile Rise D) Kuril Trench

Q: A ________ forms when a rising mantle plume causes the overlying crust to dome and separate into three rifts. A) triple junction B) complex rift C) submarine canyon system D) divergent boundary

Q: Why do mantle plumes tend to concentrate beneath supercontinents such as Pangaea? A) Concentrations of radioactive materials build up as continents assemble. B) Partial melting from subduction concentrates large volumes of magma. C) A large landmass acts as an insulating blanket to trap heat in the mantle. D) Friction from converging landmasses heats up the mantle.

Q: Which of the following is not a possible mechanism contributing to continental rifting? A) Changes in gravitational attraction of the moon B) Concentration of mantle plume heat beneath a continent C) Tensional stress D) Upwelling from shallow levels in the asthenosphere

Q: Which process, common near black smokers, will use hot water circulating through the crust to alter olivine and pyroxene into chlorite and serpentine? A) Hydrothermal metamorphism B) Decompression melting C) Partial melting D) Thermal contraction

Q: Thermal springs known as ________ are often associated with oceanic ridges, where hot water containing dissolved minerals gushes from the seafloor. A) hot springs B) geysers C) black smokers D) ophiolites

Q: A(n) ________ is a sequence of layers composing the oceanic crust that includes sheeted dikes, basalts, and gabbro. A) passive margin B) ophiolite complex C) lithospheric sheeting D) flood basalts

Q: Which of the following is not an example of a continental rift? A) East Africa B) Rhine Valley, Europe C) Lake Baikal, Siberia D) Appalachia, United States

Q: What is the average thickness of the oceanic crust? A) 0 km B) 3 km C) 7 km D) 20 km

Q: The oceanic crust is composed almost entirely of ________ rocks that are underlain by ________ rocks, which makes up the lithospheric mantle. A) felsic; sediments B) intermediate; felsic C) sedimentary; mafic D) mafic; ultramafic

Q: Which of the following choices represents a rate of seafloor spreading commonly associated with a ridge such as the Mid-Atlantic Ridge? A) 1-5 mm/yr B) 1-5 cm/yr C) 1-5 m/yr D) 1-5 km/yr

Q: Which of the following materials or features are not found at mid-ocean ridges? A) Basaltic lava eruptions emitted along the ridge B) Stands higher above the surrounding seafloor C) Deep submarine trenches D) Thin layers of sediments

Q: What generates the magma necessary for seafloor spreading? A) Decompression melting B) Partial melting C) Mantle plumes D) Subduction

Q: ________ accounts for greater ocean depths moving away from the oceanic ridge toward the deep ocean basin. A) Mantle plume B) Convection C) Thermal contraction D) Gravity

Q: What rock would you expect to find associated with a mid-ocean ridge? A) Sandstone B) Granite C) Limestone D) Basalt

Q: Which of the following is an example of a mid-ocean ridge? A) Puerto-Rico Trench B) Challenger Deep C) Mid-Indian Ridge D) East Pacific Rise

Q: Where do rift valleys form along the oceanic ridge system? A) Along the flanks of the continent where the slope levels out to meet the seafloor B) Along the axis of some ridge segments where the rift is down-faulted C) Transecting the ridge where transform boundaries exist D) Where the seafloor plunges back into the mantle as the plate is consumed

Q: Which of the following is not a method of obtaining samples and observations of the oceanic ridge system? A) Finding segments of ocean floor that have been thrust up onto the continent B) Visual inspections using submersible equipment C) Deep sea core samples D) Side-scan sonar

Q: Volcanic islands such as the Hawaiian islands form as a result of ________. A) subduction B) rifting C) mantle plumes D) batholith emplacement

Q: What is the source of flood basalts associated with oceanic plateaus? A) Decompression melting associated with seafloor spreading B) Partial melting associated with subduction C) Impact heating from a meteorite strike D) The melting of the head of a mantle plume

Q: How do deep-ocean trenches form? A) Magma from a partially melting tectonic plate makes its way through the crust. B) Subducting lithosphere descends into the mantle. C) Two tectonic plates diverge and create a rift valley. D) Sediments from a turbidity current settle out in a deep ocean basin.

Q: Volcanic island arcs are found near which features on the seafloor? A) Abyssal plains B) Coral atolls C) Deep-ocean trenches D) Rift zones

Q: Approximately what percentage of the Earth's surface consists of deep-ocean basins? A) 10% B) 30% C) 47% D) 49%

Q: Along which tectonic boundary are deep-ocean trenches found? A) Convergent B) Divergent C) Transform

Q: Where is the deepest place on Earth? A) Peru-Chile Trench B) Challenger Deep C) Kuril Trench D) Mid-Continent Rift

Q: What is the definition of subduction erosion? A) Sediments from the ocean floor are scraped off a subducting tectonic plate and adhere to the overriding plate. B) Diverging tectonic plates will cause rocks to slide downward along normal faults. C) Glaciers extending off the continent will scour deep grooves in continental shelves. D) Sediment and rock are scraped off the bottom of an overriding plate and transported into the mantle by a descending plate.

Q: A(n) ________ forms when sediments from the ocean floor and pieces of oceanic crust are scraped from a subducting oceanic plate and adhere to an overriding tectonic plate. A) accretionary wedge B) deep-sea fan C) active tectonic margin D) submarine canyon

Q: Submarine canyons found cutting into the continental shelf and slope are believed to have been created ________. A) by subduction B) by icebergs C) by rivers during the ice age D) by tectonic rifting

Q: Which part of a passive continental margin is built up by repeated deposition from turbidity currents? A) Abyssal plain B) Continental shelf C) Continental slope D) Continental rise

Q: What is the definition of a turbidity current? A) Subsidence of the seafloor B) Fast-moving water created by density differences C) Submarine landslide D) Focused jet of water blasting across the shelf from a surface stream

Q: Which of the following will mark the furthest extent of a continent? A) The shoreline B) Tidal flats exposed during low tide C) The crest of the continental slope D) The lowest part of the continental slope

Q: Although many areas of the continental shelves are relatively featureless, there are some locations on the shelves that have received extensive glacial deposits and significant dissection by streams. How would this have been possible? A) Glaciers and streams were powerful enough to shape the shelf underwater. B) The shelves were once above sea level but have since dropped below sea level due to tectonic activity. C) The sea level dropped during the last glacial episode because water was stored in large ice sheets, exposing the shelves. D) As the continents collided in the past, the shelves were lifted above sea level and became exposed to the elements.

Q: The continental shelf is composed of which material(s)? A) Granitic crust covered with sedimentary rocks B) Basaltic crust C) Clay sediments and sands D) Ophiolites

Q: Which of the following scenarios would likely result in the development of a passive continental margin? A) Two tectonic plates colliding, creating a submarine trench B) Continental blocks rifting apart and becoming separated by seafloor spreading C) Two tectonic plates sliding past each other, rotating part of the crust D) A mantle plume creating a chain of volcanic islands across the seafloor

Q: Which region is surrounded by an active continental margin? A) Atlantic Ocean B) Arctic Ocean C) Pacific Ocean D) Indian Ocean

Q: Which of the following is associated with a passive continental margin? A) Divergent boundaries B) Convergent boundaries C) Transform boundaries D) No tectonic boundaries nearby

Q: Which of the following is associated with an active continental margin? A) Divergent boundaries B) Convergent boundaries C) Transform boundaries D) No tectonic boundaries nearby

Q: What are the two types of continental margins? A) Transform and divergent B) Trenches and rifts C) Continental shelves and slopes D) Passive and active

Q: What tool is often used to measure the topography of the seafloor today? A) High-resolution multibeam instruments B) Sonar C) Echo sounders D) Radar altimeters

Q: This seismic tomographic slice of Earth indicates the variations in S-wave speeds through the interior. Through which region will S waves move the fastest? A) Pacific Ocean B) Farallon plate C) Mid-Atlantic Ridge D) Africa

Q: Which of the following is a negative gravity anomaly on this map? A) Location A B) Location B C) Location C D) Location D

Q: Which of the following is a positive gravity anomaly on this map? A) Location A B) Location B C) Location C D) Location D

Q: Which of these four images would accurately demonstrate the path seismic rays would take through the interior if the interior of Earth was made of uniform materials? A) B) C) D)

Q: What seismic shadowing zone is visible in this image? A) P-wave shadow B) S-wave shadow C) Surface wave shadow D) Seismic ray shadow

Q: Which section (A, B, or C) indicates the zone where refracted seismic waves are received? A) Section A B) Section B C) Section C

Q: Which section (A, B, or C) indicates the zone where direct seismic waves are received? A) Section A B) Section B C) Section C

Q: Which section (A, B, or C) shows the P-wave shadow zone? A) Section A B) Section B C) Section C

Q: What seismic shadowing is visible in this image? A) P-wave shadow B) S-wave shadow C) Surface wave shadow D) Seismic ray shadow

Q: This figure shows what will happen as a seismic wave moves from a material of one density to a material of a different density. Indicate which rock is a high or low density material by matching the correct choice to the correct material based on the refraction of the seismic wave. A) High density material B) Low density material 1. A 2. B

Q: This figure shows what will happen as a seismic wave moves from a material of one density to a material of a different density. Indicate which rock is a high or low density material by matching the correct choice to the correct material based on the refraction of the seismic wave. A) Low density material B) High density material 1. A 2. B

Q: What is the definition of a dipolar field?

Q: What are the three main mechanisms of convective flow in the outer core?