Geology 100 Chapters 10 and 11

B. abyssal plain next to the continents

In the Atlantic Ocean, where is the oldest oceanic crust? A. mid-ocean ridges B. abyssal plain next to the continents C. oceanic trenches D. seamounts E. continental shelves close to the shoreline

B. oceanic crust older than 180 million years has been subducted and the record destroyed

Seafloor spreading rates cannot be used to reconstruct past continents' positions older than 180 million years. Why? A. no magnetic reversals occurred before 180 million years ago B. oceanic crust older than 180 million years has been subducted and the record destroyed C. continents only started changing positions 180 million years ago D. nobody knows

C.

The basin shown in this figure was actively subsiding during the formation of unit: basin.png A B C D E

D. all of the above

What are some uses of magnetic reversals? A. matching the patterns of reversals in a rock sequence to the magnetic time scale B. studying magnetic stripes on the seafloor C. calculating rates of seafloor spreading D. all of the above E. a and b only

C. formation of rifts that radiate out from the hot spot

What can occur during the evolution of a hot spot? A. an initial period of subsidence as magmas rise from the mantle B. formation of a fold and thrust belt C. formation of rifts that radiate out from the hot spot D. thickening of the crust beneath a passive margin E. none of the above

E. a and b only

What causes the seafloor to deepen across a typical continental slope? A. thinning of continental crust because of normal faults B. a transition from continental crust to oceanic crust C. down flexing of oceanic crust because of subduction D. deposition of sediment from turbidity currents E. a and b only

B. less dense continental crust

What could cause a region to be higher in elevation than an average part of a continent? a. thinner continental crust b. less dense continental crust c. cooler continental crust d. crust that has been horizontally stretched e. a and b only

C. it became smaller as the Atlantic Ocean opened

What has happened to the Pacific Ocean in the last 200 million years? A. it has become deeper as the rate of seafloor spreading increased B. it became wider because of seafloor spreading C. it became smaller as the Atlantic Ocean opened D. it remained unchanged in size E. none of the above

C. a volcanic island forms and subsides

What is a popular model for the formation of an atoll? A. a moderate-sized meteoroid forms a circular crater on the seafloor B. a volcanic eruption forms a large circular caldera C. a volcanic island forms and subsides D. a barrier reef becomes buried by volcanic eruptions

D. parts of the continent have been added by the accretion of tectonic terranes

What is the main reason why the age of oldest rocks can vary from one part of a continent to another? A. older rocks are commonly remelted over huge regions B. older rocks have been uplifted and eroded away C. large parts of the continent are subducted deep within the mantle D. parts of the continent have been added by the accretion of tectonic terranes

E. a and b only

Which of the following processes forms basins in an ocean-continent convergent boundary? a. flexing and bending of the oceanic plate into the subduction zone b. flexing of the continent by weight of the thrust sheets c. thinning of the lithosphere above the subduction zone d. thickening of the crust by magmas from the subduction zone e. a and b only

D. all of the above

How can we tell that the Himalaya have been uplifted? a. uplift can be measured with a global positioning system (GPS) b. deep rocks are exposed at the surface and yield young isotopic ages c. the top of Mount Everest contains a limestone with marine fossils d. all of the above e. a and b only

C. they are constructed by volcanic eruptions that first occur under water

How do most oceanic islands and seamounts form? A. they are small pieces rifted apart from continents B. they are places where the seafloor has been buckled upward by convergence C. they are constructed by volcanic eruptions that first occur under water D. they are large fan-shaped mounds deposited by turbidity currents

D. large amounts of basalt derived from melting in the mantle

If you drilled into an oceanic plateau, what would you most likely find? A. a thin layer of oceanic sediment over continental crust B. andesitic volcanoes buried by turbidity currents C. a normal thickness of oceanic crust overlain by andesitic volcanoes D. large amounts of basalt derived from melting in the mantle

D. in a submarine fan

If you were looking for graded beds, where would be a good place to start? A. in a warm and shallow lagoon B. in the center of an atoll C. just offshore of a sediment-poor beach D. in a submarine fan E. none of the above

E. a and b only

What processes can occur in front of or behind some island arcs? A. trench rollback B. back-arc rifting C. fold and thrust belts in the mountains D. formation of an oceanic plateau E. a and b only

D. passive margin

Which of the following is NOT a setting in which regional mountain belts form? A. continental collision B. subduction zone C. upwelling of the mantle D. passive margin E. the collision of India with Asia

E. all of the above are ways to make local moutains

Which of the following is NOT a way in which local mountains can be built? A. prolonged volcanism in composite volcanoes B. thrust faulting C. normal faulting D. folding E. all of the above are ways to make local mountains

D. all of the above

Which of the following occurs when mountain belts are eroded? a. erosion is accompanied by isostatic rebound b. the continental crust becomes thinner c. deep metamorphic and plutonic rocks can be uplifted to the surface d. all of the above e. a and b only

E. both a and b

Why are the patterns showing the age of the seafloor symmetrical in the Atlantic Ocean but not the Pacific Ocean? A. spreading along the Atlantic ridge added seafloor to plates on both sides B. subduction has consumed large areas of old oceanic crust in the Pacific C. subduction has consumed large areas of old oceanic crust in the Atlantic D. none of the above E. both a and b