Chapter 2 Plate Tectonics

During what time period did scientists first notice the jigsaw puzzle fit of the southern continents? A) 1600s B) 1750s C) 1800s D) 1910s

A) 1600s

Which of the following statements best describes the tectonic setting for Mount St. Helens and the other Cascade volcanoes? A) A chain of young, active volcanoes built on a continental margin above a sinking slab of oceanic lithosphere B) A chain of old, inactive volcanoes built while western North America moved over a mantle plume C) Old, deeply eroded volcanoes built before the Pacific Ocean existed D) Young, deeply eroded, basaltic volcanoes built when western North America was over the present-day site of the Hawaiian hot spot

A) A chain of young, active volcanoes built on a continental margin above a sinking slab of oceanic lithosphere

Where is the top of the asthenosphere closest to Earth's surface? A) Along a mid-ocean ridge B) Above a deep mantle plume C) Along a transform fault D) Along a subduction zone

A) Along a mid-ocean ridge

The ________ is a hotter, weaker region in the mantle that lies below the lithosphere and responds to forces by flowing. A) asthenosphere B) outer core C) inner core D) atmosphere E) crust

A) Asthenosphere

What is slab pull? A) Cold oceanic lithosphere is pulled below warmer asthenosphere. B) Cold continental lithosphere is pulled below warmer asthenosphere. C) Cold continental lithosphere is pulled below warmer oceanic lithosphere. D) Warmer oceanic lithosphere is pulled below colder asthenosphere.

A) Cold oceanic lithosphere is pulled below warmer asthenosphere.

Which of the following is not one of the major tectonic plates on the Earth's surface? A) Juan de Fuca Plate B) North American Plate C) African Plate D) Pacific Plate

A) Juan de Fuca Plate

Which model of convection describes how the interior is divided into several levels of convection cells? A) Layer cake model B) Whole-mantle convection C) Plume model D) Differentiation model

A) Layer cake model

Which type of convergence will result in a continental volcanic arc? A) Oceanic-continental B) Oceanic-oceanic C) Continental-continental

A) Oceanic-continental

Which type of convergence will result in a volcanic island arc? A) Oceanic-continental B) Oceanic-oceanic C) Continental-continental

A) Oceanic-continental

Think about what happens to the density of an oceanic plate as it ages and cools. How will the age and temperature of the subducting plate affect its angle of descent? A) Old, cool plates will have a shallow angle of descent. B) Old, warm plates will have a steeper angle of descent. C) Young, warm plates will have a shallow angle of descent. D) Young, cool plates will have a steeper angle of descent.

A) Old, cool plates will have a shallow angle of descent.

What is the name of the supercontinent proposed by Alfred Wegener? A) Pangaea B) Rodinia C) Amasia D) Nuna

A) Pangaea

Which of the following makes it possible for oceanic crust created at divergent boundaries to be carried to the sites of destruction at convergent boundaries? A) Transform boundaries that accommodate plate motion B) Seawater seeping into plate fractures to lubricate the rocks C) Magma plutons weighing the crust down at convergent boundaries, pulling the slab D) Alignment of magnetic fields in iron particles

A) Transform boundaries that accommodate plate motion

All of the following offer additional evidence supporting the theory of plate tectonics except for ________. A) changes in the Moon's orbit due to shifting plates B) ocean floor sediment cores C) hot spots D) measurements of plate motions

A) changes in the Moon's orbit due to shifting plates

Another name for a ________ boundary is a destructive boundary. A) convergent B) divergent C) transform

A) convergent

At a ________, an oceanic plate will be forced beneath another plate because of differences in density. A) subduction zone B) continental rift C) transform boundary D) collision zone

A) subduction zone

Which is denser: a 100-million-year-old oceanic lithosphere near a convergent boundary, a 15-million-year-old oceanic lithosphere near a rift, or the upper part of the asthenosphere? A) A 15-million-year-old oceanic lithosphere B) 100-million-year-old oceanic lithosphere C) Upper asthenosphere D) They all have the same density.

B) 100-million-year-old oceanic lithosphere

In which decade was the theory of plate tectonics developed? A) 1940s B) 1960s C) 1970s D) 1990s

B) 1960s

When the continents were assembled and mountain ranges were matched up, mountains in Scandinavia and the British Isles matched up perfectly with which North American mountain range? A) Rocky Mountains B) Appalachian Mountains C) Sierra Nevada Mountains D) Olympic Mountains

B) Appalachian Mountains

What two pieces of information would researchers need to have in order to calculate the rate of plate motion for seafloor spreading? A) Age of the continent and depth of the water B) Distance from the rift and age of seafloor sample C) Age of the seafloor sample and age of the continent D) Type of rock and distance from the rift

B) Distance from the rift and age of seafloor sample

Along which tectonic boundary is ridge push going to be most important in helping to drive plate motion? A) Convergent boundary B) Divergent boundary C) Transform boundary

B) Divergent boundary

Where is oceanic lithosphere thickest and why? A) Along oceanic ridges because it is newest there B) Furthest from the spreading center because the older oceanic crust is cooler C) In the middle of the tectonic plate as it has not been scraped off during subduction D) Close to the subduction zone boundary because continental material is added to it

B) Furthest from the spreading center because the older oceanic crust is cooler

In which layer of the Earth does the convection necessary for plate motion occur? A) Crust B) Mantle C) Outer core D) Inner core

B) Mantle

Where are the majority of transform faults located? A) Southern California B) On the ocean floor offsetting segments of oceanic ridge C) Radiating from convergent boundaries as stress fractures D) Along mountain ranges that have been thrust up due to collision

B) On the ocean floor offsetting segments of oceanic ridge

________ occurs when magnetic minerals in lavas align their magnetic fields with magnetic north, preserving a record of that pole's location at that moment in time. A) A mantle plume B) Paleomagnetism C) Magnetic reversal D) Seafloor spreading

B) Paleomagnetism

________ is the name of the process by which new seafloor is generated at mid-ocean ridges. A) Subduction B) Seafloor spreading C) Convection D) Melting

B) Seafloor spreading

Which two continents did Wegener cite as having the best evidence of a close coastline fit? A) North America and Europe B) South America and Africa C) Europe and Africa D) India and Asia

B) South America and Africa

Why are the mid-ocean ridges higher in elevation than the surrounding ocean floor? A) The force of magma extruding from the fissure pushes the seafloor up. B) Warmer material near the ridge is less dense, so it is more buoyant on the mantle. C) The collision of the tectonic plates is forcing material higher. D) Thermal springs developing in stress fractures are depositing large volumes of material, increasing the height.

B) Warmer material near the ridge is less dense, so it is more buoyant on the mantle.

Which war was indirectly responsible for the development of the tools that made the theory of plate tectonics possible? A) World War I B) World War II C) Korean War D) Vietnam War

B) World War II

A ________ is a geographic low, which marks the location where oceanic lithosphere descends into the mantle. A) fold and thrust mountain B) deep-ocean trench C) seismic zone D) mid-ocean rift

B) deep-ocean trench

In the mid-twentieth century, researchers dredging the seafloor could not find any materials older than ________. A) 10,000 years B) 1.2 million years C) 180 million years D) 1.5 billion years

C) 180 million years

When considering evidence of glaciation on the southern continents, why did Wegener reject the explanation that the entire planet had experienced a period of extreme cooling? A) Because the glacial debris was localized to a few small mountain valleys B) Because he knew the "glacial debris" was actually a misinterpreted landslide C) Because geologic evidence supported the existence of tropical swamps in the Northern Hemisphere D) Because the 16O/18O ratios in fossils supported an ice-free period

C) Because geologic evidence supported the existence of tropical swamps in the Northern Hemisphere

Which is least dense? A) Oceanic lithosphere B) Mantle C) Continental lithosphere D) Asthenosphere

C) Continental lithosphere

How can GPS receivers and satellites be used to monitor plate motion? A) GPS receivers are placed on landmasses to track their locations. B) Satellites send lasers to measure the distance to continents. C) GPS receivers send signals to each other to see if the units are getting closer together. D) Satellites track seafloor spreading.

C) GPS receivers send signals to each other to see if the units are getting closer together.

________ and ________ drive water from the pores of a subducted oceanic plate, which leads to partial melting. A) Compression; tension B) Air; heat C) Heat; pressure D) Salt; oil

C) Heat; pressure

In the whole-mantle convection model, what feature balances the deeply descending lithosphere by transporting hot material toward the surface? A) Kimberlites B) Decompression melting C) Mantle plumes D) Rift zones

C) Mantle plumes

Which factor contributes the most toward plate motion at a convergent boundary? A) Ridge push B) Mantle drag C) Slab pull D) Friction

C) Slab pull

Which of the following best explains the global distribution of plant species, such as the Glossopteris, during the Mesozoic? A) Seeds were small, so they could be carried by the wind. B) Seeds were ingested by animals and later deposited in scat. C) The landmasses were joined and the plant had a large geographic extent. D) Oceans that transgressed on the continents carried the seeds to different locations.

C) The landmasses were joined and the plant had a large geographic extent.

Which of the following statements regarding the global oceanic ridge system is correct? A) The ridge system marks the deepest locations on the Earth's surface. B) The ridge system marks the locations of most mantle plumes in the mantle. C) The ridge system is the longest topographic feature on the Earth's surface. D) The ridge system has an extensive submarine canyon system.

C) The ridge system is the longest topographic feature on the Earth's surface.

Which of the following plate boundaries is not usually associated with volcanism? A) Convergent B) Divergent C) Transform

C) Transform

Which type of plate boundary accounts for the smallest percentage of all plate boundaries on the surface of the Earth? A) Convergent boundaries B) Divergent boundaries C) Transform boundaries

C) Transform boundaries

How can the orientation of transform faults provide information about the direction of plate motion? A) Transform faults are oriented perpendicular to the direction of plate motion. B) Transform faults radiate out from the rift zone located in the center. C) Transform faults are parallel to the direction of plate motion. D) Transform faults are parallel to convergent boundaries.

C) Transform faults are parallel to the direction of plate motion.

Although the jigsaw-puzzle fit of the southern continents was noted, opponents of continental drift argued that, even if continental displacement had occurred, a good fit between the continents today would be unlikely. What geologic evidence did they cite to support this claim? A) Deposition in river deltas had changed the longshore current, resulting in erosion. B) The tensional stress of splitting sheared the continents beyond all repair. C) Wave erosion and coastal deposition have changed the shape of the continents. D) Fissure eruptions along continental margins had created new land.

C) Wave erosion and coastal deposition have changed the shape of the continents.

Continental crust is mainly composed of ________, whereas oceanic crust is mainly composed of ________. A) olivine; basalt B) limestone; gabbro C) granite; basalt D) gabbro; granite

C) granite; basalt

A typical rate of seafloor spreading in the Atlantic Ocean is ________. A) 2 meters per year B) 0.1 inches per year C) 20 feet per year D) 2 centimeters per year

D) 2 centimeters per year

Which scientist developed the idea of continental drift? A) Isaac Newton B) Charles Darwin C) Albert Einstein D) Alfred Wegener

D) Alfred Wegener

What is a mantle plume? A) The magma that rises up from the mantle at a divergent plate boundary B) Material rising up from a subducting plate going through partial melting C) A form of batholith composed of ferromagnesian materials D) An upwelling of hot material from the Earth's interior that is cylindrical in shape

D) An upwelling of hot material from the Earth's interior that is cylindrical in shape

What generates the heat necessary for convection in the Earth? A) Volcanic eruptions B) Friction between moving slabs C) Chemical reactions between geologic materials and hydrothermal fluids D) Decay of radioactive materials

D) Decay of radioactive materials

How did researchers in the mid-twentieth century obtain ocean floor samples in order to determine the age of the seafloor? A) Satellite imagine images B) Deep-diving manned submersibles C) Hydraulic vacuum tubes D) Drilling ships

D) Drilling ships

Continental rifting is occurring today in ________. A) western California (San Andreas Fault) B) between Minnesota and Wisconsin (mid-continent rift) C) the Pacific Northwest (Cascadia subduction zone) D) Ethiopia and Kenya (East African Rift valley)

D) Ethiopia and Kenya (East African Rift valley)

Lava solidifying during a period of reverse polarity will align the magnetic fields of its iron particles toward the ________ pole. A) East B) West C) North D) South

D) South

Samples from the seafloor around the Mid-Atlantic Ridge and the East Pacific Rise show that both areas have been creating new material in the last five million years. Samples from the East Pacific Rise show the five-million-year-old seafloor is three times as wide as similarly aged material from the Mid-Atlantic Ridge. What does this say about the rate of seafloor spreading in the East Pacific? A) The seafloor at both sites is growing at the same rate. B) The seafloor at the East Pacific Rise is growing more slowly. C) The seafloor at the Mid-Atlantic is growing more quickly. D) The seafloor at the Mid-Atlantic is growing more slowly.

D) The seafloor at the Mid-Atlantic is growing more slowly.

The lithosphere is composed of the ________ and the rigid part of the ________. A) outer core; inner core B) mantle; outer core C) crust; lower mantle D) crust; upper mantle

D) crust; upper mantle

The lithosphere is broken into ________ major plates and many minor plates. A) seven B) nine C) twelve D) fifteen

D) fifteen

Even before the proposal of continental drift, paleontologists recognized that some sort of land connection was needed to account for the identical fossil organisms found on multiple continents. Select the correct hypothesis or hypotheses these paleontologists developed. A) Sea level falling B) A chain of island stepping stones C) Floating debris used as rafts and sea level rising D) A transoceanic land bridge E) Island stepping stones, transoceanic land bridge, and floating debris used for rafts

E) Island stepping stones, transoceanic land bridge, and floating debris used for rafts

A convergent boundary is usually associated with which physical features? A) Rift valleys B) Volcanic arcs C) Horizontally displaced rocks D) Submarine trenches E) Volcanic arcs and submarine trenches

E) Volcanic arcs and submarine trenches

True or False? Subduction zones will only develop between a continental plate and an oceanic plate.

False

True or False? An oceanic plate that has been permeated by water before subduction will trigger melting sooner than a "dry" oceanic plate.

True

True or False? The magnetic poles roughly correspond to the locations of the geographic poles.

True

True or False? The majority of divergent plate boundaries are associated with oceanic ridges.

True