Geol 107 Exam 2

Asthenosphere Choose one: A. is the lower layer of both continental and oceanic lithosphere. B. subducts when it collides with continental lithosphere. C. is warm enough to flow slowly. D. is the uppermost layer of Earth's core.

C. is warm enough to flow slowly.

Accretionary prisms form due to what process? Choose one: A. rifting B. transform motion C. subduction D. divergence

C. subduction

A "polar wander" curve shows

How continents have moved or drifted relative to the magnetic poles

The largest mountain in the solar system, called Olympus mons, is an enormous shield volcano on

Mars

which layer is the least dense?

Mesosphere

the youngest rocks on the seafloor can be found

Near the mid-ocean ridge

In which earth layer is the magnetic field generated?

Outer core

what makes up the majority of the earths crust?

Oxygen and silicon

An explosive subsea eruption involving a lot of steam and fountains of wet ash is called

Surtseyan

magnetic minerals in a magma

Tend to align themselves to the earths magnetic field as they cool

magnetic minerals in a magma:

Tend to align themselves to the earths magnetic field as they cool

where can the thinest oceanic crust of the sea floor be found the thinnest

by the mid ocean ridge

Limestone reefs and salt deposits are important in the reconstruction of the Earth's history because they

can be used to infer the ancient climate of the Earth; they are deposited in environments that are restricted to warm climates.

in what layer is the magnetic field generated?

in the outer core

what is the composition of the entire earth

iron, oxygen, silicon, and magnesium

Is low viscosity magma thick or thin, and how does it flow?

it is thin and flows like water

Wegener's evidence for a united Pangaea comes from the fossil record of which type of organisms?

land animals

during convergent boundaries, the ______ is subducted back into the earth

lithosphere

what is the composition of the earths crust?

mainly oxygen and silicon

What layer is the least dense?

mesosphere

What is the name given for the boundary between the crust and the mantle

moho

has a rope-like texture identical to that seen in the foreground of the image.

pahoehoe

what are coastlines that coincide with plate boundaries called?

passive margins

Which statement about the plate tectonics is true

satalite data now allow direct measurement

what is the largest layer of the earth?

the mantle

the magnetic dip preserved in a rock indicates:

the rock's magnetic latitude at the time it crystallized

when can a deep trench be formed?

with convergent boundaries

...

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The presence of pillow lava is evidence of which volcanic circumstance? Choose one: A. high-silica-content magma B. an explosive eruption C. a submarine volcano D. caldera formation

C. a submarine volcano

Small, circular piles of basaltic lapilli and volcanic debris are called Choose one: A. craters. B. calderas. C. cinder cones. D. fissures.

C. cinder cones.

Which of the following statements about lithosphere and asthenosphere is true? Choose one: A. Lithosphere consists of the crust and the upper mantle and behaves like a hard layer that breaks and bends. B. Asthenosphere consists of the lower, middle, and upper mantle, and is defined as mantle material that is cooler than 1280°C. C. Lithosphere is more mafic than asthenosphere. D. Lithosphere and asthenosphere have the same physical properties; they are both rigid.

A. Lithosphere consists of the crust and the upper mantle and behaves like a hard layer that breaks and bends.

Which of the following is considered a warning sign of imminent eruption? Choose one: A. change in heat flow from the volcano's surface B. decreased gas emissions and hydrothermal activities C. a period of quiescence in the volcano's activity D. decreased earthquake activity

A. change in heat flow from the volcano's surface

Continents Choose one: A. passively ride along as the sea floor spreads. B. have retained the same size and shape throughout Earth's history. C. may subduct if they are old and dense enough. D. plow their way through the sea floor.

A. passively ride along as the sea floor spreads.

The global occurrence of earthquakes reveals that Choose one: A. they usually occur on the boundaries of plates or at hot spots. B. their locations are randomly scattered. C. they prove that Earth is splitting apart (rifting) at all plate boundaries. D. they usually occur at the center of plates.

A. they usually occur on the boundaries of plates or at hot spots.

Earthquakes but not volcanoes occur in San Francisco because Choose one: A. two plates are moving past each other there. B. an oceanic plate is converging with a continental plate and subducting there. C. a continental plate is colliding with another continental plate there. D. two plates are diverging there.

A. two plates are moving past each other there.

sediments that are scraped off of a subducting slab combine to for a

Accretionary prism

sediments that are scraped off of a subducting slab combine to form a

Accretionary prism

Who's theory was Continental Drift?

Alfred Wegener

The Himalayas are growing because Choose one: A. two plates are diverging there. B. a continental plate is colliding with another continental plate there. C. two plates are moving past each other there. D. an oceanic plate is converging with a continental plate and subducting there.

B. a continental plate is colliding with another continental plate there.

The rate of plate motion Choose one: A. can range from 100 to 150 cm per year. B. can be expressed as relative plate velocity, which describes movement of one plate in relation to another plate. C. cannot be expressed as absolute plate velocity, which describes movement of a single plate relative to a fixed point, because no points on Earth are actually "fixed". D. can only be determined within a few meters by using the Global Positioning System (GPS).

B. can be expressed as relative plate velocity, which describes movement of one plate in relation to another plate.

Continental mountain ranges such as the Alps and Appalachians are the result of which of the following? Choose one: A. triple junction B. collision C. rifting D. hot spots

B. collision

Low-viscosity lava Choose one: A. is most often a cool-temperature lava. B. has low silica content. C. indicates an area that has high potential for explosive eruptions. D. could logically build a composite volcano.

B. has low silica content.

A mid-ocean ridge Choose one: A. sits lower than the surrounding seafloor because its rock is hotter and less dense than its surroundings. B. is marked by a series of submarine volcanoes. C. is covered by a layer of basalt lava blobs called dikes. D. is a submarine trench that winds through all the world's oceans.

B. is marked by a series of submarine volcanoes.

The center of a mid-ocean ridge is where Choose one: A. molten basalt sinks back into Earth. B. new oceanic lithosphere is being created. C. two continental plates converge. D. you find the oldest, densest, hottest oceanic crust.

B. new oceanic lithosphere is being created.

According to the mantle plume model, hot-spot plumes Choose one: A. produce volcanoes that always coincide with a plate boundary. B. partially melt the base of the overlying lithosphere, and the magma that is formed rises toward the surface. C. stream upward quickly because their hot rock is less dense than the overlying rock. D. are thought to originate at the crust-mantle boundary.

B. partially melt the base of the overlying lithosphere, and the magma that is formed rises toward the surface.

According to current plate tectonics theory, Choose one: A. plates move around by convection on the uppermost part of the mantle. B. plates are composed of the crust and the uppermost part of the mantle. C. plates move at speeds of a few meters per year. D. a continental plate will subduct under an oceanic plate when the two converge.

B. plates are composed of the crust and the uppermost part of the mantle

Oceanic lithosphere Choose one: A. gets warmer as it gets farther from the ridge axis. B. that is 10 million years old is cool enough to be denser than the asthenosphere, so it can sink down through the asthenosphere. C. attains its maximum thickness when it is about 800 million years old. D. gets older and thinner as it gets farther from the ridge axis.

B. that is 10 million years old is cool enough to be denser than the asthenosphere, so it can sink down through the asthenosphere.

Mt. St. Helens erupted explosively in 1980. Geologists find evidence of many eruptions of St. Helens, dating back 37,000 years. The mountain is huge and is composed of layers of lava and pyroclastic debris. Which of the following is, therefore, most likely to be true? Choose one: A. When lava flows from Mt. St. Helens, it will be basalt. B. The volcano is extinct. C. Mt. St. Helens is a stratovolcano (or composite volcano). D. Mt. St. Helens sits on a transform-plate boundary.

C. Mt. St. Helens is a stratovolcano (or composite volcano).

Of the choices below, select the one that accurately pairs the feature with the type of plate boundary at which it occurs. Choose one: A. Accretionary prisms occur at divergent boundaries. B. Black smokers occur at consuming boundaries. C. Trenches occur at subduction zones. D. Median valleys occur at transform boundaries.

C. Trenches occur at subduction zones.

Which of the following volcanic areas is part of the Ring of Fire? Choose one: A. Hawaii B. Iceland C. Krakatau, Indonesia D. Aleutians, Alaska

D. Aleutians, Alaska

The island of Hawaii is the youngest, and the islands get progressively older to the northwest. Plate tectonic theory explains this as Choose one: A. a hot spot moving under the Pacific Plate toward the southeast. B. the rifting of the Pacific Plate, starting at the northwest end of the chain and extending southeast to Hawaii. C. microplates breaking loose from the Pacific Plate as it moves, leaving this chain of islands in its wake. D. a hot spot currently sitting under Hawaii and the Pacific Plate moving across it in a northwesterly direction.

D. a hot spot currently sitting under Hawaii and the Pacific Plate moving across it in a northwesterly direction.

A lahar is A. a collapsed volcanic structure. B. a glowing cloud of pyroclastic fragments and hot gas. C. a lava lake in a summit crater. D. a volcanic mudflow that resembles fluid concrete.

D. a volcanic mudflow that resembles fluid concrete.

Plinian eruptions Choose one: A. occur in Hawaii, where successive eruptions build up layers of basalt. B. are effusive and contain gas bubbles. C. produce a fountain of basaltic lapilli. D. are highly explosive and can destroy the original shape of the volcano.

D. are highly explosive and can destroy the original shape of the volcano.

Rhyolite lava Choose one: A. has less silica than basalt lava has. B. may form a lava fountain above the vent. C. may be squeezed upward and out of the vent to create a lava curtain. D. indicates the tendency for explosive activity.

D. indicates the tendency for explosive activity.

Plate movement is influenced by each of the following EXCEPT Choose one: A. mantle convection, which creates shear at the base of plates. B. ridge push, in which the elevated rocks at the ridge axis push on rocks farther from the ridge. C. slab pull, in which the downgoing oceanic plate exerts a pull on the rest of the plate. D. mantle plumes, which are created when hot rock rises up from the deep mantle and creates melting at the base of the lithosphere.

D. mantle plumes, which are created when hot rock rises up from the deep mantle and creates melting at the base of the lithosphere.

The oceanic lithosphere is

Denser than the continental lithosphere

evidence for plate tectonics includes all of the following except

Fossil correlation between continents

A possible "driving force" for plate motions is

The weight of subduction

____________ first related the symmetrical magnetic patters in seafloor basalts to seafloor spreading at a mid-ocean ridge.

Vine and Matthews

Yellowstone is a classic example of which type of volcanism

a convergent hot spot

a body of solid rock or metal that orbits the sun is called what?

asteroid

Flood basalts form Choose one: A. at continental rifts, where vast bodies of lava flow from fissures. B. from the sudden release of accumulated gas pressure within a volcano. C. when the overriding plate at a subduction zone is composed of oceanic lithosphere. D. when a pyroclastic flow mixes with a nearby water source.

at continental rifts, where vast bodies of lava flow from fissures.

Which of the following is a form of lava? Choose one: A. tuff B. pillow C. ash D. lapilli

b. pillow

hot, thick, and runny lava is called

basilica