Chapter 3 (GEOL107)

Plate tectonics theory was widely accepted by scientists in what decade? Choose one: A. 1980s B. 1930s C. 1920s D. 1960s

A. 1980s

The name given by Alfred Wegener to the super continent he believed existed prior to the current continents was: A. Pangaea B. Atlantis C. Euroamerica D. Pantheon

A. Pangaea

Identify the true statement. Choose one: A. To keep the Earth's surface area constant, the amount of seafloor spreading must equal the amount of subduction. B. Ocean floor is created by the process of subduction. C. Subduction causes continents to move apart; seafloor spreading brings them together. D. Ocean basins get narrower as a result of seafloor spreading.

A. To keep the Earth's surface area constant, the amount of seafloor spreading must equal the amount of subduction.

Wegener's proposal that the continents had once fit together as a single supercontinent was rejected by geologists at the time because... A. Wegener could not provide a driving force strong enough. B. the continents did not fit together tightly enough. C. the fossil evidence was inconclusive. D. the distribution of climatic belts did not make sense in that configuration.

A. Wegener could not provide a driving force strong enough.

Limestone reefs and salt deposits are important in the reconstruction of the Earth's history because they... A. can be used to infer the ancient climate of the Earth; they are deposited in environments that are restricted to warm climates. B. automatically provide age information; all such deposits occurred between 200 and 400 million years ago. D. are deposited in warm climates today, but there is good reason to think that they were deposited in cold climates millions of years ago. E. pinpoint the locations of old subduction zones.

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

The rate of seafloor spreading Choose one: A. dictates the rate at which ocean basins grow wider. B. affects the magnetic polarity of the ocean floor. C. depends on the type of plate boundary (i.e., convergent, transform) at which it occurs. D. is on the order of meters per year.

A. dictates the rate at which ocean basins grow wider.

Marine magnetic anomalies result from seafloor spreading in conjunction with Choose one: A. magnetic polarity reversals. B. global warming. C. magnetic storms on the surface of the Sun. D. apparent wander of the magnetic poles.

A. magnetic polarity reversals.

Magnetic reversals Choose one: A. reflect changes in the direction of the flow of molten iron in the Earth's outer core. B. happen slowly as the magnetic poles wander and finally cross the equator. C. are localized phenomena that are recorded differently in the rock record at various locations. D. are caused by lightning strikes and/or chemical reactions.

A. reflect changes in the direction of the flow of molten iron in the Earth's outer core.

Pangaea Choose one: A. started to break apart during the Mesozoic. B. is the name for the first supercontinent; others have existed more recently. C. broke apart because of the force created by the Earth's rotation. D. means all for one.

A. started to break apart during the Mesozoic.

Which of the following lines of evidence for continental drift/plate tectonics was found after Wegener published his theory? Choose one: A. the existence of mid-ocean ridges, where seafloor spreading starts B. evidence of similar paleoclimates in belts across Pangaean latitudes. C. the matching of the distribution of similar fossils across oceans D. the matching fit of the outline of some of the continents

A. the existence of mid-ocean ridges, where seafloor spreading starts

The Earth's magnetic field is created by Choose one: A. the flow of liquid iron in the Earth's molten outer core. B. centrifugal force pushing on the Earth's crust. C. convecting iron-rich silicates in the Earth's mantle. D. the rotation of the planet on its axis.

A. the flow of liquid iron in the Earth's molten outer core.

__________ first related the symmetrical magnetic patterns in seafloor basalts to seafloor spreading at a mid-ocean ridge. A. Wegener and Wilson B. Vine and Matthews C. Evans and Novak D. Matthews and Marks

B. Vine and Matthews

Alfred Wegener proposed the idea of continental drift after he observed evidence from fossils, glacial deposits, and the fit of the continents that suggested all of the continents were once Choose one: A. aligned north to south along the prime meridian during the late Cenozoic. B. combined to form a supercontinent (which he termed Pangaea) in the late Paleozoic through the Mesozoic. C. aligned east to west along the equator during the late Mesozoic through the Cenozoic. D. combined to form a supercontinent (which he termed Rodinia) in the Proterozoic.

B. combined to form a supercontinent (which he termed Pangaea) in the late Paleozoic through the Mesozoic.

Bathymetric maps of the seafloor show Choose one: A. bands of vertical fractures (fracture zones) that run parallel to mid-ocean ridges. B. elongate trenches that reach 8 to 10 km deep (enough to hold Mt. Everest). C. a flat, featureless deep seafloor. D. broad, flat abyssal plains that sit at depths of 1 to 2 km below sea level.

B. elongate trenches that reach 8 to 10 km deep (enough to hold Mt. Everest).

The age of oceanic crust Choose one: A. is greatest at the mid-ocean ridge and least farthest from the ridge. B. has been determined by radiometric dating. C. is the same throughout the world's oceans. D. indicates that the oldest oceanic crust is approximately 600 million years old.

B. has been determined by radiometric dating.

Oceanic crust Choose one: A. is the same age as continental crust. B. is covered by a thin blanket of sediment that thickens away from the ridge axis. C. has not been sampled directly, because it is too deep beneath the ocean. D. has the same composition as continental crust.

B. is covered by a thin blanket of sediment that thickens away from the ridge axis.

The apparent tendency of the north (or south) magnetic pole to vary in position over time is termed Choose one: A. magnetic declination. B. polar wander. C. dipole. D. magnetic inclination.

B. polar wander.

The magnetic dip preserved in a rock indicates A. how far east or west of north the rock formed B. the rock's magnetic latitude at the time that it formed C. how deep in the crust the magma crystallized D. how far from a spreading ridge the rock has traveled

B. the rock's magnetic latitude at the time that it formed

The magnetic dip preserved in a rock indicates... A. how far east or west of north the rock formed B. the rock's magnetic latitude at the time that it formed C. how deep in the crust the magma crystallized D. how far from a spreading ridge the rock has traveled

B. the rock's magnetic latitude at the time that it formed

Radiometric dating of a magnetic anomaly stripe of rock that is 225 km away from the mid-ocean ridge axis gives an age of 4.5 million years. Assuming a constant rate, seafloor spreading in this area occurs at a rate of Choose one: A. 1,012.5 km per year. B. 50 km per year. C. 5 cm per year. D. 20,000 cm per year.

C. 5 cm per year.

Identify the statement that is true about the ocean floor. Choose one: A. Oceanic crust has a lower density than continental crust has. B. It is covered by a layer of sediment composed of sand and pebbles. C. The heat flow through it is greatest at mid-ocean ridges. D. Oceanic crust contains granite and metamorphic rocks.

C. The heat flow through it is greatest at mid-ocean ridges.

A "polar-wander" curve shows A. how magnetic poles have moved on the earth. B. how the sea floor has spread. C. how continents have moved, or drifted, relative to the magnetic poles. D. how polar glacier ice has moved across continents.

C. how continents have moved, or drifted, relative to the magnetic poles.

A "polar-wander" curve shows... A. how magnetic poles have moved on the earth. B. how the sea floor has spread. C. how continents have moved, or drifted, relative to the magnetic poles. D. how polar glacier ice has moved across continents.

C. how continents have moved, or drifted, relative to the magnetic poles.

A negative magnetic anomaly Choose one: A. is created when weak magnetic forces in basalt grains add to the force produced by the Earth's dipole. B. describes the sawtooth pattern of magnetic signal strength measured along the Atlantic Ocean seafloor. C. is indicated when a magnetometer measures intervals of magnetism that are weaker than expected. D. occurs when the Earth's magnetic field measured in ancient rocks is the same as it is today.

C. is indicated when a magnetometer measures intervals of magnetism that are weaker than expected.

The reversals of the Earth's magnetic field were first discovered by Choose one: A. studying the composition of silicate rocks. B. observing the geothermal gradient in gold mines 3.5 km below the surface. C. studying the paleomagnetism of volcanic rocks. D. observing an abrupt change in seismic wave velocities.

C. studying the paleomagnetism of volcanic rocks.

Which of the following lines of evidence was discovered after Wegener developed his theory that continents drift? Choose one: A. the distribution of fossil species B. the location of ancient till deposits and striations that indicated glacial movement toward the interior of continents C. the presence of earthquakes in seismic belts along trenches, ridges, and fracture zones D. the presence of matching mountain chains on continents currently separated by oceans

C. the presence of earthquakes in seismic belts along trenches, ridges, and fracture zones

Identify the true statement. Choose one: A. All polarity chrons are the same length of time; they differ only in the magnetic strengths they represent. B. The width of each rock stripe is a measure of how long the polar direction took to change. C. The series of rock stripes perpendicular to and bilaterally symmetric across the mid-ocean ridge records the sequence of the Earth's magnetic reversals over time. D. Positive magnetic anomalies occur over areas of seafloor when the poles of the Earth's magnetic field and the paleopoles preserved in the seafloor basalt agree.

D. Positive magnetic anomalies occur over areas of seafloor when the poles of the Earth's magnetic field and the paleopoles preserved in the seafloor basalt agree.

Which of the following issues initially prevented widespread acceptance of Alfred Wegener's continental drift hypothesis? Choose one: A. the presence of ancient glacial deposits in equatorial regions B. the presence of identical terrestrial species on opposite sides of the Atlantic Ocean C. the apparent match of the coastlines of Africa and South America D. Wegener's lack of a good mechanism to explain why the continents moved

D. Wegener's lack of a good mechanism to explain why the continents moved

Glaciers Choose one: A. leave deposits of sediment called bathymetries. B. occurred during the late Paleozoic in the same places they exist today. C. have occurred only at high altitudes or in polar regions. D. are slow-moving sheets of ice on land.

D. are slow-moving sheets of ice on land.

Plate tectonics theory took decades to be accepted Choose one: A. because most of Wegener's ideas turned out to be wrong. B. because of pure stubbornness by the scientific community. C. because climate, fossil distributions, and land shape offered conflicting evidence. D. because Wegener couldn't explain how continents moved.

D. because Wegener couldn't explain how continents moved.

Wegener's evidence for a united Pangaea comes from the fossil record of which type of organisms? A. plant pollen B. plankton C. marine animals D. land animals

D. land animals

Wegener's evidence for a united Pangaea comes from the fossil record of which type of organisms? A. plant pollen B. plankton C. marine animals D. land animals

D. land animals

Cynognathus, Glossopteris, Mesosaurus, and Lystrosaurus are Choose one: A. the names of the most recent periods of magnetic reversal. B. distinctive assemblages of rocks. C. names of supercontinents that existed before Pangaea. D. land-dwelling species whose distribution suggested joined continents.

D. land-dwelling species whose distribution suggested joined continents.

The paleomagnetic record is Choose one: A. a puzzle; it contradicts the seafloor-spreading concept. B. asymmetric across the mid-ocean ridge. C. preserved only in basalt layers on the seafloor. D. preserved in stripes of rock parallel to the mid-ocean ridge.

D. preserved in stripes of rock parallel to the mid-ocean ridge.

Wegener's proposal that the continents had once fit together as a single supercontinent was rejected by geologists at the time because A. Wegener could not provide a driving force strong enough. B. the continents did not fit together tightly enough. C. the fossil evidence was inconclusive. D. the distribution of climatic belts did not make sense in that configuration.

D. the distribution of climatic belts did not make sense in that configuration.

When magma cools, magnetic minerals become (blank).

Magnetized