Chapter 21-Plate Tectonics and Earth's Interior
13) The theory of seafloor spreading is attributed to
A) Harry Hess.
2) Seismic waves are classified as body waves and surface waves. An example of a body wave is a
A) Primary wave (P-wave).
4) The fastest seismic wave is a
A) Primary wave.
12) Magnetic surveys of the ocean floors reveal
A) alternating stripes of normal and reversed polarity paralleling the mid-Atlantic ridge.
16) What evidence was used to support magnetic pole reversals?
A) apparent polar wandering and alternating magnetic stripe patterns on the ocean floor
12) The upper mantle can be divided into two portions, the
A) asthenosphere (lower zone of the upper mantle) and part of the lithosphere (the top zone of the upper mantle).
30) The upper mantle is the region known as the
A) asthenosphere.
2) At divergent boundaries the dominant rock type is
A) basalt.
29) Transform-fault boundaries usually form
A) between two segments of a mid-ocean ridge.
16) Compressive forces cause the crust to
A) buckle and fold, thereby shortening the crustal surface.
1) In a folded sequence of rocks we find younger rocks at the axis of the fold and older rocks away from the fold axis. The fold is
A) called a syncline.
7) Earth's magnetic field is not stable; throughout geologic time it has changed direction. This change is attributed to
A) changes in the direction of fluid flow in the molten outer core of Earth.
11) The mantle can be separated into two different portions: the lower mantle and the upper mantle. The lower mantle is
A) completely solid due to extreme pressure that prevents iron-rich silica rocks from melting.
39) The crustal surface varies in
A) composition, density, and thickness.
28) The dominant force at convergent boundaries is
A) compression.
20) Which one of the following is not a type of plate collision?
A) continental divergence
5) Water causes partial melting of the mantle at which type of plate boundary?
A) convergent boundaries
37) Isostasy is
A) crustal equilibrium relative to the mantle.
18) Divergent boundaries are areas of
A) crustal formation.
4) Earthquake activity is associated with
A) divergent, convergent, and transform plate boundaries.
5) An anticline is a fold in which the limbs bend
A) downward.
16) The lithosphere rides on top of the asthenosphere. Lithospheric movement causes
A) earthquakes, volcanic activity, and mountain building activity.
3) In the 1950s a plot of the position of the magnetic north pole through time revealed that
A) either the magnetic poles had migrated through time or the continents had moved.
26) Damage from an earthquake is most severe when the
A) epicenter is close to the surface. B) surface material is composed of unconsolidated sediments. C) buildings and structures are poorly constructed. D) all of the above
11) Earth's internal layers were discovered by studying the movement of P- and S- waves through Earth's interior. In comparison to S-waves, the movement of P-waves is
A) fast, compressing and expanding the rock as they move through it.
1) Granite does not readily form near oceanic-oceanic convergent boundaries because
A) granite forms from granitic magma and most oceanic material is basaltic in origin. B) the magma formed at this type of boundary is not conducive to producing granitic type rocks. C) oceanic-oceanic convergence often results in the eruption of andesitic lavas. D) all of the above
14) Continental crust extends farther down into the mantle than oceanic crust because
A) it is thicker than oceanic crust.
23) The majority of earthquakes occur where
A) lithospheric plates meet.
21) The Earth's layer with plastic-like behavior is the
A) mantle.
16) The longest mountain chain in the world is the
A) mid-ocean ridge.
15) A fault in which the footwall has moved down relative to the hanging wall is called a
A) normal fault.
9) Mountains tend to form in long narrow ranges because
A) of plate convergence—plates coming together.
1) Plate tectonics differs from continental drift because it
A) provides a credible driving force.
9) When rock is subjected to compressive force, it may fault. If rocks in the hanging wall are pushed up over rocks in the footwall, it is called a
A) reverse fault.
22) Tsunami are correctly referred to as
A) seismic sea waves.
10) Earth's internal layers were discovered by studying
A) seismic waves.
26) Subduction occurs as a result of
A) slab pull—gravity pulls older and denser lithosphere downward.
32) The San Andreas fault
A) stretches from the Gulf of California to Cape Mendocino, California, and separates the Pacific Plate from the North American Plate.
25) The process in which one plate bends and descends beneath another plate is called
A) subduction.
17) Divergent boundaries are areas of
A) tensional forces that stretch the crust and generate a spreading center.
12) The theory of plate tectonics states that
A) the lithosphere is broken up into several plates that move about as a result of convective motion in the asthenosphere.
4) According to the theory of seafloor spreading, molten rock is rising up along
A) the mid-ocean ridges.
1) The speed of a seismic wave depends on
A) the type of material it travels through.
9) Oceans are about four times as deep as mountains are high. At the bottom of the ocean are
A) towering mountains, deep valleys, and deep trenches near the continental borders.
25) Compressive stress causes rocks to buckle and fold. In a syncline fold, the rocks at the fold axis (the core) are
A) younger than those away from the axis.
4) The theory of continental drift is attributed to
B) Alfred Wegener.
15) How did seafloor spreading suggest a driving force for continental drift?
B) Seafloor spreading pushes continents.
5) Evidence to support the fact that Earth's central core is solid can be attributed to
B) an increase in P-wave velocity as they encounter and move through the inner core.
15) In comparison to S-waves, P-waves
B) are the fastest of all seismic waves and the first to register on a seismograph.
11) If the path of polar wandering found from two continents are not the same, then we can say that
B) at least one of the continents has moved.
21) The energy in an earthquake is released
B) before the quake, after the quake, and during the quake.
2) In a folded sequence of rocks we find older rocks at the axis of the fold and younger rocks away from the fold axis. The fold is
B) called an anticline.
14) In comparison to S-waves, P-waves
B) can travel through solid granite, magma, water and/or air.
34) Movement of the lithosphere
B) causes earthquakes and volcanic activity.
38) Compared with oceanic crust, continental crust is very buoyant because it is
B) composed of granitic rocks whereas oceanic crust is composed of basaltic rocks.
19) Reverse faults are the result of
B) compression.
2) In a reconstruction of Earth's geologic past, the continents of Africa and South America fit best along the
B) continental shelves.
11) Two boundaries associated with seafloor spreading centers are
B) divergent boundaries and transform fault boundaries.
23) Another term for a spreading center is
B) divergent boundary.
12) The Richter magnitude scale measures an earthquake's
B) energy in terms of ground shaking.
6) The Earth's magnetic field is attributed to the
B) flow of molten fluid in Earth's outer core.
20) The outer core
B) flows fast enough to power Earth's magnetic field.
4) Convection in Earth's mantle is attributed to
B) gravity and heat flow.
31) Thermal convection movement in the upper mantle
B) greatly influences Earth's surface features.
27) A tsunami is unlike most other water waves mainly because it
B) has a very long wavelength.
8) The Earth's magnetic field
B) has reversed itself many times.
29) The mantle is composed of
B) iron-rich silicate rocks.
10) The rate of seafloor spreading can be calculated by
B) knowing the dates for magnetic pole reversals, and the distance from the location of a known reversal site to the ocean ridge.
10) Continental crust is
B) less dense than oceanic crust.
32) The crustal surface and the uppermost part of the mantle is called the
B) lithosphere.
6) Tectonic plates are composed of the
B) lithosphere.
6) A seismograph
B) measures ground movement.
4) Because S-waves do not travel through Earth's outer core, scientists inferred that the outer core is
B) molten liquid.
3) As hot mantle rock rises, it expands. As it expands it cools. This cooler rock is
B) more dense so it sinks. This contributes to the heat flow convection process.
14) The main idea of seafloor spreading is that
B) new crust forms at a spreading center and old crust is recycled at a subduction zone.
7) Secondary waves can travel through all areas of Earth except the
B) outer core.
8) What evidence did Wegener use to support his hypothesis of continental drift?
B) paleoclimatic data
7) The theory of seafloor spreading is supported by
B) paleomagnetic analysis of the ocean's floor.
13) We can say that Earth's crust floats on the mantle because
B) part of the mantle is hot enough to flow as a plastic solid.
5) The concept of seafloor spreading states that
B) seafloor is created at mid-ocean ridges and destroyed at deep ocean trenches.
18) The Mohorovicic discontinuity was discovered by observing
B) seismograms of an earthquake.
11) The San Andreas fault in California is a
B) strike slip fault.
28) Earthquakes are caused by the
B) sudden release of energy that is stored elastically in deforming rocks.
27) The dominant force at divergent boundaries is
B) tension.
6) When you stretch a rubber band, you are applying
B) tensional stress.
7) The stress that occurs when material is pulled apart is called
B) tensional stress.
32) Where does a tsunami usually occur?
B) underwater reverse fault
13) Regions in which earthquakes are common are also regions in which
B) volcanoes are common.
5) Wegener's theory of continental drift
B) was not accepted by the scientific community of the early 1900s.
4) The Richter magnitude scale is logarithmic, each 1-point increase on the scale corresponds to a
C) 10-fold increase in the amplitude of ground shaking.
8) If seafloor spreading creates new lithosphere, does the size of Earth change?
C) No, older crust is recycled back into the asthenosphere.
17) Why was it so important to survey the ocean floors?
C) To know the topography and possible hiding places for submarines.
22) Earth's core is probably composed of
C) an iron-nickel alloy.
33) The lithosphere floats atop the
C) asthenosphere.
3) In an undeformed sequence of rocks, the youngest rocks are found
C) at the top of the rock sequence.
6) The ocean crust
C) becomes progressively older away from the mid-ocean ridge.
13) In comparison to P-waves, S-waves
C) can travel only through solids—not in fluids.
19) The Mohorovicic discontinuity occurs because of a
C) change in the composition of rocks on both sides of the boundary.
31) Volcanoes do not form at which type of convergent plate boundary?
C) continental—continental convergent boundaries
3) Volcanic activity is associated with
C) divergent and convergent boundaries.
30) Convection in the mantle is caused primarily by
C) gravity and temperature differences.
10) The relative movement of a strike-slip fault is
C) horizontal.
8) The outer core is
C) liquid.
3) Motion in a P-wave is
C) longitudinal.
3) The Mohorovicic discontinuity marks the change in rock density elasticity between the
C) mantle and the crustal surface.
9) The asthenosphere is part of the
C) mantle.
19) Spreading centers occur along
C) mid-ocean ridges.
5) When the magnetic field of Earth is reversed,
C) newly formed mineral grains on the ocean floor are magnetized according to the new orientation of the magnetic field.
10) Most of the state of Nevada is in the Basin and Range Province. The predominant active fault for this region is
C) normal faulting.
8) Compression cannot produce
C) normal faults.
18) Rocks in the core of an anticline are ________ than rocks away from the core.
C) older
8) The movement of seismic waves through Earth's interior provides evidence of internal layering. The first boundary discovered was between the
C) outer core and the mantle.
3) Which of the following did Alfred Wegener not use to support his theory of continental drift?
C) paleomagnetic data
14) Most of Earth's seismic activity, volcanism, and mountain building occur along
C) plate boundaries.
6) Tectonic interaction between plate boundaries does not explain
C) polar wandering.
24) The inner core is solid because
C) pressure from the weight of the surrounding layers prevents the inner core from melting.
27) The primary evidence that the outer core is molten is an abrupt
C) stop of S-wave propagation, and a decrease in P-wave velocity.
23) Evidence to support that the inner core is solid and the outer core is liquid comes from
C) the wave shadow effect of P- and S-waves, and the increase in velocity of P-waves as they encounter the solid inner core.
25) The outer core is liquid because
C) there is less weight, and thus less pressure on it.
14) The moment magnitude scale measures the energy released by an earthquake. For each increase in magnitude, the energy released increases
D) 30 times.
1) Which seismic waves produce a wave shadow?
D) P- and S- waves
24) Transform faults are areas of crustal
D) accommodation and plate movement.
5) Earthquake P-waves
D) are longitudinal vibrations similar to sound waves.
7) The theory of continental drift is supported by paleoclimatic data, the jig-saw fit of the continents
D) at their continental margins, and paleontology.
35) The top of the mantle is the same as the
D) base of the crust.
17) Tensional forces cause the crust to
D) break and fracture, thereby lengthening the crustal surface.
20) When stress exceeds a rock's elastic limit, the rock
D) can lose its original form and either break or flow.
36) The Earth's lithosphere
D) consists of the crust and the uppermost part of the mantle.
15) The lithosphere includes
D) continental and oceanic crust and the upper part of the mantle.
29) Magma is generated at all of these plate boundaries except
D) continental-continental convergent boundaries.
30) The Himalayan Mountains formed at which type of plate boundary?
D) continental—continental convergent boundary
2) Lithospheric plates move in response to
D) convection cells generated by gravity and heat flow in the mantle.
24) Rocks begin to deform when they are stressed. Near Earth's surface, when stress is severe, the rock
D) has plastic deformation—it faults and fractures.
1) Detailed mapping of the ocean floors revealed
D) huge mountain ranges on the ocean floor, and deep trenches near some of the continents.
13) The Mercalli scale measures an earthquake's
D) intensity, damage, and overall effect.
2) Paleomagnetism from a rock gives information on the
D) magnetic field at the time the rock was formed.
6) Alfred Wegener supported his theory of continental drift by
D) making a connection between rocks, rock structures, and plant and animal fossils found in both Africa and South America.
15) The oldest rocks are found
D) on continental land.
22) Convergent boundaries are regions of
D) plate collision, subduction, and mountain building.
21) Convergent boundaries are areas of
D) plate collision.
12) Earth's internal layers were discovered by studying the propagation of P- and S- waves through Earth's interior. In comparison to P-waves, the movement of S-waves are
D) slower and they can only travel through solids, not liquids.
2) P-waves travel faster through the inner core than the outer core because the inner core is
D) solid.
7) Plate tectonics states that
D) tectonic plates are in slow, but constant motion.
1) The theory of continental drift is supported by paleoclimate data, paleontology, and
D) the jig-saw fit of the continents at their continental margins.
28) The Earth's magnetic field is generated in
D) the outer core.
31) The occurrence of earthquakes in the absence of seafloor spreading, oceanic trenches, or
D) transform fault boundaries between plates.
33) According to plate tectonic theory, the San Andreas fault is a
D) transform fault.
17) The thickness of Earth's crust
D) varies from 10 km under the oceans to 60 km under the continents.
26) The outer core is thought to be molten because it
D) will not transmit S-waves.
9) An Earthquake occurs as
E) energy released from Earth's interior travels in the form of seismic waves to Earth's surface.
