Question 1

Figure 12.11 
-Refer to Figure 12.11 in your textbook. Which option correctly matches isotopic age and polarity of the seafloor.
A) 2.29 million years: reverse polarity; 1.37 million years: reverse polarity
B) 3.42 million years: reverse polarity; 1.74 million years: reverse polarity
C) 1.26 million years: normal polarity; 1.92 million years: reverse polarity
D) 2.12 million years: normal polarity; 3.01 million years: normal polarity

Accepted Answer

The correct answer is A because the figure shows that 2.29 million years ago, the seafloor had reverse polarity, and 1.37 million years ago, the seafloor also had reverse polarity.

Question 2

Which statement is true about the lithosphere?
A) The lithosphere is thickest at the mid-ocean ridges because of the quantity of magma that flows up to the surface.
B) The lithosphere gets thicker as distance from the ridge increases, because it cools and the boundary between the lithosphere and asthenosphere occurs at greater depth.
C) The lithosphere maintains its thickness as distance from the ridge increases, because the boundary between the lithosphere and asthenosphere remains at a constant temperature and depth.
D) The lithosphere gets thinner as distance from the ridge increases, because decompression melting occurs with decreased pressure.

Accepted Answer

The lithosphere gets thicker as distance from the mid-ocean ridge increases, because it cools and the boundary between the lithosphere and asthenosphere occurs at greater depth. As magma rises to the surface at the ridge, it cools and solidifies, forming new lithosphere. As the lithosphere moves away from the ridge, it cools further, becoming thicker and increasing in depth. This is due to the fact that the mantle beneath the lithosphere gets cooler with depth, and the boundary between the lithosphere and asthenosphere occurs at a constant temperature, so it occurs at greater depth as the lithosphere thickens.

Question 3

Using Figure 12.11 in your textbook, which option correctly identifies a time that polarity changed from normal to reverse and back?
A) normal to reverse: 3.04 million years ago, reverse to normal: 2.60 million years ago
B) normal to reverse: 2.60 million years ago, reverse to normal: 1.79 million years ago
C) normal to reverse: 3.33 million years ago, reverse to normal: 3.04 million years ago
D) normal to reverse: 1.79 million years ago, reverse to normal: 0.99 million years ago

Accepted Answer

Option C is correct because it identifies a time period where the polarity changed from normal to reverse at 3.33 million years ago and then back to normal at 3.04 million years ago, which aligns with known geomagnetic reversal events.

Question 4

Which of the following is true of divergent and convergent plate movement?
A) The direction of plate movement is the same.
B) Convergent plate movement is less symmetrical than divergent plate movement.
C) Material is destroyed with both plate movements.
D) Both plates have boundaries.

Accepted Answer

The answer of Which of the following is true of...

Question 5

The following statements relate to processes that occur because of plate subduction. Which of the following statements is not true?
A) Earthquake foci are deeper further from a deep-sea trench.
B) Mountains form further from a convergent boundary than from a divergent boundary.
C) Volcanoes of this kind tend to have a single type of magma.
D) Deep-sea trenches mark the plate boundary.

Accepted Answer

Volcanoes associated with plate subduction zones typically exhibit a range of magma types, not just a single type. This diversity in magma composition is due to the complex processes of melting, assimilation, and differentiation that occur as the subducting plate descends and interacts with the overlying mantle and crust.

Question 6

How fast is North America moving away from Africa?
A) 3 cm/year
B) 3 m/year
C) 3 mm/year
D) 3 km/year

Accepted Answer

North America is moving away from Africa at a rate of approximately 3 cm/year due to the tectonic plate movements governed by the process of continental drift.

Question 7

Why are so few volcanoes mapped in the middle of the oceans?
A) The middle of the oceans corresponds with the middle of tectonic plates, so there are only hot-spot volcanoes there.
B) Geologists cannot pinpoint the locations of many recently active seafloor volcanoes.
C) There are only convergent plate boundaries under the ocean, which are less likely to have volcanoes than transform or divergent boundaries.
D) There are only divergent plate boundaries under the ocean, which are less likely to have volcanoes than transform or convergent boundaries.

Accepted Answer

Geologists cannot pinpoint the locations of many recently active seafloor volcanoes.

Question 8

What do mountain belts such as the Caledonian and Appalachian Mountains suggest to scientists?
A) By uniformitarian principles, the tectonic plates may have been in different positions in the past.
B) The theory of tectonic plate action is not sufficient to explain all mountain building.
C) The continental lithosphere is more rigid than the oceanic lithosphere.
D) By evaluation of the deformations, the asthenosphere is more rigid than the lithosphere.

Accepted Answer

The presence of mountain belts such as the Caledonian and Appalachian Mountains suggest to scientists that the tectonic plates may have been in different positions in the past, which supports the principle of uniformitarianism.

Question 9

Which of the following determines why subducting plates sink at a particular location?
A) the heat of the asthenosphere at the location
B) the density of the asthenosphere at the location
C) the pushing movement of the adjacent plate
D) the density of the lithosphere at the location

Accepted Answer

The density of the lithosphere at the location determines whether or not subducting plates will sink. If the subducting plate is denser than the surrounding lithosphere, it will sink. If it is not as dense, it will not sink and will instead be pushed back up.

Question 10

After movement, the interior parts of ice slabs and continental plates
A) may be stretched.
B) may be rippled up to form hills, ridges, and mountains.
C) may be cracked to form crevices.
D) remain unchanged.

Accepted Answer

The answer of After movement, the interior parts of ice...

Question 11

Figure 12.25 
-Using Figure 12.25 in your textbook, which of the following is not a normal consequence of an oceanic-oceanic convergent plate boundary?
A) The denser crust subducts the less dense plate.
B) Thrust faults lift up above the subduction zone.
C) A volcanic island arc forms above where the subducting plate melts.
D) A trench forms at the location where subduction begins.

Accepted Answer

Thrust faults do not normally lift up above the subduction zone at an oceanic-oceanic convergent plate boundary. Instead, they typically cause strong earthquakes due to the subducting plate being forced downward.

Question 12

At what point does the Wadati-Benioff zone have to end?
A) when it runs into the deep-sea trench
B) when it runs up against another plate
C) when it reaches a zone that is too hot
D) when it reaches Earth's surface

Accepted Answer

The Wadati-Benioff zone ends when it reaches a zone that is too hot, which causes the subducting slab to melt and decompose. This typically occurs at depths where the temperature is high enough to induce these changes, rather than at the Earth's surface, a deep-sea trench, or against another plate.

Question 13

Why does the heat flow dip east of the location where the Juan de Fuca Plate subducts beneath the North American Plate?
A) The ocean water cools the rock in the trench.
B) The cold subducted lithosphere dips there.
C) The rock is denser and cooler there.
D) The rock remained cold there after the most recent ice age.

Accepted Answer

The cold subducted lithosphere dips there. As the Juan de Fuca Plate subducts beneath the North American Plate, it pulls cold lithosphere down with it, causing a dip in the heat flow.

Question 14

How do scientists measure the age of rocks at mid-ocean ridges?
A) radioactive dating methods
B) comparison of rock samples on mountain ranges
C) fossil stratification and the principle of horizontality
D) magnetic polarity measurements

Accepted Answer

Scientists measure the age of rocks at mid-ocean ridges using magnetic polarity measurements. As new oceanic crust is formed at the ridges, it records the direction of Earth's magnetic field at the time of its formation. By analyzing the magnetic polarity of rock samples taken from different ages along the ridge, scientists can create a timeline of magnetic reversals and determine the age of the rocks.

Question 15

Which feature is not usually caused by convergent boundaries?
A) volcanoes
B) deep-sea trenches
C) rift valleys
D) mountains

Accepted Answer

Rift valleys are usually caused by divergent boundaries, where tectonic plates move away from each other, creating a rift or a gap. Convergent boundaries are where two tectonic plates move towards each other, causing compression and the formation of features such as mountains, volcanoes, and deep-sea trenches.

Question 16

What evidence suggests to scientists that magma generation at convergent boundaries is different than magma generation at mid-ocean ridges?
A) crystal size
B) igneous action
C) partial melting caused by water
D) lava composition

Accepted Answer

The answer of What evidence suggests to scientists that magma...

Question 17

Approximately what percent of lithosphere deformation occurs at plate boundaries?
A) 60%
B) 70%
C) 80%
D) 90%

Accepted Answer

The answer of Approximately what percent of lithosphere deformation occurs...

Question 18

What is true of Iceland?
A) Iceland is contracting at a rate of about 4 mm per year due to melting at the Mid-Atlantic Ridge.
B) Iceland is stretching at a rate of about 4 mm per year due to expansion at the Mid-Atlantic Ridge.
C) Iceland is contracting at a rate of about 4 m per year due to melting at the Mid-Atlantic Ridge.
D) Iceland is stretching at a rate of about 4 m per year due to expansion at the Mid-Atlantic Ridge.

Accepted Answer

Iceland is located on the Mid-Atlantic Ridge, which is a divergent boundary where two tectonic plates are moving apart. This causes the island to stretch and expand at a rate of about 4 mm per year. There is no evidence to suggest that Iceland is melting or contracting at a rate of 4 m per year, which is a much larger scale of change than what is observed.

Question 19

What is a typical depth of a deep-sea trench?
A) 5 m
B) 5 km
C) 50 m
D) 50 km

Accepted Answer

Deep-sea trenches typically have depths around 5 kilometers (km), representing some of the deepest parts of the ocean.

Question 20

Why did scientists reject Wegener's idea about how continents moved from Pangea to their present locations?
A) Scientists did not believe in a fluid mantle.
B) Scientists did not believe in uplift of continents from the ocean floor.
C) Scientists did not believe that the continental lithosphere could be stronger than the oceanic lithosphere.
D) Scientists were not convinced by his puzzle-like matching of continents into Pangea.

Accepted Answer

The answer of Why did scientists reject Wegener's idea about...

Quiz 12: Global Tectonics: Plates and Plumes

Figure 12.11 -Refer to Figure 12.11 in your textbook. Which option correctly matches isotopic age and polarity of the seafloor.

Which statement is true about the lithosphere?

Using Figure 12.11 in your textbook, which option correctly identifies a time that polarity changed from normal to reverse and back?

Which of the following is true of divergent and convergent plate movement?

The following statements relate to processes that occur because of plate subduction. Which of the following statements is not true?

How fast is North America moving away from Africa?

Why are so few volcanoes mapped in the middle of the oceans?

What do mountain belts such as the Caledonian and Appalachian Mountains suggest to scientists?

Which of the following determines why subducting plates sink at a particular location?

After movement, the interior parts of ice slabs and continental plates

Figure 12.25 -Using Figure 12.25 in your textbook, which of the following is not a normal consequence of an oceanic-oceanic convergent plate boundary?

At what point does the Wadati-Benioff zone have to end?

Why does the heat flow dip east of the location where the Juan de Fuca Plate subducts beneath the North American Plate?

How do scientists measure the age of rocks at mid-ocean ridges?

Which feature is not usually caused by convergent boundaries?

What evidence suggests to scientists that magma generation at convergent boundaries is different than magma generation at mid-ocean ridges?

Approximately what percent of lithosphere deformation occurs at plate boundaries?

What is true of Iceland?

What is a typical depth of a deep-sea trench?

Why did scientists reject Wegener's idea about how continents moved from Pangea to their present locations?