Question 1

All of the following processes aid the lithosphere in becoming denser than the asthenosphere except

Accepted Answer

Decompression melting is a process that produces magma from asthenosphere material, which then solidifies to form new lithosphere. This does not contribute to the lithosphere becoming denser than the asthenosphere. The other three processes listed (cooling and contracting, thickening by addition to the base, and metamorphosing into eclogite) involve changes to existing lithosphere that can result in an increase in density relative to the asthenosphere.

Question 2

Figure 12.43 
-According to Figure 12.43 when did the Appalachian Mountains form?

Accepted Answer

According to the geologic timeline on Figure 12.43, the Appalachian Mountains formed during the Alleghenian orogeny which occurred approximately 300 million years ago.

Question 3

Judge the following sentence according to the criteria given below. Seafloor elevations decrease away from mid-ocean ridges because cooling lithosphere contracts, becomes denser and sinks down into the weak asthenosphere.

Accepted Answer

The assertion is correct, as seafloor elevations do indeed decrease away from mid-ocean ridges. The reason given is also correct, as cooling lithosphere does contract, become denser, and sink into the asthenosphere. This explanation is valid and consistent with established geologic processes.

Question 4

Which of the following is an example of a slow moving plate?

Accepted Answer

The North American Plate is an example of a slow moving plate. It is moving at a rate of approximately 2.3 centimeters per year.

Question 5

The seafloor spreading hypothesis predicts that the mid-ocean ridges should be locations of rising asthenosphere. This prediction is supported by seismic data that indicates

Accepted Answer

Slower seismic wave velocities at the ridges indicate that the material there is hotter and possibly in a partially molten state, which is consistent with the idea of rising asthenosphere material at mid-ocean ridges as proposed by the seafloor spreading hypothesis.

Question 6

According to the Continental Drift hypothesis the continents and ocean basins on the same plate move together.

Accepted Answer

The Continental Drift hypothesis suggests that continents move across the Earth's surface over geological time, but it does not imply that continents and ocean basins on the same plate move together. Instead, it was later understood through plate tectonics that continents and ocean basins are part of tectonic plates that move independently.

Question 7

All volcanic eruptions over the past 10,000 years occurred along or near plate boundaries.

Accepted Answer

While many volcanic eruptions occur along or near plate boundaries due to the movement of tectonic plates, there are also volcanic eruptions that occur away from plate boundaries, such as those caused by mantle plumes or hotspots (e.g., the Hawaiian Islands).

Question 8

Judge the following sentence according to the criteria given below. Plate tectonic works because lithosphere is less dense than asthenosphere at divergent boundaries and more dense than asthenosphere at convergent boundaries.

Accepted Answer

The assertion that plate tectonic works because of the density differences is correct and the reason that lithosphere is less/more dense than asthenosphere at divergent/convergent boundaries is also correct and valid.

Question 9

Figure 12.43 
-According to Figure 12.43 when did the Caledonian Mountains form?

Accepted Answer

Figure 12.43 shows that the Caledonian Mountains formed during the Ordovician Period, which occurred approximately 430 million years ago.

Question 10

Most active mountain belts are located near plate boundaries.

Accepted Answer

Active mountain belts are typically located near plate boundaries where tectonic activity, such as subduction or collision, creates the conditions for mountain building. Examples include the Andes in South America, the Himalayas in Asia, and the Rocky Mountains in North America.

Question 11

Judge the following sentence according to the criteria given below. Continental crust dominated by rocks older than 1 billion years but no ocean crust older than 180 million years exists because oceanic crust is created at mid-ocean ridges.

Accepted Answer

The answer of Judge the following sentence according to the...

Question 12

The Wadati-Benioff zone outlines the ________ at a convergent boundary.

Accepted Answer

The Wadati-Benioff zone is a band of earthquakes that delineates the location of a subducting plate at a convergent boundary.

Question 13

300 million years ago Ancestral North America was

Accepted Answer

300 million years ago, North America was part of the supercontinent Pangea, which included all of the world's continents joined together.

Question 14

A present day example of an oceanic-oceanic convergent plate boundary is

Accepted Answer

Indonesia is located on the boundary between the Australian Plate and the Eurasian Plate, which are both oceanic plates. This convergence has resulted in the formation of the Sunda Arc, a chain of volcanic islands and trenches along the western edge of Indonesia. This type of convergent boundary is known as a subduction zone, where one plate is forced beneath the other and melted in the mantle, causing volcanic activity and earthquakes.

Question 15

A present day example of a continental-oceanic convergent plate boundary is

Accepted Answer

The Andes Mountains are formed by the subduction of the oceanic Nazca Plate beneath the continental South American Plate, making it a continental-oceanic convergent boundary.

Question 16

Which force may cause uplift, folding, and formation of reverse and thrust faults?

Accepted Answer

Compression is the force that causes uplift, folding, and formation of reverse and thrust faults.

Question 17

90 million years ago India was

Accepted Answer

90 million years ago, India was not part of Asia. It was a separate landmass that later collided with the Asian continent, leading to the formation of the Himalayan mountain range.

Question 18

All rift valleys extend sufficiently to form new continents and plate boundaries.

Accepted Answer

While rift valleys are associated with plate boundaries and can lead to the formation of new ocean basins, not all rift valleys extend enough to create new continents. The East African Rift Valley, for example, is not expected to result in the formation of a new continent.

Question 19

Figure 12.43 
-According to Figure 12.43 when did the Rocky Mountains form?

Accepted Answer

The Rocky Mountains primarily formed during the Laramide orogeny, which occurred around 50 million years ago.

Question 20

At convergent boundaries earthquake focal depths ________ with increasing distance from the trench.

Accepted Answer

At convergent boundaries, earthquake focal depths increase with increasing distance from the trench. This is because the descending lithosphere is gradually brought to a greater depth as it moves away from the trench and towards the subduction zone. This increase in depth also corresponds to an increase in pressure and temperature, which can cause the lithosphere to partially melt and trigger volcanic activity.

Quiz 12: Global Tectonics: Plates and Plumes