Question 1

Plate tectonics are unrelated to the rock cycle and,in fact,has made the rock-cycle concept obsolete.

Accepted Answer

Plate tectonics and the rock cycle are related processes that work together to shape the Earth's surface. Plate tectonics drive the rock cycle, as the movement of tectonic plates creates the conditions for the formation of various types of rocks through processes like weathering, erosion, deposition, and metamorphism. Therefore, the rock cycle concept remains relevant and useful in understanding how rocks are formed and transformed on Earth.

Question 2

Seawater interacting with hot sea floor at spreading ridges may produce mineral deposits.

Accepted Answer

Seawater interacting with hot sea floor at spreading ridges can contain dissolved minerals, which may precipitate out and form mineral deposits. These deposits can include sulfide minerals that contain valuable metals such as copper, zinc, and gold, among others. Such mineral deposits can form massive sulfide deposits, which have been mined on the ocean floor at hydrothermal vents.

Question 3

Although convection in the asthenosphere is widely accepted as the cause of plate movements,it may be that the weight of down-going lithosphere in subduction zones pulls the trailing plate behind it.

Accepted Answer

While convection in the asthenosphere is widely accepted as the cause of plate movements, the weight of down-going lithosphere in subduction zones can also contribute to the movements by pulling the trailing plate behind it. Therefore, the statement is true.

Question 4

Rifting occurs at oceanic spreading ridges,but not within continents,because continents are so thick and strong.

Accepted Answer

Rifting can occur within continents, such as the East African Rift Valley. The thickness and strength of continental crust do not necessarily prevent rifting from occurring.

Question 5

Satellite data now allow direct measurement of the rates of plate movement,even though it is slow.

Accepted Answer

Satellite data can directly measure the rates of plate movement, making it true that it is possible to measure even though it is a slow process.

Question 6

About 200 million years ago,most of the continents were together,forming a "super continent" called Pangaea.

Accepted Answer

This statement is true. Pangaea was a supercontinent that formed about 300 million years ago and began to break apart about 200 million years ago.

Question 7

Part of western California is attached to the Pacific Plate,while most of North America belongs to a separate plate.

Accepted Answer

This is true. Western California is located along the San Andreas Fault, which is the boundary between the Pacific Plate and the North American Plate. The Pacific Plate is slowly moving to the northwest while the North American Plate is moving to the southeast, causing frequent earthquakes in the region.

Question 8

Earthquakes occur at subduction zones,but volcanoes do not because the subducted lithosphere is pushed deep into the mantle.

Accepted Answer

Volcanoes often occur at subduction zones due to the melting of the subducting lithosphere as it sinks into the mantle, leading to the formation of magma that can erupt at the surface. Earthquakes also commonly occur at subduction zones as the subducting plate moves and interacts with the overriding plate.

Question 9

The Hawaiian Islands were formed by repeated volcanic eruptions over a hot spot.

Accepted Answer

The Hawaiian Islands were formed by repeated volcanic eruptions over a hot spot. As the Pacific Plate moved over the hot spot, it created a chain of islands that include the current eight main islands of Hawaii.

Question 10

The best explanation for the distribution of Glossopteris and Mesosaurus is that they lived when continents on which their fossils are now found were once connected then later were rifted and drifted apart.

Accepted Answer

The distribution of Glossopteris and Mesosaurus is consistent with the theory of continental drift, which explains how the continents were once connected in a supercontinent called Pangaea and later drifted apart. Fossils of Glossopteris are found in several continents that were once part of Gondwana, while fossils of Mesosaurus are found in South America and Africa, which were also once connected. This supports the idea that these organisms lived during a time when the continents were joined together and later separated due to tectonic forces.

Question 11

Transform faults that offset segments of a spreading ridge are formed because rates of spreading are not constant along any one rift zone so shearing develops when one segment grows faster than another.

Accepted Answer

Transform faults at spreading ridges occur due to differences in rates of spreading along the rift zone, resulting in shearing and offset segments. This is a result of the complex and dynamic nature of plate tectonics.

Question 12

It is not possible to estimate rates of plate movement because new rocks are constantly being created from old.

Accepted Answer

Plate movement can be estimated using various techniques such as GPS and satellite measurements, seismic activity, and studies of ancient magnetic field patterns in rocks. While new rocks are indeed constantly being created from old, there are ways to track and measure the movement of tectonic plates.

Quiz 3: Plate Tectonics