Question 1

Which one of the following is an important fundamental assumption underlying the plate tectonic theory?

Accepted Answer

The plate tectonic theory assumes that the Earth's diameter has been essentially constant over time. This is because the movement of tectonic plates is constrained by the size of the Earth; if the Earth were expanding or contracting, the movement of the plates would not be consistent with what has been observed. The other options are not fundamental assumptions of the plate tectonic theory.

Question 2

________ was never proposed as evidence supporting the existence of Pangaea.

Accepted Answer

Islands of Proterozoic rocks along the Mid-Atlantic Ridge were not proposed as evidence supporting the existence of Pangaea. The other choices were widely accepted as evidence for the existence of Pangaea by the scientific community.

Question 3

Following technologic advances in ocean mapping that came from the Cold War in the 1950s and 1960s the new data from the ocean basins led ________ to propose the first model for seafloor spreading.

Accepted Answer

Harry Hess proposed the first model for seafloor spreading after analyzing data from the ocean basins that were obtained during the Cold War era. Sir Edward Bullard, Keith Runcorn, and Alfred Wegener made significant contributions to the field of geology, but they did not propose the first model for seafloor spreading.

Question 4

Linear, magnetic patterns associated with mid-ocean ridges are configured as ________.

Accepted Answer

Linear, magnetic patterns associated with mid-ocean ridges are configured as normal and reversed magnetized stripes roughly parallel to the ridge. These magnetic patterns are caused by the periodic reversal of Earth's magnetic field, and they are recorded in the rock of the ocean floor as it spreads away from the ridge. This phenomenon is known as seafloor spreading and is a key piece of evidence supporting the theory of plate tectonics.

Question 5

What does the plate reconstruction, with the Atlantic Ocean closed up, do to the apparent polar wandering paths for Eurasia and North America, and what can we infer from this?

Accepted Answer

If the Atlantic Ocean is closed up, Eurasia and North America appear to fit together, indicating that they were once connected. The fact that their apparent polar wandering paths coincide suggests that the opening of the Atlantic Ocean was the cause of their divergence.

Question 6

Wegener's supercontinent that began to break up about 200 million years ago was named ________.

Accepted Answer

The supercontinent that began to break up about 200 million years ago and was named by Wegener was Pangaea. A is incorrect, as Gondwanaland was a separate southern supercontinent that formed from the breakup of Pangaea. B is incorrect, as Laurasia was a separate northern supercontinent that formed from the breakup of Pangaea. D is incorrect, as Rodinia was a much earlier supercontinent that formed about 1 billion years ago and began to break up about 750 million years ago.

Question 7

What was the unexpected contribution of Keith Runcorn and his students to the continental drift controversy?

Accepted Answer

Keith Runcorn and his students contributed the concept of apparent polar wander paths, which provided evidence that the magnetic pole or the continent's position had wandered with time. This evidence supported the theory of continental drift.

Question 8

________ first related the symmetrical magnetic patterns in seafloor basalts to seafloor spreading at a mid-ocean ridge.

Accepted Answer

Morley, Vine, and Matthews were the first to relate the symmetrical magnetic patterns in seafloor basalts to seafloor spreading at a mid-ocean ridge.

Question 9

New oceanic crust and lithosphere are formed at ________.

Accepted Answer

New oceanic crust and lithosphere are formed at divergent boundaries by submarine eruptions and intrusions of mafic magma. Divergent boundaries are areas where the Earth's tectonic plates move away from each other. Mafic magma is low in silica and high in magnesium and iron, which makes it more fluid and easier for it to flow to the surface to form new crust.

Question 10

________ discovered transform faults and first proposed that Earth's outer shell comprises several rigid plates.

Accepted Answer

Tuzo Wilson discovered transform faults and was the first to propose the theory of plate tectonics, which states that Earth's outer shell is divided into several rigid plates that move and interact with each other. Charles Darwin was an evolutionary biologist, James Hutton was a geologist who proposed the theory of uniformitarianism, and Harry Hess was a geologist who proposed the theory of seafloor spreading.

Question 11

The top of the asthenosphere is closest to the surface ________.

Accepted Answer

The asthenosphere is located just beneath the lithosphere, which includes the Earth's crust and the uppermost part of the mantle. Along a mid-ocean ridge, the lithosphere is spreading apart, and the asthenosphere is closer to the surface, making it a good choice for the answer. Along the length of a deep mantle plume or a subduction zone, the lithosphere is being pushed down into the mantle, making the asthenosphere farther from the surface. Along a transform fault, the lithosphere is sliding past each other, but there is typically no significant change in depth to the asthenosphere.

Question 12

What is the inclination of Earth's magnetic field as recorded in a recent lava flow on a volcano in northern Peru?

Accepted Answer

The inclination of Earth's magnetic field in northern Peru, as recorded in a recent lava flow, would be nearly horizontal and pointing north due to the location's proximity to the magnetic equator.

Question 13

How can you tell from the apparent polar wandering curves for Eurasia and North America, when they were last together and had just started to drift apart?

Accepted Answer

The apparent polar wandering curves for Eurasia and North America show parallel paths and maintain a consistent distance apart for times older than 200 million years, indicating that the continents were together and started to drift apart around that time.

Question 14

The former, late Paleozoic super continent is known as ________.

Accepted Answer

The former, late Paleozoic super continent is known as Pangaea.

Question 15

What is the inclination of Earth's magnetic field as recorded in a recent lava flow near 59 degrees north in Yukon?

Accepted Answer

At 59 degrees north, the Earth's magnetic field is steeply inclined and generally points towards the magnetic north.

Question 16

In the early part of the 20th century, ________ argued forcefully for continental drift.

Accepted Answer

Alfred Wegener argued for continental drift in the early part of the 20th century.

Question 17

Where is the inclination of Earth's magnetic field the steepest?

Accepted Answer

The inclination of Earth's magnetic field is the steepest at the North and South poles, where the magnetic lines of force are nearly vertical. At the equator, they are almost parallel to the surface, so the inclination is shallower. The latitudes between 45 and 50 degrees experience moderate inclination angles. The Bermuda triangle is not relevant to the inclination of Earth's magnetic field.

Question 18

How does the polar wander curve for Eurasia confirm Wegener's hypothesis that the Carboniferous (300 million years ago)coal beds were originally deposited when that land mass was near the equator?

Accepted Answer

The polar wander curve for Eurasia shows that to restore the 300 million year paleopole (magnetic pole) to today's north magnetic pole would require Eurasia to be pushed approximately 40 degrees of latitude farther south than it is today. This means that at that time, Eurasia was closer to the equator and supports Wegener's hypothesis that the 300 million year old coal beds were originally deposited when that land mass was near the equator. Choice B is incorrect because the steep magnetic inclination of the coal beds does not necessarily confirm the equatorial position of Eurasia at the time of their deposition. Choice C is incorrect because the polar wander curve does not suggest that Eurasia was in the middle of the north Pacific Ocean 300 million years ago, and choice D is incorrect because the switch of the equator and magnetic pole positions does not necessarily mean that Eurasia was tropical at that time.

Question 19

Where is the inclination of Earth's magnetic field horizontal?

Accepted Answer

The inclination of Earth's magnetic field is horizontal at the equator.

Question 20

What do the data points signify on the apparent polar wandering curves for Eurasia and North America?

Accepted Answer

The data points on the apparent polar wandering curves for Eurasia and North America represent the apparent positions for the north magnetic pole at various times in the past, based on paleomagnetic measurements on different rock sequences in Eurasia and North America.

Quiz 12: Plate Tectonics: The Framework for Modern Geology