Question 1

The magnetic orientation and age of different regions of the seafloor is inferred from the total field intensity using towed magnetometers.

Accepted Answer

This statement is true. The magnetic orientation and age of different regions of the seafloor can be inferred by measuring the total field intensity using towed magnetometers. As seafloor spreading occurs, new crust is formed and the magnetic minerals in the lava align with the Earth's magnetic field at the time of formation. This creates patterns of magnetization that can be detected and used to determine the age of the ocean floor and the direction of the Earth's magnetic field at the time of formation.

Question 2

In detail, there is no geologic evidence that mid-ocean ridges spread at uniform rates or even symmetrically.

Accepted Answer

Mid-ocean ridges spread at rates that can be measured and have been found to spread symmetrically in many cases, as evidenced by the symmetric pattern of magnetic stripes on either side of the ridges, which record reversals of the Earth's magnetic field.

Question 3

Which of the following most accurately describes the volcanoes of the Hawaiian Islands?

Accepted Answer

The Hawaiian Islands are located on a hot spot, which is a stationary magma source that produces magma that rises through the Pacific plate and forms shield volcanoes.

Question 4

Which of the following energy sources is thought to directly drive the lateral motions of Earth's lithospheric plates?

Accepted Answer

The export of heat from deep in the mantle to the top of the asthenosphere and descending cold material in a solid-state convective flow is the most widely accepted energy source thought to directly drive the lateral motions of Earth's lithospheric plates. This process is known as mantle convection and involves the movement of heat and material through the mantle, which drags the overlying lithospheric plates along with it. Tidal gravitational attractive forces of the Sun and Moon can affect the velocity of plate motion, but they do not directly drive it. Electric and magnetic fields generated in and radiating from the inner core do not have a well-established link to plate motion, and the rotational spinning of the Earth plays a role in the overall behavior of the planet but is not the primary energy source driving plate motion.

Question 5

Early results of the Deep Sea Drilling Program clearly justified the conclusion that ________.

Accepted Answer

The early results of the Deep Sea Drilling Program showed that most ocean basin rocks and sediments are Cretaceous or younger in age, indicating that the ocean basins are relatively young. This finding clearly justified this conclusion. Option A is incorrect, as the program did not provide evidence for or against the idea that the oceans have always contained most of Earth's water. Option C is incorrect because the program found Proterozoic rocks in places other than just the deepest parts of the ocean basins. Option D is incorrect because the program did not find evidence of the youngest sediments being deposited directly on the oldest seafloor basalts.

Question 6

Early results of the Deep Sea Drilling Project clearly justified the conclusion that ________.

Accepted Answer

The early results of the Deep Sea Drilling Project showed that ocean basins are geologically young, with those closer to the ridges being even younger. This supported the theory of plate tectonics, which proposed that new oceanic crust is continuously being formed at mid-ocean ridges, pushing the older crust away from the ridge.

Question 7

What span of seafloor motion is recorded by the hot spot track of the Hawaii-Emperor seamount chain?

Accepted Answer

The hot spot track of the Hawaii-Emperor seamount chain records seafloor motion over a span of 0-65 million years, reflecting the movement of the Pacific Plate over a stationary hot spot in the Earth's mantle.

Question 8

All of the following are evidence supporting the theory of plate tectonics except for ________.

Accepted Answer

Changes in the Moon's orbit are not considered evidence for plate tectonics. While plate tectonics can indirectly affect the Moon's orbit through changes in Earth's mass distribution, this is not considered direct evidence for the theory. B, C, and D are all examples of evidence that support plate tectonics. Ocean floor drilling provides evidence of seafloor spreading and the age of the oceanic crust, hot spots are evidence of plate motion over fixed mantle plumes, and measurements of plate motions provide direct evidence of the movement of tectonic plates.

Question 9

During various times in the geologic past, the polarity of Earth's magnetic field has been reversed.

Accepted Answer

Geologic evidence shows that the Earth's magnetic field has gone through numerous reversals in the past, where the magnetic north and south poles switch places. These reversals are recorded in rocks and sediments, and are an important tool for geochronology and understanding the history of the planet.

Question 10

In the nomenclature of J.Tuzo Wilson, a very long-lived magma source rising from deep in the mantle is called a(n)________.

Accepted Answer

J. Tuzo Wilson referred to a very long-lived magma source rising from deep in the mantle as a hot spot. This term is still widely used in geology today to describe areas of volcanic activity that are not associated with plate boundaries.

Question 11

Wegener's continental drift hypothesis was unanimously accepted by the international scientific community when he proposed it.

Accepted Answer

While Wegener proposed the continental drift hypothesis in 1912, it was not unanimously accepted by the international scientific community. In fact, for decades afterwards, many scientists were skeptical of the idea and it wasn't until the 1950s and 1960s when new evidence emerged in the fields of plate tectonics and paleomagnetism that the theory gained widespread acceptance.

Question 12

What is the cause of the magmas currently erupting in the Hawaiian Islands?

Accepted Answer

The magmas currently erupting in the Hawaiian Islands are caused by shallow decompression melting of a fixed mantle plume, with magmas rising through the NW-moving Pacific plate.

Question 13

The "big bend" in the Hawaii-Emperor seamount chain occurred at about 45 million years ago.What is the most likely explanation for this change in the orientation of the hot spot track across the Pacific plate?

Accepted Answer

The change in the orientation of the hot spot track can be explained by the shift in subduction from the Aleutian trench to the Kurile-Kamchatka trench, which caused the Pacific plate to change direction from moving northwards to moving northwest. This change in plate motion caused the hot spot track to shift and bend towards the southeast. Choice B is incorrect because hot spots are typically stationary and do not abruptly change direction. Choice C is also incorrect because there is no evidence to support the existence of two unrelated hot spot tracks intersecting at the big bend. Choice D is a nonsensical and unscientific explanation.

Question 14

What kind of geologic studies were the primary focus of the Glomar Challenger and JOIDES Resolution's international investigations?

Accepted Answer

The Glomar Challenger and JOIDES Resolution were research vessels primarily focused on drilling the seafloor sediments and underlying ocean crust to study the history and development of different oceanic regions. This was done through the International Ocean Discovery Program (IODP) which aimed to investigate Earth's interconnected systems and understand global processes through ocean drilling.

Question 15

Which of the following is not part of the accepted driving mechanism of plate tectonic motions?

Accepted Answer

The statement that all of the heat for mantle convection comes from small amounts of radioactive elements in the inner core is incorrect. While radioactive elements do contribute to the heat budget of the Earth's interior, it is not the sole source of heat driving mantle convection. Other sources include residual heat from the planet's formation, heat released by ongoing chemical reactions in the mantle, and heat transfer from the core.

Question 16

Anywhere in the world, ________ most effectively outline the edges of the lithospheric plates.

Accepted Answer

Lines of earthquake epicenters are the most effective way to outline the edges of lithospheric plates as earthquakes occur at plate boundaries where tectonic forces are most active.

Question 17

Evidence for the supercontinent Pangaea includes fit of continents, matching fossils and mountain chains separated by ocean basins, and ancient glaciated rocks in the southern hemisphere.

Accepted Answer

The fit of continents, matching fossils and mountain chains separated by ocean basins, and ancient glaciated rocks in the southern hemisphere all provide evidence for the existence of the supercontinent Pangaea.

Question 18

Deep-hypocentre earthquakes are associated with ________ plate boundaries.

Accepted Answer

Deep-hypocentre earthquakes occur at convergent plate boundaries, specifically where one tectonic plate is subducting beneath another. This is because the subducting plate is being forced deep into the mantle, where the high pressure and temperature allows for seismic activity to occur at great depths.

Question 19

What is the most likely explanation for why there are no islands, only deep seamounts and guyots NW of Kauai towards Midway?

Accepted Answer

Over time, older seafloor farther from the current hot spot cools and sinks, causing the volcanoes to erode and sink below sea level. This is the most likely explanation for why there are no islands, only deep seamounts and guyots NW of Kauai towards Midway.

Question 20

The magnetic inclination of a lava flow that originally cooled near the equator is shallow.

Accepted Answer

The magnetic inclination of a lava flow that originally cooled near the equator is shallow because the magnetic field lines near the equator are nearly parallel to the Earth's surface. This causes the magnetic inclination to be close to zero.

Quiz 12: Plate Tectonics: The Framework for Modern Geology