Question 1

Which of the following is true of Earth's crust?

Accepted Answer

The ocean floor is mostly made up of basaltic rocks that are younger than the continental crust. The oceanic crust is constantly being formed at mid-ocean ridges and is much thinner (5-10 km) than the continental crust (35-40 km).

Answer: B
 The Earth's crust is divided into multiple plates that move relative to each other. These plates are either continental or oceanic and can interact with each other at boundaries like divergent, convergent, and transform.

Answer: C
 The Earth's crust is the thinnest layer of the Earth, with an average thickness of 30 km below the continents and 5-10 km below the oceans. The mantle is the thickest layer, making up about 84% of the Earth's volume.

Answer: D
 The Earth's crust and outer core have very different compositions. The crust is primarily made up of silicate rocks, while the outer core is composed mostly of iron and nickel.

Question 2

How would the surface of Earth change if its deep interior had no radioactive elements?

Accepted Answer

Radioactive elements in Earth's deep interior are a driving force behind plate tectonics, which is responsible for shaping the surface of the planet. Without these elements, there would be no plate tectonics, and the Earth's surface would be vastly different.

Answer: B
 Radioactive elements can be harmful to life, and their absence could make the Earth's surface more hospitable for living organisms.

Answer: D
 While the absence of radioactive elements would have significant impacts on the deep interior of the Earth, it may not result in significant changes to the surface. The surface of the Earth is affected by a variety of forces, and the absence of radioactive elements may not be the most dominant factor.

Therefore, the answer depends on what is considered a significant change to the surface of the Earth.

Question 3

An atomic nucleus that transforms from one element to another has undergone:

Accepted Answer

A change in the element of the nucleus implies a change in its atomic number, which occurs during radioactive decay. Ionization refers to the removal or addition of electrons from an atom, while excitation involves the temporary increase in energy levels of an atom or nucleus. Scattering refers to the redirection of particles after a collision.

Question 4

The layer of Earth shown in the figure below is called the:

Accepted Answer

The layer shown in the figure is the mantle. It is the layer of Earth between the crust and the core.

Question 5

The wave shown in the figure below is most similar to a(n):

Accepted Answer

The answer of The wave shown in the figure below...

Question 6

A long line of active volcanoes often marks:

Accepted Answer

A long line of active volcanoes often marks the boundary of two plates, where one plate is being subducted beneath another, leading to magma formation and volcanic activity.

Question 7

Our understanding of Earth's interior comes primarily from:

Accepted Answer

Our understanding of Earth's interior comes primarily from earthquakes, as seismic waves reveal information about the structure and composition of the planet's layers. Deep drilling and volcanoes can also provide insight, but earthquakes are the most important source of information. Magnetism is important for studying the magnetic field and its variations, but not as much for understanding the interior structure.

Question 8

Which of the following sequences correctly characterizes the composition of Earth's layers,from its center to its surface?

Accepted Answer

The Earth's layers, from its center to its surface, are composed of a solid iron inner core, a molten iron outer core, and a mantle made of silicate rocks.

Question 9

Which moon in the Solar System has the largest mass relative to the planet it orbits?

Accepted Answer

The Moon has the largest mass relative to Earth compared to any other moon's mass relative to its planet in the Solar System. This unique ratio significantly influences Earth's tides and contributes to the stability of its axial tilt.

Question 10

Which layers of Earth transport heat primarily through the bulk motion of material?

Accepted Answer

The outer core and mantle both transport heat primarily through the bulk motion of material, in the form of convection. The inner core is solid and does not participate in convection, and the crust is too thin to play a significant role in heat transport.

Question 11

The ultimate power source of plate tectonics comes from:

Accepted Answer

The ultimate power source of plate tectonics is the heat produced by radioactive decay within the Earth's mantle, which drives convection currents that move the plates.

Question 12

A meteor contains fifteen times as much argon-40 as potassium-40.If the half-life of potassium-40 is 1.25 billion years,how long ago did the meteor form?

Accepted Answer

The answer of A meteor contains fifteen times as much...

Question 13

When a cup of coffee cools through rising and falling motions of the fluid,we say it undergoes:

Accepted Answer

The rising and falling motions of the fluid are caused by differences in temperature and density in the cup of coffee. This process of heat transfer through the movement of fluids is called convection.

Question 14

Which of the following is NOT a common result of the collision of two plates?

Accepted Answer

Mid-ocean ridges are typically formed from the divergence of two plates, not their collision. Therefore, it is not a common result of plate collision.

Question 15

If Earth's Moon were less massive,which of the following would be most likely to occur?

Accepted Answer

A less massive Moon would exert a weaker gravitational pull on Earth, potentially affecting the stability of Earth's axial tilt. The axial tilt is crucial for the seasonal climate patterns we experience; a more variable tilt could lead to a less stable climate. Choices B, C, and D do not directly relate to the mass of the Moon affecting Earth's orbit, the frequency of solar eclipses, or the Moon's rotation speed in a manner described.

Question 16

The Hawaiian Islands provide evidence for:

Accepted Answer

The Hawaiian Islands are formed by a series of shield volcanoes that were formed by mantle plumes originating from the Earth's mantle. This process is a result of mantle convection, which drives the movement of tectonic plates and leads to sea-floor spreading. Therefore, the Hawaiian Islands provide evidence for all three processes: mantle plumes, sea-floor spreading, and mantle convection.

Question 17

The refraction of P-waves in the mantle is due to:

Accepted Answer

Refraction of P-waves in the mantle is mainly caused by changes in the density of materials at different depths, which results in the bending of the waves. This is known as the velocity discontinuity or the Lehmann Discontinuity, located at the boundary between the upper and lower mantle. The mantle is mostly solid, so A (the semimolten state of the mantle) and B (convection) are not the primary causes of P-wave refraction. D (radioactive decays) is also not a direct cause of wave refraction.

Question 18

Uranium-238 undergoes radioactive decay with a half-life of 4.5 billion years,producing lead-206.After 13.5 billion years,what is the ratio of uranium-238 to lead-206 in a sample that originally contained only uranium-238?

Accepted Answer

After 4.5 billion years, half of the uranium-238 would have decayed into lead-206. After another 4.5 billion years, half of the remaining uranium-238 would decay, leaving 25% uranium-238 and 75% lead-206. After another 4.5 billion years, half of the remaining uranium-238 would decay again, leaving 12.5% uranium-238 and 87.5% lead-206. Finally, after a total of 13.5 billion years, we have gone through three half-lives, so the ratio of uranium-238 to lead-206 is 1:7. Therefore, the correct answer is D, which has a 1:8 ratio.

Question 19

Suppose that a major earthquake occurs in southern California.A seismograph on the opposite side of Earth would see:

Accepted Answer

P-waves, or primary waves, can travel through both liquids and solids, allowing them to be detected on the opposite side of the Earth after an earthquake. S-waves, or secondary waves, cannot travel through the liquid outer core of the Earth, so they are not detected on the opposite side of the planet.

Question 20

A shield volcano is most likely to be associated with a(n):

Accepted Answer

Shield volcanoes are typically associated with mantle plumes, which are columns of hot material rising from deep within the Earth's mantle. As this hot material reaches the surface, it produces a large, broad volcano with gently sloping sides. These volcanoes tend to be relatively quiet and non-explosive, with lava flows that can be extensive and long-lasting. While shield volcanoes can sometimes occur near plate boundaries or subduction zones, they are most commonly associated with mantle plumes.

Quiz 6: Home Base: Earth and Moon