Question 1

Which of the following will NOT be a consequence of Earth's consumption of the bulk of its radioactive "fuel" in the future?

Accepted Answer

The answer of Which of the following will NOT be...

Question 2

Which of the following statements is FALSE?

Accepted Answer

There is currently no evidence of liquid water flowing on the surface of Mars. The polar ice caps do contain water ice, but it does not melt and flow in liquid form during summer.

Question 3

The observation that the Moon's average density is similar to the density of the Earth's _________ supports the collision theory of the Moon's origin.

Accepted Answer

The Moon's average density is similar to that of the Earth's mantle, supporting the collision theory, which suggests that the Moon formed from debris resulting from a collision between the Earth and a Mars-sized body, primarily involving the Earth's outer layers.

Question 4

In the Earth's crust, lower density igneous rock such as _________ make up the continents, and higher density volcanic rock such as _________ make up the ocean floor.

Accepted Answer

Granite is a lower density igneous rock that forms the continents, while basalt is a higher density volcanic rock that makes up the ocean floor. Limestone, sandstone, marble, and iron-rich silicates do not have the same density or geological locations as granite and basalt.

Question 5

Differentiation refers to materials that are separate based on their:

Accepted Answer

Differentiation involves separation based on density, which is the ratio of mass to volume. Therefore, option D is the correct choice. Weight, mass, volume, and heat capacity are all properties of a substance, but they are not relevant to differentiation.

Question 6

What is the main reason that the Earth's interior is liquid today?

Accepted Answer

The decay of radioactive elements generates heat, which contributes to keeping parts of the Earth's interior in a liquid state.

Question 7

Based on the assumption that a liquid, conducting core and rapid rotation are both required for a magnetic dynamo to operate, which terrestrial planets would you expect to have magnetic fields?

Accepted Answer

The answer of Based on the assumption that a liquid,...

Question 8

Figure 3
-Which layer in Figure 3 represents the Earth's liquid mantle?

Accepted Answer

Layer B represents the Earth's liquid mantle, which is the layer of molten rock located between the Earth's crust and core. Layer A is the Earth's crust, layer C is the Earth's outer core, and layer D is the Earth's inner core.

Question 9

Earth's innermost core is solid, not liquid, because:

Accepted Answer

The pressure at the Earth's inner core is incredibly high, estimated to be around 3.5 million times atmospheric pressure at sea level. This pressure is so great that it prevents the iron from melting, which would result in a liquid state. Therefore, the Earth's innermost core remains solid.

Question 10

What will eventually happen to the Earth when radioactive decays in its interior cease?

Accepted Answer

When radioactive decay ceases, the Earth's interior will cool, leading to the solidification of the core, cessation of continental drift and earthquakes, and a decrease in the magnetic field strength.

Question 11

Suppose an earthquake occurs on an imaginary planet. Scientists on the other side of the planet detect primary waves but not secondary waves after the quake occurs. This suggests that:

Accepted Answer

The fact that only primary waves (P-waves) are detected suggests that the waves are traveling through solid rock, but the absence of secondary waves (S-waves) suggests that there is a layer of liquid in the planet's interior. S-waves cannot travel through liquid, so their absence would indicate the presence of a liquid layer in the planet's interior.

Question 12

If you obtained a sample of rock from Venus and determined the abundances of uranium (²³⁸U) and lead (²⁰⁷Pb) in it, and found that for every one uranium atom there were three lead atoms, then what would the age of this rock be? Note that this form of uranium decays to this form of lead with a half-life of 700 million years. For simplicity, you can assume that there was no lead in the rock when it originally formed.

Accepted Answer

The answer of If you obtained a sample of rock...

Question 13

Consider an external solar system in which there are three terrestrial planets. All are located far from other objects so tidal forces aren't significant. If planet A has a radius of 1 Earth radius, and planet B has a radius of 2 Earth radii, and planet C has a radius of 3 Earth radii, which planet has the highest chance of having at least a partially liquid core and a detectable magnetic field?

Accepted Answer

Larger planets like Planet C are more likely to retain internal heat, which can keep their cores partially liquid and generate a magnetic field.

Question 14

The fact that Earth's interior is differentiated suggests that:

Accepted Answer

Differentiation implies that Earth was once entirely liquid, allowing denser materials to sink to the center and lighter materials to rise, forming distinct layers.

Question 15

Which of the following is NOT a requirement for a planetary magnetic dynamo?

Accepted Answer

A solid iron core cannot undergo convective motions, which are necessary for the generation of a planetary magnetic dynamo. Therefore, a requirement for a planetary magnetic dynamo is a liquid interior. Rapid rotation, convective motions, charged particles in the interior, and a liquid interior are all necessary for the generation of a planetary magnetic dynamo.

Question 16

Figure 3
-Which layer in Figure 3 represents the Earth's liquid core?

Accepted Answer

Layer C represents the Earth's liquid outer core, which is composed primarily of iron and nickel.

Question 17

The dynamo theory says that a planet will have a strong magnetic field if it has:

Accepted Answer

The dynamo theory states that a planet's magnetic field is generated by convective motions in its liquid, rotating metallic core. Therefore, a planet would have a strong magnetic field if it has a liquid core that rotates quickly. So, the correct choice is C: fast rotation and a liquid core.

Question 18

Mars has a diameter that is approximately half that of Earth's. If the interiors of these planets are heated by radioactive decays, how does the heating rate of Mars' interior compare to that of Earth's?

Accepted Answer

The heating rate depends on the volume-to-surface area ratio. Mars has a smaller volume relative to its surface area compared to Earth, leading to a lower heating rate, approximately 0.125 times that of Earth's.

Question 19

If you obtained a sample of a meteorite and determined the abundances of uranium (²³⁸U) and lead (²⁰⁷Pb) in it, and found that for every 1 uranium atom there were 15 lead atoms, then what would the age of this rock be? Note that this form of uranium decays to this form of lead with a half-life of 700 million years. For simplicity, you can assume that there was no lead in the rock when it originally formed.

Accepted Answer

The ratio of 1 uranium atom to 15 lead atoms suggests that 4 half-lives have passed (since 1:15 implies 1 part uranium to 15 parts lead, meaning 16 total parts, which is 2^4). Each half-life is 700 million years, so 4 half-lives is 2.8 billion years.

Question 20

The Moon has a diameter that is approximately one-fourth that of Earth. If these objects' interiors are heated by radioactive decays, and the total amount of energy in decays is proportional to the object's volume, then how does the amount of heat the Moon has compare to that of Earth?

Accepted Answer

The energy in decays is proportional to volume. Since the Moon's diameter is one-fourth that of Earth's, its volume is 1/64 of Earth's volume (since volume scales as diameter cubed). Therefore, if the energy from decays is proportional to the object's volume, then the Moon's heating rate is 1/64 that of Earth's. In other words, the Moon has 0.016 times the heating rate of Earth. So the answer is A).

Quiz 8: The Terrestrial Planets and Earths Moon