Question 1

Earth's inner core was discovered by seismologist

Accepted Answer

Inge Lehmann discovered Earth's inner core in 1936 by analyzing the seismic waves generated by earthquakes. Her observations of how these waves bounced off and traveled through Earth's core led to the conclusion that the Earth has a solid inner core distinct from its liquid outer core.

Question 2

The P wave shadow extends from roughly ___ to roughly ____ distance from an earthquake's focus.

Accepted Answer

The P wave shadow zone extends from roughly 100° to roughly 140° distance from an earthquake's focus, due to the refraction of seismic waves in the Earth's core.

Question 3

What sort of geothermal gradient is consistent with having convection in the mantle?

Accepted Answer

The answer of What sort of geothermal gradient is consistent...

Question 4

Let's assume that the inner core was liquid and the outer core was solid.What would one expect to see in terms of P and S wave shadows in terms of distance from an earthquake focus?

Accepted Answer

The S-wave shadow would start where the P-wave shadow ends because the S-waves would be refracted away from the liquid inner core, while the P-waves would be able to travel through it.

Question 5

Given that the P wave velocities are related to rock density,choose the sequence that shows the rocks in terms of increasing P wave speeds.Rock densities are: rock I = 2.9 gm/cc,rock II = 2.6 gm/cc,and rock III = 3.3 gm/cc.

Accepted Answer

P wave velocities increase with the density of the rock. Therefore, the sequence from lowest to highest density (and thus P wave speed) is rock II (2.6 gm/cc), rock I (2.9 gm/cc), and rock III (3.3 gm/cc).

Question 6

Recently scientists have suggested that __________,thus acting like a "planet within a planet."

Accepted Answer

The inner core spins faster than the mantle, which has led scientists to describe this phenomenon as the inner core acting like a "planet within a planet." This differential rotation is thought to influence Earth's magnetic field and has significant implications for understanding the planet's internal dynamics.

Question 7

Which portion of the mantle is relatively free of seismic discontinuities?

Accepted Answer

The answer of Which portion of the mantle is relatively...

Question 8

Over time,the size of the inner core will __________ and the size of the outer core will __________.

Accepted Answer

The inner core grows as it solidifies from the liquid outer core, which decreases in size as a result.

Question 9

Which of the following foods would best serve a proxy for Earth's layering?

Accepted Answer

A peach has a structure similar to Earth's layers, with a thin outer skin (crust), a fleshy part (mantle), and a hard pit (core).

Question 10

Calculations suggest that the inner core

Accepted Answer

Research indicates that Earth's inner core rotates slightly faster than the planet's surface and mantle, leading to the conclusion that it spins at a faster rate than the rest of Earth.

Question 11

Where,inside Earth,is the largest change in material density?

Accepted Answer

The core-mantle boundary represents the largest change in material density within Earth, as it marks the transition between the silicate mantle above and the metallic core below, involving a significant jump in density.

Question 12

Assume you are astronaut geophysicist working on Titan (Moon of Saturn)and measure a P-wave velocity of 8 km for the moon's crust.Assuming what you know from Earth,what kind of rock is this surface made of?

Accepted Answer

Peridotite is a type of rock that is found in the Earth's mantle and is composed of olivine and pyroxene. It is the most common type of rock on Earth and is also found on the Moon and Mars. The P-wave velocity of peridotite is typically around 8 km/s, which is consistent with the measured P-wave velocity of 8 km/s for the crust of Titan.

Question 13

In a deep mine,temperatures increase at the rate of approximately ______ per kilometer.

Accepted Answer

The geothermal gradient, which is the rate of temperature increase with respect to increasing depth in the Earth's interior, is typically about 25°C per kilometer in deep mines.

Question 14

Geologists have discovered a simple mathematical equation that relates the depth of the seafloor to crustal age.This relationship implies that the oceanic lithosphere

Accepted Answer

The relationship between seafloor depth and crustal age suggests that the oceanic lithosphere cools by conduction, as the seafloor depth increases with age due to thermal contraction as the lithosphere cools.

Question 15

Which of the following layers will not transmit S waves?

Accepted Answer

S waves, or secondary waves, are a type of shear wave that cannot travel through liquids. The outer core of the Earth is in a liquid state, which prevents the transmission of S waves through it.

Question 16

As seismic waves travel through Earth,they generally

Accepted Answer

Seismic waves generally curve upward due to the increase in speed as they travel through denser materials deeper within the Earth, causing them to refract and curve back towards the surface.

Question 17

The base of transition zone layer marks the beginning of the

Accepted Answer

The answer of The base of transition zone layer marks...

Question 18

According to the principle of isostasy

Accepted Answer

The answer of According to the principle of isostasy
...

Question 19

Geologists have formulated a simple mathematical equation that can predict the depth of oceans.According to their equation,on what does the water depth primarily depend?

Accepted Answer

The depth of the ocean primarily depends on the age of the seafloor. As the seafloor spreads away from mid-ocean ridges, it cools and sinks, making older seafloor deeper.

Question 20

Between 410 and 670 km depths,S-waves show several jumps attributed to phase changes in the upper mantle.What do geophysicists call this region?

Accepted Answer

The answer of Between 410 and 670 km depths,S-waves show...

Quiz 14: Exploring Earths Interior