Chapter 12 Seismology

Front 1

Vibrations that run along Earth's surface are called

Back 1

Surface Waves

Front 2

vibrations that propagate through Earth's interior are called

Back 2

Body Waves

Front 3

What 2 seismic waves can not pass through the core?

Back 3

S waves and surface waves

Front 4

The velocity of a seismic wave increases with what?

Back 4

the rigidity of the rock layer it is traveling through

Front 5

What data provided information about the existence of different zones within Earth?

Back 5

P-wave and S-wave arrival times

Front 6

Seismic waves move along curved ray paths because of what?

Back 6

the of changing properties of rocks

Front 7

Why do we believe Earth's outer core is a liquid?

Back 7

S waves do not travel through the outer core, also P waves slow down and refract at the boundary between the mantle and the outer core.

Front 8

Why do geologists believe the inner core is solid?

Back 8

P waves refract at the boundary between the outer core and inner core.

Front 9

How could you test whether the core of another planet were completely solid?

Back 9

Set off a bomb to create seismic waves. If S waves arrive on the opposite side of the planet, then the core is solid.

Front 10

Which layer of Earth possesses the greatest thickness?

Back 10

Mantle it makes up about 82% of the earth's volume

Front 11

What rock best represents the typical composition of oceanic crust?

Back 11

Basalt

Front 12

Which region of Earth is composed of abundant amounts of granite?

Back 12

Continental crust

Front 13

What is the major source of energy that drives the movements of the lithospheric plates on Earth?

Back 13

Thermal energy from within Earth, principally from the decay of radioactive elements, drives the movement of the lithospheric plates

Front 14

The magnetic field of Earth is thought to originate in what layer?

Back 14

Outer core

Front 15

What best describes why the lithospheric plates are able to move around on the surface of Earth?

Back 15

Because the asthenosphere is composed of weak, hot, and dense rock, the cold, rigid, less dense lithospheric plates are capable of moving on it.

Front 16

What describes the trend of the Earth’s temperature (based on the geotherm) moving toward the center of the Earth?

Back 16

Temperature increases with increasing depth but at different rates.

Front 17

Most rocks are cooler than the melting temperature of __________

Back 17

iron (shown by the geotherm and the iron melting curve)

Front 18

What does the iron melting curve tell us about the state of rocks in the Earth?

Back 18

hen the iron melting curve is to the left of the geotherm, rocks are molten. When the iron melting curve is to the right of the geotherm, rocks are solid.

Front 19

What layer contains mostly molten or liquid rock?

Back 19

Outer Core

Front 20

What 2 statements describe the relationship between the strengths of rocks and how close the temperature is to the melting point of iron?

Back 20

Rocks that are warm, or close to the melting point of iron, are weak and rocks that are cold, or further away from the melting point of iron, are strong.

Front 21

________ is a technique to view three-dimensional changes in composition and density by using seismology.

Back 21

Seismic tomography

Front 22

Which physical property is responsible for determining how Earth materials separate out into interior layers?

Back 22

density

Front 23

The ________ is a seismic boundary between the crust and the mantle where there is a dramatic increase in seismic wave velocity

Back 23

Moho Boundary

Front 24

What is the average geothermal gradient in the crust?

Back 24

30° C/km

Front 25

Short-lived radioactive isotopes are responsible for the heat generated in the interior today. True or false?

Back 25

False

Front 26

List the three compositionally distinct layers of earth's interior

Back 26

Mantle, outer core, inner core

Front 27

What causes a mineral phase change?

Back 27

When rocks are squeezed (pressure at around 300 to 400km)

Front 28

Mineral phase change

Back 28

A change that occurs when a mineral is subjected to intense pressure; in this change, the structure of a mineral may become unstable, causing its atoms to rearrange into a denser, more stable structure.

Front 29

Reflection (seismic)

Back 29

The redirection of some waves back to the surface when seismic waves hit a boundary between different Earth materials.

Front 30

wave refraction

Back 30

A change in direction of waves as they enter shallow water. The portion of the wave in shallow water is slowed, which causes the waves to bend and align with the underwater contours.

Front 31

Direct waves

Back 31

seismic waves that travel in a nearly straight path

Front 32

Moho

Back 32

boundary between the mantle and the crust

Front 33

The point at which both refracted waves and direct waves arrive at the same time is called what

Back 33

cross-over

Front 34

Shadow zone

Back 34

The zone between 105 and 140 degrees from an earthquake epicenter. Direct waves do not penetrate the shadow zone because of refraction by Earth's core.

Front 35

what seismic wave doesn't pass through liquids

Back 35

S waves

Front 36

Transition zone

Back 36

The lower portion of the upper mantle

Front 37

convection

Back 37

The transfer of heat in a fluid-like manner where hot materials displace cooler materials

Front 38

________ is the driving force of convection

Back 38

gravity

Front 39

viscosity

Back 39

water's resistance to flow

Front 40

Conduction

Back 40

the flow of heat through a material

Front 41

How is heat transferred to the inner most part of the earth to the outer part of the earth

Back 41

through covection

Front 42

Geotherm or geothermal gradient

Back 42

The profile of earth's average temperature at each depth

Front 43

What happens to rock as the geotherm approaches the rock's melting temperature

Back 43

The rock begins to soften and weaken. They become molten when the geotherm overlaps the melting temperature. (the viscosity increases with depth, due to pressure)

Front 44

Seismic tomography

Back 44

a technique for imaging Earth's sub-surface characteristics in an effort to understand deep geologic structure (it involves collecting signals from many different earthquakes)

Front 45

How is the earth really shaped

Back 45

oblate ellipsoid

Front 46

Is the force of gravity the same over earth's entire surface?

Back 46

No because the earth is not a perfect sphere the equator bulges out more then the north and south pole increasing distance from the earths core. The farther you are away from the core the less gravity their is. So therefor some one at the poles weighs less then someone at the equator

Front 47

What is thought to produce earth's magnetic field?

Back 47

Electrically charged and flowing Iron-rich fluid in the outer core is thought to generate the earth's magnetic field (a phenomenon know as the geodynamo)

Front 48

geodynamo

Back 48

The self-sustaining process responsible for maintaining the Earth's magnetic field in which the kinetic energy of covective motion of the Earth's liquid core is converted into magnetic energy.

Front 49

magnetosphere

Back 49

an atmospheric magnetic layer

Front 50

Phase change

Back 50

Transformation of one mineral to another

Front 51

What are the two main sources of heat in the earth's surface

Back 51

Radioactivity and kinetic energy left over from the amalgamation of the planet during the formation of the solar system

Front 52

The seismic boundary between the crust and the mantle is referred to as the __________.

Back 52

Mohorovicic discontinuity (Moho)

Front 53

Approximately how deep is Earth's core–mantle boundary?

Back 53

2900km

Front 54

How does the rotational speed of the inner core compare with the rest of the planet?

Back 54

Perhaps a century or more faster

Front 55

__________ is the transfer of heat by the mass movement or circulation in a substance.

Back 55

Convection

Front 56

The source of heat that produces deep mantle plumes is believed to be located at the __________.

Back 56

outer core–mantle boundary (D)

Front 57

Which is Earth's weakest layer?

Back 57

Asthenosphere

Front 58

The greatest change in the velocity of P waves occurs at the __________ boundary.

Back 58

mantle–outer core

Front 59

Shadow zone

Back 59

The zone between 105 and 140 degrees from an earthquake epicenter. Direct waves do not penetrate the shadow zone because of refraction by Earth's core.

Front 60

Which of Earth's major divisions is thought to be the source of the magnetic field?

Back 60

outer core

Front 61

What layer is composed of the crust plus the uppermost mantle?

Back 61

lithosphere

Front 62

This layer averages only about 7 kilometers (5 miles) in thickness.

Back 62

oceanic crust

Front 63

This thick shell of rock is composed mostly of silicate minerals that are rich in iron and magnesium.

Back 63

Mantle