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63 Cards in this Set
- Front
- Back
Vibrations that run along Earth's surface are called |
Surface Waves |
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vibrations that propagate through Earth's interior are called |
Body Waves |
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What 2 seismic waves can not pass through the core? |
S waves and surface waves |
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The velocity of a seismic wave increases with what? |
the rigidity of the rock layer it is traveling through |
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What data provided information about the existence of different zones within Earth? |
P-wave and S-wave arrival times |
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Seismic waves move along curved ray paths because of what? |
the of changing properties of rocks |
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Why do we believe Earth's outer core is a liquid? |
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.
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Why do geologists believe the inner core is solid? |
P waves refract at the boundary between the outer core and inner core. |
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How could you test whether the core of another planet were completely solid? |
Set off a bomb to create seismic waves. If S waves arrive on the opposite side of the planet, then the core is solid. |
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Which layer of Earth possesses the greatest thickness? |
Mantle it makes up about 82% of the earth's volume |
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What rock best represents the typical composition of oceanic crust? |
Basalt |
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Which region of Earth is composed of abundant amounts of granite? |
Continental crust |
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What is the major source of energy that drives the movements of the lithospheric plates on Earth? |
Thermal energy from within Earth, principally from the decay of radioactive elements, drives the movement of the lithospheric plates |
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The magnetic field of Earth is thought to originate in what layer? |
Outer core |
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What best describes why the lithospheric plates are able to move around on the surface of Earth? |
Because the asthenosphere is composed of weak, hot, and dense rock, the cold, rigid, less dense lithospheric plates are capable of moving on it. |
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What describes the trend of the Earth’s temperature (based on the geotherm) moving toward the center of the Earth? |
Temperature increases with increasing depth but at different rates. |
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Most rocks are cooler than the melting temperature of __________ |
iron (shown by the geotherm and the iron melting curve) |
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What does the iron melting curve tell us about the state of rocks in the Earth? |
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. |
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What layer contains mostly molten or liquid rock? |
Outer Core |
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What 2 statements describe the relationship between the strengths of rocks and how close the temperature is to the melting point of iron? |
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. |
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________ is a technique to view three-dimensional changes in composition and density by using seismology. |
Seismic tomography |
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Which physical property is responsible for determining how Earth materials separate out into interior layers? |
density |
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The ________ is a seismic boundary between the crust and the mantle where there is a dramatic increase in seismic wave velocity |
Moho Boundary |
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What is the average geothermal gradient in the crust? |
30° C/km |
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Short-lived radioactive isotopes are responsible for the heat generated in the interior today. True or false? |
False |
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List the three compositionally distinct layers of earth's interior |
Mantle, outer core, inner core |
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What causes a mineral phase change? |
When rocks are squeezed (pressure at around 300 to 400km) |
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Mineral phase change |
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. |
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Reflection (seismic) |
The redirection of some waves back to the surface when seismic waves hit a boundary between different Earth materials. |
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wave refraction |
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. |
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Direct waves |
seismic waves that travel in a nearly straight path |
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Moho |
boundary between the mantle and the crust |
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The point at which both refracted waves and direct waves arrive at the same time is called what |
cross-over |
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Shadow zone |
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. |
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what seismic wave doesn't pass through liquids |
S waves |
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Transition zone |
The lower portion of the upper mantle |
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convection |
The transfer of heat in a fluid-like manner where hot materials displace cooler materials |
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________ is the driving force of convection |
gravity |
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viscosity |
water's resistance to flow |
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Conduction |
the flow of heat through a material |
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How is heat transferred to the inner most part of the earth to the outer part of the earth |
through covection |
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Geotherm or geothermal gradient |
The profile of earth's average temperature at each depth |
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What happens to rock as the geotherm approaches the rock's melting temperature |
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) |
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Seismic tomography |
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) |
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How is the earth really shaped |
oblate ellipsoid |
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Is the force of gravity the same over earth's entire surface? |
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 |
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What is thought to produce earth's magnetic field? |
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) |
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geodynamo |
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. |
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magnetosphere |
an atmospheric magnetic layer |
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Phase change |
Transformation of one mineral to another |
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What are the two main sources of heat in the earth's surface |
Radioactivity and kinetic energy left over from the amalgamation of the planet during the formation of the solar system |
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The seismic boundary between the crust and the mantle is referred to as the __________. |
Mohorovicic discontinuity (Moho) |
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Approximately how deep is Earth's core–mantle boundary? |
2900km |
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How does the rotational speed of the inner core compare with the rest of the planet? |
Perhaps a century or more faster |
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__________ is the transfer of heat by the mass movement or circulation in a substance. |
Convection |
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The source of heat that produces deep mantle plumes is believed to be located at the __________. |
outer core–mantle boundary (D) |
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Which is Earth's weakest layer? |
Asthenosphere |
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The greatest change in the velocity of P waves occurs at the __________ boundary. |
mantle–outer core |
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Shadow zone |
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. |
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Which of Earth's major divisions is thought to be the source of the magnetic field? |
outer core |
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What layer is composed of the crust plus the uppermost mantle? |
lithosphere |
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This layer averages only about 7 kilometers (5 miles) in thickness. |
oceanic crust |
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This thick shell of rock is composed mostly of silicate minerals that are rich in iron and magnesium. |
Mantle |