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PHY S 100 > Units 26-27 > Flashcards

Units 26-27 Flashcards

1
Q

What are the five categories of evidence that teach us about earth’s interior?

A
  1. Direct observation of rocks from interior
  2. Relationships to rocks or meteorites from space
  3. Inferences from Earth’s density
  4. Evidence from seismic (earthquake) waves
  5. Requirements for producing Earth’s magnetic field
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2
Q

What brings deep rocks to the surface that can’t be reached by drilling or other ways?

A

Volcano blasts and ascending magmas.

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3
Q

Crust

A

The uppermost compositional layer of Earth.

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4
Q

Characteristics of the crust:

A

Very thin
Composed of two parts: Granitic continental crust and basaltic oceanic crust

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5
Q

True or False: Rocks brought to the surface by volcanoes are denser than the basalts on the ocean floor.

A

True

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6
Q

Mantle

A

The middle compositional layer of earth.

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7
Q

Characteristics of Mantle:

A

Thick layer
Made of peridotite in the upper part
and higher density rocks of peridotite composition in the lower part.

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8
Q

Peridotite

A

Rock made up of mostly silicon, oxygen, iron, and magnesium.

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9
Q

True or False: Peridotite is denser than the basalt and granite of the earth’s crust

A

True

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10
Q

Meteorites

A

A rock from space that HITS earth’s surface

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11
Q

Stony chondrites

A

Meteorites thought to be composed of unprocessed material from the original solar nebula

The same materials that our planet and solar system were originally made.

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12
Q

What percentage of meteorites are stony chondrites?

A

86%

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13
Q

Stony achondrites

A

Meteorites thought to represent material from small planetary bodies that had differentiated into layers and then were broken up.

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14
Q

What percentage of meteorites are stony achondrites?

A

8%

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15
Q

Iron meteorites

A

Meteorites thought to represent the type of material found in Earth’s core

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16
Q

What percentage of meteorites are iron?

A

6%

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17
Q

Core

A

The deepest or central compositional layer of Earth. It is composed mostly of iron

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18
Q

What is the equation for Earth’s mass?

A

M = gR^2 / G

M = mass of earth
g = acceleration of gravity
R = radius of earth

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19
Q

Why do we care what Earth’s density is?

A

Because that tells us about the rocks that compose it.

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20
Q

Why do we care about Earth’s mass?

A

Because having the mass lets us calculate density

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21
Q

True or False: Earth’s surface is elastic

A

True
It rebounds back into shape when pressure is released

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22
Q

Elastic rebound

A

The point at which stress in Earth’s lithosphere is strained to a point where it can bend no further. When this happens, the lithosphere ruptures and rebounds somewhat like a rubber band that has just been pulled apart.

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23
Q

Fault

A

A break in earth’s lithosphere where rocks on one side of the break have slipped past the rocks on the other side

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24
Q

What causes faults exclusively?

A

Earthquakes

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25
Q

What characteristic of earth are faults a result of (not earthquakes)?

A

Elastic rebound

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26
Q

Tectonic plates

A

The brittle, rigid but thin outer part of Earth is divided into sections called tectonic plates

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27
Q

Seismic waves

A

Waves produced by earthquakes (caused by tectonic plates rubbing against each other, smashing into each other, and slipping.

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28
Q

Seismos translation?

A

Earthquake in Greek

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29
Q

True or False: Earthquakes simultaneously produce compression, shear, and surface waves.

A

True

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30
Q

Which type of waves travel fastest, compression, shear, or surface?

A

Compression

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31
Q

P waves

A

Primary waves.
These are compression waves produced by an earthquake. They travel the fastest so they reach the measuring detectors first (primary).

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32
Q

S waves

A

Secondary waves.
Shear waves. They are second to arrive at seismic detectors

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33
Q

What is the slowest type of wave?

A

Surface

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34
Q

Focus

A

Point of origin in an earthquake.

The place inside the earth where an earthquake originates

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35
Q

Epicenter

A

The point on Earth’s SURFACE directly above the focus of an earthquake

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36
Q

True or False: The speeds of P and S waves change depending on the type of rocks/materials they are passing through.

A

True

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37
Q

True or False: The stiffer the rocks, the slower the wave speed.

A

FALSE
The faster the wave speed

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38
Q

Why do wave speeds and directions REFRACT inside the earth’s surface?

A

Because of the properties and elasticity of the rocks they are travelling through, which vary by density.

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39
Q

Seismographs

A

The detectors in the grid of earthquake recording stations.

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40
Q

Seismometers

A

Device that measures ground motion

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41
Q

Seismic discontinuity

A

A place where the velocities of seismic waves change abruptly.

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42
Q

Moho

A

Short for Mohorovicic discontinuity. It is the location of the boundary between densities. At the base of the earth’s crust.

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43
Q

Shadow zone

A

A region of earth where seismic waves cannot be detected by seismometers.

Look at 26.7 figure. Easy.

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44
Q

Outer core

A

The upper part of the core that is made of liquid iron

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45
Q

How did we figure out that the outer core (or any part of the earth’s interior) was liquid?

A

Because of the shadow zones. Shear waves can only travel through a solid.

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46
Q

Inner core

A

The lower part of the core that is made of solid iron

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47
Q

What happens to the density as you move in through the core of the earth?

A

It increases

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48
Q

Curie temperature

A

The temp at which a material loses its magnetism (not a permanent magnet anymore)

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49
Q

True or False: Earth’s magnetic field is produced by a giant, iron core that is magnetized.

A

FALSE
The core is not magnetized (too hot, curie temperature explanation)

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50
Q

What causes earth’s magnetic fields?

A

Electrical currents in the earth

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51
Q

What causes the electrical currents in the earth?

A

The difference in temperature between the inner and outer core (solid and liquid) creates convection that move iron atoms in great cylindrical cells that rotate equatorially (earth’s rotation).

Relies on the Sun’s magnetic field.

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52
Q

True or False: There are many types of rock in the earth’s crust, including igneous, sedimentary, and metamorphic.

A

True
It averages granite

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53
Q

Silicates

A

Minerals that contain silicon and oxygen bonded together

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54
Q

True or False: The oceanic crust is virtually all basalt

A

True

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55
Q

Which is more dense, the oceanic or continental crust?

A

Oceanic

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56
Q

Dense oxides

A

Minerals that form deep in earth’s mantle due to the enormous pressures

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57
Q

What is another way to describe “mechanical layers”?

A

The physical behaviors of the rocks in the compositional layers of the crust, mantle, and core

58
Q

What does mechanical behavior refer to?

A

How rocks deform when forces are applied to them.

59
Q

Plastic

A

Non-rigid, deformable, capable of flowing in response to force or pressure.

Basically silly putty

60
Q

Lithosphere

A

Earth’s outermost rigid, brittle, skin-like layer. Solid rock.
It consists of the crust and the outermost part of the mantle that is too cool to be molten.

61
Q

True or False: The lithosphere is the only layer in which earthquakes can occur

A

True

62
Q

Which mechanical layer is the Moho found in?

A

Lithosphere

63
Q

True or False: Tectonic plates float

A

True

64
Q

Asthenosphere

A

A soft, plastic, partially molten mechanical layer right below the lithosphere.
This is the layer that tectonic plates float on.

65
Q

low velocity zone

A

A region of the upper mantle (asthenosphere) where seismic waves travel slower than expected.

66
Q

What is the low velocity zone made of?

A

It is the boundary between solid peridotite and partially molten peridotite.

67
Q

Melting point line

A

A line on a plot of temperature AND pressure showing where a substance transforms from a solid to liquid.

68
Q

True or False: Melting points are influenced by temp AND pressure

A

True

69
Q

Why does peridotite only partially melt?

A

Because it is made of many minerals with various melting temps

70
Q

Mesosphere

A

The mechanical layer between the asthenosphere and the outer core

71
Q

Is the mesosphere solid or liquid?

A

SOLID, but plastic, and able to flow.
It’s not the molten lava that everybody says it is.

72
Q

How fast do the plastics in the mesosphere flow?

A

a few centimeters per year.

73
Q

What causes flow in the mantle?

A

Pressure and temperature changes, density differences

74
Q

True or False: The inner core is continually growing because iron is solidifying onto it.

A

True
They think

75
Q

What keeps the center of the earth warm?

A

The enormous amount of heat released from the growing inner core

76
Q

What is the AVERAGE density of earth?

A

5.5 g/cm^3

77
Q

Why can P and S waves help us figure out where earthquakes start?

A

Because they travel at different speeds and reach different seismometers at different times.

78
Q

What does a seismometer produce?

A

Seismographs

79
Q

True or False: We have machines that can get us past the Earth’s crust.

A

FALSE

80
Q

What is easier to understand if we assume that the earth is split up into abrupt layers?

A

Shadow zones (changes of density that create wave speed changes)

81
Q

True or False: P waves are refracted as they encounter an abrupt change of medium

A

True

82
Q

True or False: P waves that travel through the solid core reach the other side of the earth faster than those that did not.

A

True
Solids = faster waves

83
Q

What is a “mechanical layer”?

A

The composition of the layers are the same, but the behaviors of the layers change due to temperature and pressure differences.

84
Q

Why do we assume the core is made of iron and nickel?

A

Because meteorites are found that way, and if we ASSUME it’s iron and use that information in our calculations, Earth’s overall density seems to be correct.

85
Q

Pangaea

A

The name of the supercontinent that broke up about 200 million years ago.

86
Q

Who came up with “pangaea”?

A

Alfred Wegener

87
Q

What does Pangaea mean in Greek?

A

“all earth”

88
Q

Continental shelves

A

The ACTUAL edges of continents (underwater)

89
Q

When did the theory of tectonics and pangaea become widely accepted?

A

1970’s
dang

90
Q

Shield

A

The oldest parts of the continents. They represent the roots of very ancient mountains, long since eroded away.

91
Q

Stable platform (covered shield)

A

An area of the continent where the old rocks of the shield have been covered by relatively flat-lying sedimentary rocks.

92
Q

What is another name for a stable platform?

A

Covered shield

93
Q

Mountain belt

A

Regions of the continents where rocks have been highly deformed by enormous forces. Usually along the edges of continents.

94
Q

Structural trends

A

The orientations of major geologic features such as mountain belts, continental shields, stable platforms, and areas of folded or deformed rocks

95
Q

Paleontologists

A

They study ancient life preserved as fossils in rocks

96
Q

Glossopteris FLora

A

An extinct group of plants that lived 250 million years ago.
These fossils were found all over the world. Seeds could not have been spread across thousands of kilometers of open ocean through natural processes. Contributed to the idea of Pangaea

97
Q

Mesosaurus

A

Water reptile 300 - 250 million years ago.
Again, found across oceans in fresh water, could not have happened (crossed the ocean) if ancient days were separated by oceans.

98
Q

What evidence do glaciers present for Pangaea?

A

There are glacial remains in areas that are warm, and not in areas that are not cold. This helps us understand that tectonic plates moved those regions out of hot and into cold (vice versa).

99
Q

Paleoclimatology

A

The study of ancient climates

100
Q

What evidence did the mid Atlantic ridge provide when it was discovered in the 1950’s-60’s?

A

It aligned almost perfectly with the shelf margins on either side of it, showing that the seafloor MOVED, and was the mechanism that moved the continents.

101
Q

Where are the oldest ocean rocks found, closer or farther away from the continents in their present positions?

A

Farther away

102
Q

True or False: The youngest rocks on the ocean floor are found next to the mid-ocean ridges

A

True

103
Q

Seafloor spreading

A

Theory that the ocean floor GROWS on either side as the mid ocean ridge moves apart.
The rift created in this process is filled in with BASALT as magma squeezes up into the fractures created by rifting.

104
Q

What causes the continents to move?

A

Seafloor spreading, pushing them apart

105
Q

True or False: Earth reverses its polarity (magnetic field) every half million years

A

True

106
Q

Where are earthquakes happening (not lithosphere, surface features)

A

Along the ocean trenches and ridges

107
Q

What is happening to the lithosphere at ridges?

A

The brittle lithosphere is being pulled apart

108
Q

What is happening to the lithosphere at the trenches?

A

It’s sinking back into the asthenosphere

109
Q

Ridge push

A

Helps move earth’s plates. The ridge is high and has gravitational potential energy that is converted into kinetic energy as the plate moves.

This is how tectonics “flow” like liquids.

110
Q

What forces move tectonic plates?

A

Ridge push
Slab pull

111
Q

Slab pull

A

As an oceanic plate becomes old, cold, and dense, it sinks back into the mantle, pulling the rest of the plate along with it (helped by ridge push which is pushing up the other end).

112
Q

Divergent plate boundaries

A

Boundaries where two plates are splitting apart from each other

113
Q

Convergent plate boundaries

A

Boundaries where two plates are colliding with each other

114
Q

Transform boundaries

A

Boundaries where two plates are sliding past each other.

115
Q

True or False: Earthquakes on oceanic ridges produce tsunamis

A

False
They’re milder than collisions

116
Q

True or False: Continental lithosphere is colder than oceanic lithosphere

A

True
Because it’s older

117
Q

Why does some lithosphere have to be destroyed?

A

Because earth isn’t growing in size, and lithosphere is being created elsewhere. To “make room” it has to lose some.

118
Q

What is common at convergent plate boundaries?

A

Spectacular mountains, huge earthquakes, and explosive volcanoes

119
Q

What are the three subtypes of convergent boundaries?

A
  1. ocean ocean
  2. ocean continent
  3. continent continent
120
Q

Subduction

A

Occurs with collisions between two ocean plates.
In a collision of two ocean plates, one will dive under the other and sink into the asthenosphere.

121
Q

Which plate sinks in subduction?

A

older and colder (therefore DENSER)

122
Q

True or False: Subductions create massive earthquakes and tsunamis

A

True

123
Q

Volcanic island arch

A

A chain of volcanoes, shaped like an arc, that form at some convergent plate boundaries

124
Q

True or False: When an oceanic plate collides with a continental plate, it is always the oceanic plate that subducts.

A

True

125
Q

What is often created by ocean-continent collisions?

A

Volcanoes and mountain belts

126
Q

True or False: Continents that collide into each other crash like two cars in a head-on collision. Neither sink.

A

True

127
Q

What happens to separate continents that crash into each other?

A

They become welded together, creating the highest mountain ranges on earth

128
Q

What is one striking difference between continent to continent collisions vs. other collision types?

A

No volcanoes (because nothing is sinking into the mantle)

129
Q

Mantle plume

A

A buoyant mass of hot rock rising through Earth’s mantle. As it nears the surface of Earth, some of the plume melts and erupts at the surface forming a hot spot.

130
Q

Hot spot

A

Many volcanoes that result from the lithosphere moving over a mantle plume.
Hawaii is example.

131
Q

Hot spot trail

A

The trail of volcanoes as the lithosphere passes over the hot spot.

132
Q

Linear island chains

A

A chain of volcanic islands created when an ocean plate moves over a hot spot.

133
Q

Why do hot spot volcanoes become extinct?

A

Because the land mass has moved past the mantle plume so it’s no longer being fed by magma.

134
Q

True or False: The same forces that tore Pangaea apart are the same forces that originally assembled it.

A

True

135
Q

Continental accretion

A

The process by which continents grow. When continents collide with other land masses, new material may be added and the continent grows.

136
Q

Summarize paleomagnetic evidence of Pangaea

A

Magma has magnetite that flows in the direction of the magnetic field. When the magma cools, it freezes in place. We can look at the directions that the magnetite was flowing to see where it came from, and where those land masses fit with OTHER magnetite flows.

137
Q

How quickly do oceanic plates diverge?

A

3-10 cm / year

138
Q

True or False: At a continental divergence, an ocean can form if the rift continues

A

True

139
Q

True or False: All continental divergences cause rifts that continue indefinitely

A

False.
They can stop

140
Q
A

PHY S 100 (18 decks)

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