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Geology > Ch. 01 > Flashcards

Ch. 01 Flashcards

1
Q

Define Geology

A

Geology focuses on Earth, its rocks, processes shaping it, and surface modeling.

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2
Q

This branch of science focuses on Earth, its rocks, processes shaping it, and surface modeling.

A

Geology

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3
Q

What kind of changes occurs on earth are observable for ex. erosion which affects coastlines and continental heights?

A

Surface Changes

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4
Q

This type of changes on earth involve slow continent movements, volcanic erruptions, and earthquakes.

A

Subsurface Changes

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5
Q

What type of energy transactions influence geological processes?

A

Solar energy, geothermal heat loss, and seismic energy release/earthquake

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6
Q

What impacts engineering at rates comparable to comon practices?

A

Geological effects

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7
Q

What serves as earths history books, preserving events and remains of living organisms?

A

Rocks

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8
Q

What are the tree major rock groups?

A

igneous, sedimentary, and metamorphic

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9
Q

It is composed of minerals, forming a mechanical basis of geological materials in engineering.

A

rocks

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10
Q

How do you differentite rocks from soils?

A

Rock - denotes hard materials
soil - refers to sediments or granular residues

they can be differentiated from their sizes using a sieve.

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11
Q

_______ & _______ contains pores and fissures filled with liquidor gas.

A

rocks and soils

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12
Q

By how much shorter is the earth’s polar radius from its equitorial radius? and why is that?

A

22km, this makes the earth’s shape slightly oblate due to its rotation and the centrifugal force.

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13
Q

Approximately, what percentage of earth is land?

A

29%, almost 35% including continental shelves

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14
Q

What part of the earth cover about two-thirds of the earth’s surface?

A

the Oceans

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15
Q

What is the average land height?

A

0.86 km above sea level

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16
Q

what is the mean ocean floor depth?

A

about 3.8 km

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17
Q

True or False: Extremes in height and depth are limited and small compared to Earth’s radius

A

TRUE

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18
Q

What is composed of oceans, seas, lakes, and rivers, collectively?

A

the hydrosphere

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19
Q

The Earth is surrounded by a gaseous envelope called?

A

the atmosphere

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20
Q

What advanced measurement techniques revealed detailed ocean floor surveys?

A

seismic refraction

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21
Q

What are the continental margin features?

A

continental shelf (gentle slope), shelf break, continental slope, and continental rise.

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22
Q

What plain is reached below 2700 fanthoms (5km) ?

A

The deep abyssal plain

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23
Q

This hosts submarine volcanic islands and drowned peaks related to oceanic ridges.

A

Abyssal plain

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24
Q

It is a submerged extension of land with a gentle slope

A

Continental shelf

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25
Q

It is marked change in slope leading to the continental slope.

A

Shelf break

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26
Q

continental slope transitions to the continental rise with a _______

A

diminishing gradient

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27
Q

Volcanoes rising from the abyssal plain may form ________

A

sea mounts

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28
Q

Volcanoes no longer breaking the earth’s surface are called

A

sea mounts

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29
Q

These are sumbarine chains of mountains rising 2 to 4 km above the ocean floor

A

Oceanic ridges

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30
Q

What defines the base of the lithosphere?

A

at 30km depth, rocks could begin to melt and temperature increases downward at an average of 30 deg per km

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31
Q

What is the earth’s core made of ?

A

a mixture of iron and nickel

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32
Q

What surrounds the earth’s core?

A

Mantle

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33
Q

What is the thickness of the earth’s crust?

A

in continental areas, 30 km
in oceans, 10 km

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34
Q

What do seismic studies use to gain insights into Earth’s interior structure?

a) Magnetic fields
b) Elastic waves from earthquakes
c) Gravity measurements
d) Atmospheric pressure

A

b) Elastic waves from earthquakes

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35
Q

What is the approximate density of Earth’s core as revealed by seismic studies?

A

8

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36
Q

Where are earthquake centers mainly located, according to seismic studies?

A

In two surface belts, one around the Pacific and the other from Europe to Asia

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37
Q

What causes earthquakes?

A

Fractures (faults) relieving stress in crustal rocks

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38
Q

What can serve as precursors to earthquakes?

A

Changes in land shape, water levels, and seismic activity

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39
Q

How do earthquakes vary in intensity?

A

From slight tremors to severe shocks causing various damages

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40
Q

How can the impact of earthquakes be mitigated in affected areas?

A

Through earthquake-resistant structures and designs

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41
Q

What phenomenon can result from rapid changes in ocean floor elevation during sea earthquakes?

A

Tsunamis

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42
Q

Where are earthquake centers primarily concentrated globally?

A

Along two belts: the circum-Pacific belt (75%) and the Alpine area (22%)

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43
Q

What is used to estimate earthquake intensity, and what is the scale’s range?

A

Mercalli Scale; I to XII

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44
Q

What do isoseismal maps mark during an earthquake?

a) Points of equal temperature
b) Points of equal intensity
c) Points of equal air pressure
d) Points of equal humidity

A

b) Points of equal intensity

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45
Q

How is seismic energy release measured during an earthquake?

A

Magnitude (M) on Richter’s logarithmic scale

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46
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47
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47
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48
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49
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49
Q
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50
Q

What does the magnitude (M) of an earthquake correlate with?

A

Seismic energy

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50
Q

What is the approximate threshold for an earthquake to be considered a major disaster in terms of magnitude (M)?

A

M=7

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50
Q

How are the Richter Scale and the Mercalli Scale related?

A

They are not directly comparable, but M=5 roughly corresponds to Grade VI on the Mercalli Scale

50
Q

What type of waves do earthquakes generate that propagate from the focus to the epicenter?

A

Seismic waves

50
Q

What are the primary types of seismic waves?

A

Primary (P) and Secondary (S) waves

51
Q

How do seismographs record vibrations during an earthquake?

A

With a pivoted beam carrying a mass

51
Q

What is the shadow zone in the context of seismic waves?

A

An area where P and S waves do not arrive

51
Q

What does the Mohorovicic discontinuity (Moho) mark in Earth’s interior?

A

Crust-mantle boundary

52
Q

How is crustal structure determined using seismic waves?

A

By observing waves traveling through crustal rocks

53
Q

What is the average thickness of continental crust?

A

30 km

54
Q

what does the Earth’s outer lithosphere rest on?

A

Upper mantle

55
Q

What is indicated by vertical and horizontal lithospheric movements ?

A

Continental drift and plate tectonics

56
Q

What geological concept unifies isostacy and continental drift ?

A

Plate Tectonics

57
Q

What does the term isostacy refer to in the context of Earth’s crust?

A

The balance between continental masses and underlying sub-crustal material

58
Q

How is isostatic balance tested?

A

gravity surveys

59
Q

What is the primary role of the asthenosphere in isostatic adjustment?

A

Facilitating slow upward movements during denudation

60
Q

How did the Earth’s height, particularly in areas like the Himalayas, maintain during isostatic adjustment?

A

denudation involving the removal of significant rock quantities

61
Q

What geological event during the Glacial epoch caused the depression of land areas

A

Thick ice-sheets

62
Q

What is the estimated rate of Earth’s expansion?

A

1 cm per year

63
Q

According to the Earth’s expansion hypothesis, what might explain the inconsistencies in paleomagnetism?

A

Earth’s slow expansion

64
Q

What is the primary driving force behind the mechanism of continental drift?

A

Mantle convection currents

65
Q

What is the state of balance maintained in isostasy called?

A

Level of compensation

66
Q

Define asthenosphere in the context of Earth’s structure

A

Weak layer beneath the lithosphere.

67
Q

What role does the asthenosphere play in isostatic adjustment during denudation?

A

Facilitates slow rise of the surface, lightening it.

68
Q

Who proposed the concept of continental drift, and in which year

A

Alfred Wegener in 1912.

69
Q

Why was Wegener’s continental drift idea initially met with controversy?

A

Lack of supporting evidence.

70
Q

What evidence did Wegener use to support continental drift?

A

Similar coastlines, geological features, and fossil faunas.

71
Q

According to A.L. du Toit, what demonstrated an accurate fit between continents?

A

Fit between Africa and South America at their continental shelves.

72
Q

What does rotational change refer to in the context of continental drift?

A

Changes in the position and orientation of continents.

73
Q

Give an example of a shared feature supporting past adjacency between continents.

A

Similar mountain ranges between North America and Europe.

74
Q

Around how many million years ago did Gondwanaland exist, according to the text?

A

400 million years ago.

75
Q

What evidence suggests a shared glaciation event in Gondwanaland?

A

Glacial deposits in southern Africa, India, Australia, Brazil, and Argentina.

76
Q

Approximately how long ago did Africa and India move northwards and collide with Eurasia?

A

200 million years ago.

77
Q

What is observed between drifting continents?

A

Oceanic ridges.

78
Q

What structures resemble submerged mountain ranges found in all oceans?

A

Oceanic ridges.

79
Q

What extends along the summit of the mid-Atlantic Ridge?

A

Median rift.

80
Q

What process is indicated by radiometric dating of basalts in oceanic ridges?

A

Ocean floor spreading.

81
Q

What is involved in ocean floor spreading?

A

Lateral movement of volcanic material creating new ocean floor.

82
Q

What type of rocks provide independent evidence for ocean floor spreading and continental drift?

A

Basaltic rocks.

83
Q

Which mineral with magnetic properties is found in basaltic rocks?

A

Magnetite.

84
Q

What term is used for retained magnetic properties in rocks, revealing changes in their position over time?

A

Palaeomagnetism or fossil magnetism.

85
Q

What pattern is observed on basaltic rocks on oceanic ridges, such as the North Atlantic Ridge?

A

Striped pattern parallel to the median rift.

86
Q

What does alternate striping of reversed magnetism on basaltic rocks indicate?

A

Periodic reversals of Earth’s magnetic poles.

87
Q

How is the dating of magnetic stripes on the ocean floor accomplished?

A

Radiometric dating.

88
Q

When did the last reversal of Earth’s magnetic field occur?

A

About 700,000 years ago.

89
Q

What does the increasing age of basaltic rocks with distance from the median rift indicate?

A

Duration of ocean floor spreading.

90
Q

What is the estimated present rate of ocean floor spreading?

A

Between 1 cm and 3 cm per year.

91
Q

What distinguishes rocks near the center of oceanic ridges in terms of temperature?

A

They have higher temperatures compared to those on either side.

92
Q

What drives the upward flow of material from the mantle in oceanic ridges?

A

Mantle convection currents.

93
Q

What is the driving force behind the upward flow of material in oceanic ridges?

A

Buoyancy due to lower density in the rising current.

94
Q

How are horizontal displacements accommodated in the mechanism of continental drift?

A

Through displacement on fractures called transcurrent faults.

95
Q

What geological role do extensive fracture systems with horizontal displacements play?

A

They contribute to the Earth’s crust architecture.

96
Q

Which major geological feature is formed where two continental plates converge?

A

Intercontinental fold mountain belts.

97
Q

What does seismic data collected by a worldwide seismic network support?

A

Plate tectonics theory.

98
Q

How is new sea-floor formed?

A

Oceanic Ridges

99
Q

How is the destruction of oceanic crust balanced in the Earth’s crust?

A

Through subduction.

100
Q

What emerged as a geological idea in the mid-1960s, considering the lithosphere as a mosaic of plates?

A

Plate tectonics.

101
Q

What are the three types of plate movements mentioned in the text?

A

Sliding past each other, moving away from each other, and one sliding underneath the other.

102
Q

Name a type of plate capped by continental crust, according to the text.

A

Continental Plates.

103
Q

What concept suggests that the Earth is slowly expanding, increasing its surface area?

A

Earth’s Expansion Hypothesis.

104
Q

What evidence does the Earth’s Expansion Hypothesis use to support its claims?

A

Palaeogeographical maps, astronomical evidence, and paleomagnetism inconsistencies.

105
Q

What is the estimated rate of the Earth’s expansion according to the hypothesis?

A

0.24 mm per year, totaling about 20% in 4500 million years.

106
Q

When did Earth and other Solar System bodies form?

A

Around 4600 million years ago.

107
Q

What process led to the formation of the primitive Sun at the center of the Solar System?

A

Gradual contraction from a rotating, flattened cloud of gas and dust.

108
Q

How did planets, including Earth, form?

A

From local condensations in the rotating cloud.

109
Q

What initially characterized the primitive Earth before it gradually heated?

A

It was cold.

110
Q

What factors contributed to the heating of the primitive Earth?

A

Compression and decay of radioactive materials.

111
Q

What geological components formed due to the melting of the primitive Earth?

A

Core, mantle, and outer crust.

112
Q

Approximately, when do the oldest discovered rocks on Earth date back to?

A

About 3900 million years.

113
Q

When did the primitive crust likely form, and what type of crust was it?

A

Around 4400 to 4500 million years ago; likely basaltic.

114
Q

What contributed to continent formation during the primitive crust’s evolution?

A

Separation of lighter (granitic) fluids after cracking and re-melting.

115
Q

How did the early oceans on Earth form?

A

As the Earth’s surface cooled, water collected.

116
Q

When is it suggested that the modern atmosphere likely formed?

A

Within the last 1000 million years.

117
Q

What scientific method is used for modern estimates of rock ages?

A

Radiometric methods.

118
Q

Who discovered radioactivity, enabling age calculations based on element transformations?

A

Pierre and Marie Curie.

119
Q

Which radioactive transformation is useful for dating igneous rocks?

A

Potassium into argon.

120
Q

Which radioactive transformation is useful for dating metamorphic rocks?

A

Rubidium into strontium.

121
Q

What method is employed for dating materials like wood and plant remains for smaller ages?

A

Carbon-14 dating.

122
Q

How are rocks classified into geological groups?

A

Based on their age.

123
Q

Why is the geological history of rocks crucial for engineering purposes?

A

Understanding the mechanical character of rocks and soils.

124
Q

What fraction of geological time is particularly important in engineering?

A

The last one-eighth.

125
Q

What era represents approximately seven-eighths of geological history?

A

Precambrian Era.

126
Q

How is the Precambrian Era described in terms of our knowledge?

A

Poorly known but essential for understanding Earth’s geological evolution.

Geology (6 decks)

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