GEOLOY EXAM3

8/2/2019 GEOLOY EXAM3

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EXAM 3 Study Guide

The following is a list of key terms and concepts that I expect you to know for exam 3. For each term youshould know how it is defined, why is it important, and example(s) used in class.

Earthquakes

Elastic Rebound Theory

The 1906 Earthquake (fig. 11.4) led to the development of the Elastic Rebound Theory(fig. 11.5)

Focus vs. Epicenter of an earthquake

Seismograph vs. Seismogram

focusis the point on the fault plane where the slip (movement) was initiated. (fig. 11.2)

epicenteris the point on the ground directly above the point where the slip (movement) firstoccurred. (fig. 11.2)


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Ground shaking caused by earthquakes is measured by seismograph, instruments whichcan record both vertical and horizontal ground motion

The record of the shaking is a seismogram. These can record the arrival time, duration,amplitude and period of both body and surface waves (fig. 11.10).

Body Waves can travel through the body of the earth. The two types:

Types of Seismic Waves generated in an earthquake, including definitions and characteristics (e.g.relative speed, amplitude, and medium through which they may be transmitted).

P-wavesare compressional waves. They exert a push-pull motion on the rocks parallel to thedirection of wave propagation. They are also referred to as "Primary-waves".S-wavesare shear waves.They exert an up and down motion on the rocks perpendicular to the

direction of wave propagation. They are also referred to as "Secondary-waves".Surface Wavesform when the energy of body waves intersects the surface of the earth. That energy

P-Waves S-Waves Surface Waves

eefastest intermediate slowest

mplide

lowest intermediate highest

rioshortest intermediate longest

ediuSolidLiquidGas

SolidSolid

Liquid


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then is trapped at the surface, where it then travels as waves along the ground.

Time Lag Between S and P waves increases with Distance from Epicenter

What is a Time-Distance graph and how can it be used to locate the epicenter of an earthquake?

The time-Distance graph: plots the predicted arrival time of S- and P-waves as a functionof distance.By determining the distance from the epicenter using time lag data, the intersection ofcircles from the various seismograph locations will indicate the source (epicenter) of thequake.

What is the S-P time lag and why is it important?

it can be used to determine distance from the epicenter using only data obtained for aseismogram record

What type and depth earthquakes are usually associated with different types of plate boundaries?

Name Depth Boundary

shallow < 70km oceanic ridge

intermediate 70km - 300km


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XSome well-built structures destroyed. Most masonry and framestructures destroyed. Ground badly cracked

XI Few masonry structures remain standing; bridges destroyed

XII Damage total; waves seen on ground; objects thrown into air

Magnitudemeasures the energy released during an EarthquakeMr =log 10(Amplitude [measured on bedrock 100 km from epicenter])

This can be determined from a seismogram as amplitude and distance can bedetermined from a single seismogram.

In theory, it is an open ended scale, however the largest quake ever recorded had a M =8.9. Why should there be an upper limit in nature?

How does amplitude of shaking and energy vary with magnitude ?

This is a Logarithmic Scale, i.e.

5. Increase 1 unit = 10 times greater shakingIncrease 1 unit ~ 32 times greater energy

What are the hazards associated with earthquakes? Examples?6. 1. Building failure caused by

0 Fault Rupture1 Ground shaking

2 Liquefaction of sediment3 Landslides

7. 2.Tsunamis8. 3. Dam Failure

9. 4. Fires

Know the significance of the following historical earthquakes:

1811-1812 New Madrid Earthquakes


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10. Hit by three huge earthquakes.

11. Changed the course of the Mississipi

12. X-XI on Mercalli scale

13. The most widely felt earthquake in US historyNot felt west of the Mississipi because no one was there to record it.

1906 San Francisco Earthquake

14. M ~ 8.1-8.2

15. Lives Lost: 700

16. Damage: ~$400 million (most due to fire). Greatest damage on "made-land".

17. Transform Plate BoundarySome effects:

1964 Good Friday Alaska Earthquake

18. M = 8.3-8.4

19. Lives Lost: 131

20. Damage: ~$310 million

21. Notable for large tsunami and pattern of re-building

22. Some effects (fig. 11.17)

0 Landslide at Turnagin Heights (fig. 11.22)

Prince William Sound, 1964

1971 San Fernando Earthquake

23. M = 6.5

24. Lives Lost: 65

25. Damage: ~ $ 550Million

26. Lesson learned:

0 existing building codes for highways not adequate;1 dam almost failed

27. Transform Plate BoundarySome effects

1985 Mexico City Earthquake


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28. M = 8.1

29. Lives Lost: 9500

30. Damage: ~$4 billion

31. Notable for damage occurring >350 km from epicenter due to differential ground amplification and

building characteristics (fig. 11.18)

32. Convergent Plate BoundarySome effects

1988 Armenian Earthquake

33. M = 6.9

34. Lives Lost: ~25,000 (100,000?)

35. Damage: $14.2 billion

36. Lessons: poor construction techniques resulted in high losses for moderate earthquake.Transform (?) Plate Boundary

1989 Loma Prieta (World Series) earthquake

37. M = 7.1

38. Lives Lost: 62

39. Damage: $6 Billion

40. Lessons: Bridges and overpasses still not safe. Role of local geology.

41. Transform Plate Boundary

42. Some effects (fig. 11.14)

0 Collapsed Oakland Freeway

1 Role of Geology in Freeway Collapse (fig. 11C)

2 California Speed Bump

3 House collapse due to landslideFAULT!

1994 Northridge Earthquake43. M = 6.7

44. Lives Lost: 61

45. Damage: $15-25 Billion

46. Notable for the amount of damage in a moderate EQ and the implication of a "blind thrust"

47. Transform Plate Boundary


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48. Mercalli Intensity Map of the 1994 Northridge EarthquakeSome effects: Highway Failure in 1994 Earthquake

2004 Boxing Day Earthquake

2005 Pakistan Earthquake 2010 Haiti Earthquake 2011 Japan Earthquake

The Interior of the Earth

Know the Compositional and Mechanical layers of the earth, e.g.: crust, mantle, inner core, outer core,lithosphere, asthenosphere (where are they and what are their properties?)Compositional Layers

49. 1. Crust0 Oceanic (~ 5 km)

1 Continental (~ 40 km)

50. 2. Mantle (~2900 km)

51. 3. Core (~3500 km)

Mechanical layers

1. 1. Lithosphere

2. 2. Asthenosphere

3. 3. Mesosphere

4. 4. Outer Core5. Inner Core

Refraction : what is it, why does it occur, and what does it tell you?

Seismic Refractionthe bending of wave rays caused by a change in velocity

S- and P-Wave Shadow Zones (what are they, how are they formed, and what doe they tell us?)

Q. What is the S-wave shadow zone and where does it occur?

A. Something opaque to shear waves, which prevents S-waves from reaching from thenorth pole to an area 15% south of the equator.

Q. What is forming the S-wave Shadow Zone?


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A. Liquid outer core.

The S-wave shadow zone

Q. We know where the core/mantle boundary is and that it is at least the outer part

of the core is liquid. What else do we know about the core?

A. There is a higher-density inner core.

Q. What is the P-wave Shadow Zone? (fig. 12.8)

A. A donut-shaped zone on the opposite side of the earth from an earthquake where noP-waves show up. The absence is caused by the P-waves being refracted through theearth's core.

What does a typical seismograph looks like:

0-105 o from the epicenter P- and S-waves105o 140 o from the epicenter flat line140o 180 o from the epicenter P-waves only

How does the velocity of P- and S-waves vary with depth?

What is the Moho and how was it detected?

The moho is a discontiuity between the continental and oceanic crust and the uppermantle.

The moho was discovered because P-waves arrived earlier down range than predicted.The P-wave hits the moho, speed up, and exit down range faster than if there was nomoho

Isostacy:

Why do mountains have roots


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The less dense crust "floats" on the less buoyant, denser mantle.

Why is it so hard to erode a mountain range flat?

After eroding, the root floats up.

What are the sources of geothermal heat?

52. 1.Original heat (impact and gravity)2.Subsequent radioactive decay

What are the mechanisms of heat transfer in the solid earth?

53. 1.Conduction54. 2. Convection

3.(Radiation?)

Surface Water

Relative size of global H 2O reservoirs

55. Ocean 95.96%56. Ice 2.97%

57. Ground Water 1.05%58. Lakes 0.01%59. Soil Moisture 0.008%60. Atmosphere 0.001%

61. Rivers 0.0001%Biosphere 0.00004%

Processes by which H 2O move from one reservoir to another.

Hydrologic Cycle

How do different variables affect infiltration & runoff (examples)?

Runoff = rainfall - infiltration

How does runoff vary with:


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62. Surface Slope (gentle vs steep)63. Soil Type (sandy vs clayey)64. Rainfall Intensity (gentle vs high)65. Soil Saturation (low vs high)

66. Vegetation (high % vs low %)Land Use (natural vs build up, e.g. paved)

What determines the volume of floodwaters at a specific location?

67. 1.Amount of Rainfall (inches or cm.)68. 2.Amount of Infiltration (inches or cm.)

3.Area of Drainage Basin (mi 2 or km 2)

Drainage Basin (watershed) & Drainage Divide

Drainage Basinthe area drained by a river at a particular point. Also referred to as the "Watershed".Drainage Divideseparates adjacent drainage basins

What is discharge and how is it measured?

Discharge (Q) is measured using a simplified form of the Continuity Equation:

69. Q = VA70. Q = discharge (L 3 /s)

71. V = average flow velocity (L/s)A = cross sectional area of water (L 2)

What is stage and how is it measured?

the elevation of the floodwaters.Its measured by a hydrograph

What is a Hydrograph?

plots discharge (or stage) at a gaging station over time.


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Floodplain Zonation Map

Maps floodplains at different stages.

How is flood frequency measured?

Flood Frequency is measured by:

72. 1.Recurrence Interval2. Exceedence Probability

What is Annual Recurrence Interval and Exceedence Probability ? How are they calculated?

The RI of an event of a particular magnitude can be determined using the followingequation:

RI = (N + 1) m

Where N = number of years of record and m = rank of the event

Exceedence Probability is the probability (P) of an event a particular magnitude beingequaled or exceeded in any given year. It is the reciprocal of RI.

P = 1 RI

Therefore, a 100 year flood has a 1 in 100 (i.e. 1%) chance of being equaled orexceeded in any given year.

A better term for a 100-year flood is: 1% flood.

What are the 50 and 100 year floods and how are they determined?

The Hundred Year Floodplain is the area flooded by the hundred year flood.

The Hundred Year Flood is a flood with an annual recurrence interval of 100 years.

What are the 2% and 1% floods and how are they determined?

How and why do hydrographs differ before and after urbanization ?


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When an area changes from rural to urban, the lag time between rainfall and flood peakis shortened and the flood peak is higher.

How can you increase velocity in a channel? Why would you want to do that?

73. 1.Decrease Resistance to Flow74. 2.Increase Channel Efficiency75. 3.Increase Slope

This is "improving the channel" or "channelizing"

What are the variables in Mannings Equation and how do they relate to flood control?

V = ( 1.5 R 2/3S 1/2 ) n

76. V = Average Water Velocity77. R = Hydraulic Radius ( a measure of the efficiency of the channel cross section)

78. S = Slope of the Energy Gradient (approximated by the slope of the channel)79. n = Manning's Roughness Coefficient (a measure of the resistance to flow)

Examples of different roughness coefficients: Increase roughness, slow velocity down.Decrease roughness, increse velocity.

What is Sinuosity ?

Sinuosityof a stream is a measure of how much it is meandering. It is defined as the channel

distance / linear (or valley) distance, i.e. distance as the fish swims / distanceas the crow flies

How and why has sinuosity changed in Brays Bayou between 1946 and the present?

It was greatly straightened to make water flow go faster and reduce flooding.

What is the effect of channelization on downstream flooding? Alternatives?

Increases downstream flooding and erosion.

Lateral migration , point bars , cut banks , and meander scrolls


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LATERAL MIGRATION: The process in which a meandering river moves by eroding itscutbanks, and building up its point bars.point barinside of a curve in a river, that grows with sediments.cutbankthe outside of a curve in a river, that erodes in a flood.meander scrollsthe layered deposits on point bars that grow while a river migrates laterally.

Meander cutoffs and oxbow lakes

Ultimately, a migrating river's bends will curve so drastically that its cutbanks will merge,leaving behind an abadonded stretch of river called an oxbow lake.

Avulsion

The process in which a river break through the base of a loop, cutting off the meander,and leaves the curve behind as an oxbow lake.

Natural levees

During a flood, the river slows down and deposits heavier sediments on the shoulders ofthe banks of the river, creating higher shoulders and creating a natural levee.

What is significant/lessons learned about the following case studies:

-Red River of Texas/Oklahoma

-1994 Pipeline Rupture along the San Jacinto River east of Houston

-Oyster Creek east of the Brazos River

-The Atchafalaya River north and west of Baton Rouge, LA

-The town of Simonton on the Brazos River west of Houston


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The Coastal Zone

What happened on Sept 8, 1900 ? And in 1915 ?

Sept 9, 1900: Galveston Hurricane, the greatest loss of life in a natural disaster.

What is the Sediment Budget and why is it important?

The rate at which sediment (mainly sand) is removed (wave energy) verses the rate atwhich it is being re-supplied to the beach (sediment supply). The ratio of wave energy tosediment supply.Its important because it determines whether a beach is eroding or stable

What is the difference between a deep-water and shallow-water wave ?

80. Deep Water Wave (D > L/2)

Shallow Water Wave (D < L/2)What is wave base and why is it important?

The wave base is 1/2 the wave length, beneath which wave motion cannot be detected.

What happens in the zone of wave buildup ?

Because the water depth decreases, the wave length decreases, height increases, andwave refraction can occur.

How does the surf zone differ from the zone of wave buildup?

In the surf zone breakers form.

How does wave refraction occur in the near shore zone and why is it important? How does it affectheadlands and bays?

The bending of waves as they change velocity. So as waves change velocity as theyapproach shore, they change direction. Only shallow water waves can change theirvelocity.

What is longshore drift ? How and why does it occur? Why is it important?

Longshore Drift


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The transport of sediment (e.g. sand) parallel to the shoreline, mainly in the surf andswash zone.It is driven by longshore currents set up by waves coming into the shoreline at an angleless than 90 degrees.

What are the main sources of sediment to the beach?

81. 1.Rivers

82. 2.Erosion83. 3.Longshore Drift

4. Others?

What happened near Freeport when the course of the Brazos River was changed?

A huge delta formed, and Freeport was deprived of river sediments resulting in beacherosion.

For each of the following, know what they are their purpose , and the consequences of using them:

GroinsImpermeable structures perpendicular to the shoreline. Purpose: to trap sediment,thereby preventing or reducing beach erosion Problems? Beaches downbeach from thegroin erodes faster.

JettiesImpermeable structures perpendicular to the shoreline, on either side of an inlet.Purpose: to reduce sedimentation in the inlet, thereby improving navigation. Problems?Causes pile-up and increased downdrift erosion.seawalls and revetmentsImpermeable structures parallel to the shoreline, usually on the landward side of thebeach. Purpose: to prevent erosion of the land adjacent to the beach .Breakwater

Impermeable structures parallel to and offshore from the shoreline. Purpose: toprotect a beach or boat anchorage from incoming waves

Important Case Studies:

- Freeport, TX


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- Ocean City, NJ- Galveston, TX

Are Texas beaches eroding , and if not, what is happening? Are there any exceptions to this

generalization?84. 1. Our Beaches are moving

2. Our Beachfront Land is Eroding (to create beach)

What defines the public easement for beaches in Texas.

What is beach nourishment and what are its consequences?

The artificial addition of sand to the beach to reduce the rate of beach erosion.The beach will erode anyway, and will have to be nourished again.

What will be the effect of the large Geo- tubes placed behind the beach just down-drift of theGalveston seawall?

The Geo-tubes saves the land, but does not stop erosion, so beach nourishment willhave to happen (expensive).

Compare the impacts of Hurricane Ike on Bolivar Peninsula and Galveston Island. Why was there such a

big difference?

Groundwater

Main use of groundwater in the U.S. and in Texas is:

for irrigation.85. 80% - Agricultural (mainly irrigation)(projected to be 59% by 2050)

15% - Municipal5% - Industrial

How and why is the amount of groundwater expected to change in Texas over the next 40 years?


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Water Table is:

The top of the saturated zone of groundwaterThe level to which water will rise in a hole

The level to which water will rise in an unconfined aquifer

Saturated Zone

that area where the grains are saturated with water. All the pore spaces are filled withwater.

Unsaturated zone

the area above the saturated zone whre the grains are not saturated with water.

Cone of Depression

Know how and why the water table (and pressure surface) can change with time.

Darcys Law

is used to determine the velocity of ground waterVg = ( KS ) p;

86. Vg = velocity of groundwater87. K ~ permiability88. S = Slope (hydraulic gradient)

p = porosity

Porosity

The percent void space in a rock or sediment. It is a measure of the potential volume ofwater that can be stored in a rock. The greater the porosity, the more fluid that can be

stored in a rock.

Permeability

The ability of a material to transmit a fluid. It is a measure of how fast the fluid can travelthrough the rock or sediment.


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Unconfined and Confined Aquifer

Aquitard

Relative porosity and permeability values for different types of sediments and sedimentary rocks (c.f.table 12.2)

Rock Type Porosity Permeability

ravel V. High V. high

Well-sorted sand V. High High

oorly sorted sand Mod - Low Mod to Low

Well-sortedndstone

Mod - Low Low

ractured shale Low Very Low

imestone Low - High Low - High

Recharge Zone

Pressure Surfacethe level to which water will rise in wells in confined aquifers.

Flowing and non-flowing artesian wells

Know the geologic origin and significance of the following aquifers in Texas:


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-- Gulf Coast Aquifer

-- Edwards Aquifer

-- Ogallalla Aquifer

Which is more likely to be contaminated by surface pollution, an unconfined or confined aquifer? Why?unconfined, because it is exposed to the surface

How can your neighbor pumping his well cause your well to be contaminated?

Resources

Reserves verses Resources

Resourcea naturally occurring material that is of potential economic use.Reservea resource that can be economically and legally used today.

Can the size of reserves and resources change, and if so, how?

What are the sources (and relative magnitudes) of energy on the earth?

89. Solar (99.97%) Radiation : 120,000 units/yr90. Geothermal Energy : 30 units/yr

Gravitational Energy : 3 units/yr

What are Fossil Fuels and how do they form?

Those energy resources that have formed as the result of the burial and subsequenttransformation of organic material.

Photosynthesis verses oxidation

The U.S. produces more __ coal than any other energy source.


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The U.S. consumes more petroleum ___ than any other energy source.

How has the amount of energy produced and consumed in the U.S. changes over the past 50 years, and

so what?What are the sources (and relative amounts) of energy used to produce electricity in the US today?

What does it take to produce coal ?

91. 1.Production of large amounts of biomass

92. 2.Preservation in an oxygen-poor environment3.Burial and compaction

What does it take to produce oil and gas ?

93. 1. Production of large amounts of biomass

94. 2. Preservation in an oxygen-poor environment

95. 3. Burial, causing maturation (the breakdown of organic matter into a liquid or gas) in a source

rock.

0 1. Relatively narrow temperature range, ~50 - 150 degrees C (also depends on time)

1 2. Temperature and duration determine type of hydrocarbon

2 3. Duration could last millions of years96. 4. Migration out of the source area into a permeable reservoir rock (e.g. porous and

permeable sandstone or limestone).

5. Trapping of fluids by an impermeable seal. (e.g. impermeable shale, limestone, orevaporite).

Why are oil and gas deposits often found in the crest of anticlines ? (see fig 22.4)

As oil and gas are lighter than water, they float to the top of the crest of the anticline.

How has the amount of oil produced and consumed in the U.S. changes over the past 50 years, and sowhat?

97. U.S. production of oil has been decreasing since 1970.98. U.S, consumption has been largely increasing since at least1949.


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We presently import over 50% of all we use in the U.S., more than at any other time inour history.

Approximately how long would the oil reserves last in the U.S. if we had no access to foreign oil? What

are the assumptions in your answer?Consumption Reserves Resources "lifetime"

US 5.9 bbl/yr 22.5 bbl ~105 bbl ~16 yrs

World 26 bbl/yr 1000 bbl 1550 bbl 60 yrs

bbl = billion barrels

Approximately how long will the oil reserves last in the world ? What are the assumptions in your answer?

See above.

How good are these assumptions and why?

Pretty good - as the Hubbert Curve predicts.

What is the Hubbert Curve and why is it important? How can it change?It tells us Approximately how long will the oil reserves last in the world

How can we increase the size of our oil and gas reserves ?

99. 1. Increase the price

100. 2. Lower the cost of production

101. 3. Find new conventional deposits

0 1. How much oil does the government estimate can be recovered from ANWR? 10.3 bbl

1 2. At present rates of US consumption, how long would that oil last? ~20 months.

102. 4. Get more out of old deposits (enhanced recovery)

5. Develop unconventional sources

Approximately how long would the oil from ANWR last at present rates of consumption in the US (think also about the assumptions)?

~20 months - assuming no increase in consumption or cost by 2025

Can increased energy conservation increase the size of our reserves?

No, but it can increase the lifetime of that resource.


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Approximately how much energy is lost between the well and the wheel of a car?

88%

What do all fossil fuels have in common ?Emissions of:

103. Carbon Dioxide (plus)

104. Carbon Monoxide

105. Nitrogen Oxides

106. Sulfur Dioxide

107. Volatile organics

Etc

What is the greenhouse effect ?

What is the main greenhouse gas (excluding water)?

Carbon Dioxide (CO 2)

What is the main source for that gas being added to the atmosphere today?

108. Burning of Fossil Fuels: 75%

109. Land clearing: 15%110. Manufacturing: 7%111. Fuel wood: 3%

How can we estimate global temperatures in the past, prior to instrumental readings?

112. 1.Coral Cores

113. 2.Tree Rings

114. 3.Ice Cores

4.Pollen

What do we know and not know about global warming?

What we know

115. Atmospheric CO 2 is increasing due to human activity.

116. CO 2 is only one of several greenhouse gases increasing due to human activities.


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117. Global temperature is rising

What we dont know

5. To what extent is increased CO 2 (and other greenhouse gases) causing global warming?

6. How might global warming affect global climate (including sea level)?7. What can we do about it?

Is it worth it?

Why is it inevitable we will shift from fossil fuels in the next 30 years?

The rollover of global oil production will happen around 2030.

What are some of our choices ?

118. Nuclear

119. Renewables, e.g.

0 Geothermal

1 Direct Solar

2 Wind

3 Tides

Hydrogen fuel cells?

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GEOLOY EXAM3