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LECTURE 1

Nature can jump up and hit us in the face (ex. Volcanoes, earthquakes, landslides, floods,

extraterrestrial impacts, etc.)

Civilization exists by geologic consent, subject to change without notice (Will Durant, historian)

Humans can jump up and hit nature in the face

Thomas Midgely (major negatibve effect on the earth)

- Invented leaded gasoline in 1921- Invented Freon, the first of the chlorofluorocarbons (CFCs) in 1930/1931

The world changes as we learn to see it in new ways. And the way we see the world depends on how

we use it.

View of earth from space led to increased awareness of the fragility of the Earth and the need to betterunderstand it

The President of the USA commissioned a study of the Earth System what do we need to know in

order to live in concert with this fragile Earth?

LECTURE 2

Five Reservoirs of Earth System:

1. Atmosphere2. Hydrosphere (Water and Ice)3. Solid Earth (Rocks and Soil)4. Life (Biota)5. Stars and Planets (tides, the sun, asteroids, etc.)- These things interact in complex ways

Earth Systems Engineering = Managing Earth Systems (For the use and convenience of people)

Humans move 4 times as much earth as other natural processes

In managing Earth systems, there is an ethical dimension

- You need to define your desired endpoints (i.e. you need to know where you are going)- Is the ultimate endpoint sustainability?

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Sustainable Development development that meets the needs of the present without compromising

the ability of future generations to meet their own needs

Sustainable Sufficiency living lightly within the soil as if the future mattered

The United Nations Development Programthe wealth of the worlds 200 wealthiest individuals is

equal to the combine annual income of 41% of the human population

LECTURE 3

Hazards, Disasters, and Catastrophes

Hazard: Something that may cause harm to people

There are both:

A) Natural HazardsB) AnthropogenicBoth A and B are often intertwined

There are landslides on Mars. Is there a hazardfrom Martian landslides?

YES! We have human property on mars.

We Need to Distinguish between Hazards and Resources

Resource: Something that is useful to us

Hazard: Something which may cause harm to people

All substances are poison; there is none which is not a poison.

Lets imagine a particular geographic location with a fixed human population

The right dose differentiates a poison from a remedy.

Poison -> Hazard Remedy -> Resource

Water as a Resource and as a Hazard

The amount of water we have available to us fluctuates. Drought vs. floods

When water crosses the damage threshold (boundaries in which amount of water can be characterized

as a flood or drought), water is considered a hazard. Else, it is considered a resource.

How do you decide what the Damage Threshold is?

1. Partly by empirical observations

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2. Partly by scientific studies

3. Partly by personal preferences

Consider pollution - pollution is a hazard. The very notion of pollution is culturally dependent. We

define what is or is not pollution

Lets imagine a particular geographic location with a fixed human population. Lets imagine that we

experience a hazard event (i.e. we go past the damage threshold)

What are the three main factors that control how severe the hazard event is?

1. Absolute amount (intensity) way too much or too little2. Duration of event too long3. Rate of Change too fast (not enough time to adjust to the change)

Rate of Change

e.g. sudden impact of a large meteorite -> can lead to mass extinction

e.g. burning, by humans, of oil, coal, and gas, causing an increase in CO2 emissions in the atmosphere ->

may lead to enhanced global warming

Note: Over time, there may be changes in human sensitivity to the hazard

-> some due to variations in physical events

-> some due to variations in socio-economic toleration

A) Secular change in the hazard

B) Increased intensity/variability

C) Decreased tolerance (shifts damage threshold lines -> makes them closer together)

Note: Also the consequences of synergy

Snow + Wind = Blizzard!

Each on its own might not be a big problem but together, you might have a disaster

LECTURE 4

After a hazard event, there are both losses and gains. Some people lose and some people gain.

When does a hazard event become a Disaster? Catastrophe? What factors distinguish a hazard event

from a disaster from a catastrophe?

1. Extent of human loss of life2. Extent of human injury3. Extent of monetary loss due to property damage4. Group versus individual

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a. Understand the Hazard (in general)b. Determine the risk from that hazard for the region of interest (PH x SH)

2. Risk Managementa. Determine ways to reduce PH and/or SH

i. Example: for an avalanche hazard in a given region, how can we reduce theseverity of consequences if the hazard happens to essentially 0? We can move

the settlement away from the hazard i.e. stay away from the hazard.

b. Conduct a Cost-Benefit analysisi. Determines what you can afford to do

1. Consider the economic, environmental, social, and personal choice ->what risks are we willing to take for what benefits?

a. E.g. Case study of chlorinating water in Peru -> USA studiesshowed that Cl (Chlorine) in water elevates the incidence of

bladder cancer -> so, following the USA Environmental

Protection Agency approach, many wells in Peru were NOT

chlorinated -> in an ensuing cholera epidemic, more than 3500

people were saved from bladder cancer by an early death

c. Implement mitigation techniques if warranted (and to the extent that you choose)Where should we spend whose money to undertake what programmes to save which lives with what

probability

programmes to improve which lives with what probability

What is a life worth?

Worth of a Life:

To whom is the life important?

a. Individual personb. Relativesc. Company looking at employeesd. Governmente. Society as a wholef. Young vs. oldg. Educated vs. non-educatedh. Present value vs. future valuei. Rich vs. poor

When you come to a fork in the road, take it

-> but worry about risks that can make you freeze up and do nothing

What is not possible is not to choose

Life is the art of courage and joy in the face of risk

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EARTHQUAKES

Seismic Risk Analysis and Risk Management for a proposed nuclear reactor near Kingston, Ontario

1. Understanding the hazarda. What causes earthquakes?b. Where do earthquakes occur?c. What energy do they release?d. What exactly causes damage?

LECTURE 6

Elastic Rebound Theory rigid part of Earth can store elastic energy

Therefore, earthquakes are associated with faults. Earthquakes happen when either:

a) A fault formsb) There is an episode of movement on a pre-existing fault

In both cases, stored energy is released.

For a big earthquake, fault motion needs to be only a meter or so.

Fault Terminology:

1. Strike-Slip Fault -> Horizontal Motion (ex. San Andreas Fault) (Medium Danger)2. Dip-Slip Fault -> Vertical Motion (generates a fault scarp)

a. Normal Dip Slip Down the Ramp (Least Dangerous)b. Reverse Dip Slip -> sub vertical motion Up the Ramp (Most Dangerous)

Note: Rivers are often found to occupy faults/fault zones (because the broken up rocks can be more

easily washed away) and we often build major dams on such rivers because the rivers make canyons

Focus: The point source of energy release on the fault

Epicenter: Location at the Earths surface directly above the focus. (Location at which the energy of the

surface will tend to be the most and cause the most damage)

Seismometers allow us to:

a) Detect the energy from a quakeb) Measure distance to an earthquake and thus locate itc) Measure the energy released during an earthquake

LECTURE 7

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How do we find the Focus of an Earthquake? In other words, how far away is the earthquake?

First, we need to know what seismic waves are, and how they behave.

Seismic Waves: Seismic energy waves radiate out from the focus of an earthquake as body waves.

Some body wave motion gets transformed into surface wave motion when the body waves reach the

surface.

Surface waves generally cause the most danger at surface.

Rayleigh Waves: Circular motion

Love Waves: Horizontal, side-to-side motion

Let us consider the body waves in more detail:

There are two kinds:

1. P-Waves: push-pull (compression-rarefaction)2. S-Waves: shear

What is the velocity of seismic waves? (how fast do they move) and What does the velocity depend on?

Vp (velocity of p waves) = sqrt ((k + 4/3mew)/p)

Vs (velocity of s waves) = sqrt(mew/p)

Where p = density and k and mew are elastic moduli

In the formula, k is the compressibility modulus (stress needed to compress the material) and mew is

the shear modulus (stress needed to change shape)

In words:

1. The more elastic a material is, the higher the seismic velocity.2. The denser a material is, the lower the seismic velocity.

So both P-waves and S-waves velocities change when they move into a different material.

1. P-waves travel faster than s-waves. (p-actually stands for primary, and s-for secondary)First energy received is p-waves, then you receive the first s-waves and then the surface waves come

last. This is because the speeds are not the same; p-waves travel fastest.

Seismic Velocities for Rocks at Earths Surface

P-Waves move at approx. 5.6 km/sec

S-Waves move at approx. 3.3 km/sec

Ex. For an earthquake in Toronto (approx. 250km away from Kingston), how long will it take until the

first p-wave reaches Kingston?

It will take approx. 1 minute.

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Think about

Thunder = S

and

Lightning = P

The longer the time gap between the flash of lightning and the peal of thunder, the farther away the

storm is.

So, finally: To measure the distance to an earthquake focus, we use travel times:

Empirically determined travel time curves.

For earthquakes: Since we didnt know seismic velocities at depth, we need to first create an empirical

travel time graph. For quakes of known location and time, obtain the P-S arrival time differences from

seismometers around the world.

To locate quake focus, you need a minimum of 3 seismometer stations.

LECTURE 8

Where do earthquakes occur?

At what depth do earthquakes occur?

Earthquakes can occur as deep as 700 km. 90% of earthquakes occur at less than 100 km deep.

Note: The radius of the Earth is approx. 6370 km

Only the outer part of the Earth is rigid enough (i.e. sufficiently Elastic) to experience Brittle Failure (fault

formation). Deeper in the Earth, it is too plastic (or liquid?)

How do we estimate energy released from an earthquake?

1. Measure the intensity (based on observed damage) e.g. the Mercalli Scalea. Subjectiveb. Varies with distance from epicenter

2. Measure the Richter Magnitude (a quantitative measure of energy released)a. Determined from the maximum s-wave amplitude on a seismogram (corrected for

distance)

b. Logarithmic scalec. It is an open-ended scale (we dont know how high it could go) (the largest earthquakes

ever recorded are approximately 9 on the Richter scale)d. Quakes less than 2.5 magnitude are not felt by humanse. Each magnitude integer step corresponds to approximately a 30-fold difference in

energy release

How much more energy is released in a magnitude 7 earthquake than in a magnitude 5 earthquake?

30 x 30 = 900 times more energy

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What do the Richter numbers mean in terms of Actual Energy released?

How would you figure that out?

Compare to known explosions (e.g. nuclear blasts)

How frequent are earthquakes?

Magnitude

< 3 -> over 100000/year

> 3 -> over 30000/year

> 6 -> 100/year

> 7 -> 20/year

Very few huge earthquakes

Lots and lots of small ones

LECTURE 9Earthquake Hazards:

What exactly causes damage?

1. Surface Faultinga. Structures on the fault will be disrupted by the tearing motionb. So dont build right on the active faults

2. Ground Shakinga. This is generally the greatest threat to buildings and peopleb. In General:

i. The closer you are to the earthquake, the greater the damageii. The greater the magnitude of the earthquake, the greater the damage

c. BUT this is modified by natural and anthropogenic conditionsi. Natural: nature of soils/rocks

ii. Anthropogenic: nature of the structures that we buildd. In a big earthquake, the shaking can be severe even 100s of kilometers away from the

epicenter

e. The amount of shaking also depends on the nature of the soil/rocks in the areai. Soft Soils (e.g. clay) shake more than stiff soils (e.g. sand) which shake more

than rock3. Ground Failure

a. Landslidesb. Liquefaction of Soils

i. Sand or clay soil that changes strength when shakenii. Can flow like a liquid

4. Tsunami

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a. Japanese words for harbor waveb. Colloquial: tidal wavec. Seismic sea wave generated by earthquake at sead. Wavelength up to several 100 km an hour at a velocity of 500 to 800 km/hour. Waves

pile up at shore to heights as much as 60 meters or more

5. Fires e.g. 1906 San Francisco fire6. Disruption of Water Supplies and Disease7. Human-Induced Seismic Hazards

a. Dam Constructioni. If the dam is constructed on a fault, it can potentially cause an earthquake

ii. Loading of earth by water changes the stress regime1. Earthquakes can happen

iii. Water infiltration below dam can lubricate faults1. Earthquakes can happen and there can be possible dam failures

b. Miningi. Underground blasting can destabilize the rocks

1. Can lead to earthquakes2. Threat of rock bursts3.

Material Amplification Effect:

Seismic Waves: Velocity changes when going from one medium to another. As P and S waves slow,

some of their energy is transferred to surface wave motion (i.e. increased shaking)

Rock Least shaking

Sand Soil intermediate shakingClay soil most shaking

Aftershocks:

Smaller earthquakes that occur soon after the main shock, with epicenters in the same area as the main

shock. They occur approximately minutes after to up to a year after. Aftershocks can cause collapse of

already damaged buildings.

LECTURE 10-13

Tsunami Causes

1. Seafloor Earthquakes2. Underwater landslide3. Collapse of the flank of a volcano into the sea4. Submarine volcanic explosion5. Impact of meteorite into the ocean

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Assess Seismic Risk of Area

a) Locate and determine nature of faults in the areaa. Look on the ground, and from the air (and space) but there can be hidden faultsb. Set up seismometers to help locate faults

i. Only effective for faults that have moved since seismometers were set upii. Note: Fault Zones are very complex

b) Study the history of earthquakes in the areaa. Which faults are active and how often do BIG earthquakes occur in our region of

interest

b. Set up seismometers to collect historical datai. Gives us an idea of which faults are most active

ii. Gives us some idea of the frequency and magnitude of the earthquakes1. Critical to collect as long a seismic record as possible. Where are the

high earthquake prone zones?

2. Determine recurrence interval for Big earthquakes in the area. Bigrefers to greater than magnitude 6. How do we determine the

recurrence interval for big earthquakes?

a. Look at human historical records which goes back beforeseismometers

b. Dig trenches and pits on the active faultsc. Look for evidence of ancient tsunami and ground

elevation/subsidence

i. Buries swamps1. Date the dead organic matter (c-14 method)

and this gives us the age of the earthquake3. Construct probability maps and earthquake based maps to help future

planning

PART 2Determine the recurrence interval

Does every fault produce earthquakes?

NO! Some are inactive which means that it has not moved in the last two million years. Some are

potentially active which means it has moved in the last 2 million years. Some are active which means it

has moved in the last 10,000 years.

Relative Time

1. Law of Superpositiona. For sediment layers, oldest layers are on the bottom, youngest on top

2. Law of Cross-Cutting Relationshipsa. Fault cuts across the layers therefore, the fault is younger than the layers therefore you

can determine the relative age of the fault depending on the layers of soil

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i. We can date old earthquakes (carbon-14 dating)ii. Peat layers contain dead organic matter. The time since the organic matter died

can be determined by the Carbon-14 method. So, the absolute age of the

faulting event can be determined

Carbon-14 DatingOnce dead, the amount of Carbon-14 in the tree decreases at a fixed rate. We measure the ratio of

Carbon-14 to Carbon-12.

Half-Life:

Length of time for half the radioactive element to decay.

1 half-life for carbon 14 is approximately 5730 years.

Carbon 14 dating (and other radiometric dating methods) can be used to determine when a fault last

moved (if your seismometers havent already told you the answer)

But, it is a subjective determination to decide if a particular movement event was a big earthquake orjust a small one. We can turn to other evidence of big earthquake activity that is less subjective. We

can look for evidence of ancient tsunamis and ground elevations/subsidence

Example: Los Angeles, California

9 Major earthquakes in 1400 years, therefore, the recurrence interval is 1400/9 = 160 years.

The last big earthquake was in 1857. Therefore, the earthquake is due now. However, note that the

events are not evenly spaced.

Assess Seismic Risk of Area

a. Locate and determine nature of faults in the areab. Study history of earthquakes in the areac. Determine the geologic and geographic factors in the area

a. Map out locations of rock, sand soils, clay soils, etc.i. They have variable shaking characteristics

GEOL 106 MID-TERM Thursday March 3, 2010 7:30 to 9:00 pm

LECTURE 14-16

Assess seismic risk of area:

Determine the Geologic/Geographic factors in the area

1. Map out locations of rock, sand soils, clay soils, etc.

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a. They have variable shaking characteristics2. Map out zones of sand and clay that are prone to liquefaction3. Map out cliffs/hills that are at risk of landslides4. Map out tsunami risk zones

a. Shore lines of oceans and lakesDetermine human interactions with the potential hazard in the area

1. What is the distribution of the population in the areaa. Particular attention to proximity of people to high-risk zones

2. What is the nature of the human infrastructurea. Where are the buildings and rocks with respect to high-risk zonesb. What are the buildings made of, and how are they designed

Now, after all of what we talked about, you can then create a full picture of the seismic risk for your area

of interest

- Write reports- Try to quantify it- Make risk maps

Risk Management

1. Understand the Hazard (Risk Analysis)2. Determine the risk from that hazard for the region of interest(PH x SH) (Risk Analysis)3. Determine ways to reduce PH and/or SH4. Do a cost benefit analysis

a. Determine what you can afford to do5. Implement mitigation techniques if warranted

Determine ways to reduce the probability of the hazard happening and the severity of the hazard (PH x

SH)

To try reducing the severity of the hazard:

1. Apply land-use planning and zoninga. Use high risk areas for low population useb. In particular, dont build in areas of soft soil or soils that might liquefy

2. Apply stringent building codesa. Choose appropriate building materials

i. There are good and bad materialsii. Examples of good materials are wood, steel, reinforced concrete (steel-

reinforced concrete

1. The good materials are all flexible

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iii. Limit population centers along earthquakeiv. Provide tsunami education/training

6. Try predicting earthquakesa. Long term

i. Determine recurrence intervalsii. Look for seismic graphs

1. These are high risk areas (the stored energy is not being released (thefault is locked) and when it finally does get released, watch out)

b. Short termi. Difficult (impossible) to pin point precise times of upcoming earthquakes

1. Because earthquake behavior is chaotic, short term prediction is notlikely to work

ii. However, changes preceding an earthquake might provide some warning1. The main change as stress builds up is the formation of micro-cracks in

rocks (a process known as dilatancy) (i.e. expansion in volume by cracks

opening up)

a. This can lead to:i. Ground bulge

ii. Micro seismicity (small little earthquakes) andforeshocks (smaller earthquakes that happen before the

big earthquake)

iii. Increase in radon levels in wellsiv. Drop in water levels in wellsv. Drop in seismic velocity

To try to reduce the probability of the hazard:

7. Try controlling earthquakesa. Slow creep on fault in Hollister, California

i. Possibly because of the mineral talc that lubricates the faultb. Perhaps lubricate faults with water to possibly control earthquakes?

i. Big risk that you can trigger a really big earthquakeLECTURE 14-16

LECTURE 17-19

Where do earthquakes occur?

90% at depths less than 100km (the lithosphere is 100km thick)

10% at depths between 100 and 700km

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Three kinds of plate margins:

Constructive (Pulling Apart Normal Dip Slip Faults), Destructive (Colliding Into each other Reverse Dip

Slip Faults), and Transform (Sliding Strike Slip Faults)

Bulk of earthquakes occurs on plate boundaries

Intra plate earthquakes can occur however:

Intra plate earthquakes are earthquakes that occur away from plate margins (represent only about 1%

of all earthquakes)

Most intra plate earthquakes occur former plate margins

The S waves stop at the boundary of the outer core telling us the outer core is liquid

The Silly Putty Mantle

The mantle, although solid, convects plastically. It behaves like Silly Putty (Elastico-Plastic). Plastic

behavior during slow stress application. Elastic behavior during rapid stress applications.

Volcanic Risk

Igneous Rocks

Formed from the cooling and crystallization of magma (magma = liquid rock)

Where does Magma Originate?

Mainly in the upper mantle (down to approximately 200km)

Sometimes in the crust

Consider the plate tectonics framework

Volcano Zones

1. Constructive Plate Marginsa. Divergent

2. Destructive Plate Marginsa. Convergent

3. Hot Spotsa. Most commonly not at plate boundaries

Magma generally rises due to its lower density

Some magma reaches the earths surface (extrusive)

Most magma crystallizes beneath earths surface (intrusive)

Important Note:

Magma contains dissolved gasses

Generic Approach to Risk Analysis and Risk Management

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Risk Analysis:

1. Understand the Hazard2. Determine the risk from that hazard for the region at interest (risk =Ph x Sh)

Risk Management:

1. Determine ways to reduce Ph and/or Sh2. Do a cost-benefit analysis3. Implement mitigation techniques if warranted

Volcano Zones

1. Constructive plate margins (divergent)2. Destructive plate margins (convergent)3. Hot spots (most commonly not on plate boundaries ex. Hawai)

Dealing with Volcanic Risk:

We first need to consider the nature of magma of different compositions

Chemical Composition:

Magmas differ in the proportion of elements -> results in rocks of different colors -> and magmas with

different properties

More Si + O and less Fe + Mg -> rock is whiter/pinker -> Felsic Rock ex. Rhyolite

More Fe + Mg and less Si + O -> rock is blacker -> Mafic Rock ex. Basalt

Magmas:

Felsic Intermediate Mafic

High Viscosity (sticky) Intermediate Viscosity Low Viscosity (very fluid)

High Si Intermediate Si Low Si

High H2O (>5%) Intermediate H2O (1 to 5%) Low H2O ( Flows easily

High Viscosity -> Does not flow easily

Magma, when it comes out of the ground, will be in one of two forms:

1. Lava (liquid)2. Pyroclastic material (hot particles)

Magma reaches the surface by coming through either

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1. Fractures (fissures)2. Volcanic cones

Fractures (fissures)

- i.e. cracks (where a dyke reaches surface- mostly involve mafic lava (i.e. basalt)- results in extensive lava sheets due to low viscosity ex. Iceland- these are calm eruptions

Dangers of Fissure Eruptions

- generally quite safe- major eruptions can generate atmospheric effects from SO2 gas (and CO2 gas) (ex. Laki eruption

in Ireland)

- in particular, enormous flood basalt events may be catastrophic (linked to mass extinctions) (ex.65 and 250 mya)

Volcanic Cones

- pipe like conduit and vent brings magma to surface- eruptions range from calm to violent

o depends on magma compositionVolcanic Cones

3 Main types

1. Cinder Cone the kind of material is pyroclastic2. Stratovolcano (composite cone) material is lava and pyroclastic (felsic to intermediate

material)

a. They have a composite nature with layers of pyroclastic material and layers of lava thatare intertwined

b. Similar shape but much larger than cinder cone volcanoes3. Shield Volcano material is lava which makes mafic rocks (calm eruptions)

a. Shield volcanoes are much larger than stratovolcano but have a very flat shapeb. They have the shape of a roman shield

The most dangerous types of volcanoes are stratovolcanoes

- Their magma composition is felsic or intermediateo Therefore, the magma has

High viscosity High water content

o This leads to High steep sided volcanoes

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1. Ashflow (pyroclastic flow)a. Nuee ordente glowing cloud

i. Travel downslope at up to 150km/hii. Can travel more than 10kmiii. Ex. Mt. Pelee 1903 AD

b. Pyroclastic surge/blast (lateral blast)i. Travel 300km/h or faster

ii. Can travel more than 10kmiii. Ex. Mount St. Helens

2. Lahars (volcanic related mudflow)a. Ash on flanks of volcano mix with melted snowb. Flow down steep flanks of volcano and river valleys over distances greater than 100kmc. Ex. Nevada del Ruizd. Ex. Mount Saint Helens

Other Potential Dangers

1. Tsunamia. For island arc volcanoesb. Sudden explosion can trigger a tsunami

i. Ex. Krakatoa2. Poisonous gases

a. Various gases can create problemsi. Ex SO2 can generate sulfuric acid in atmosphere

ii. Ex. CO2 heavier than air3.

Caldera collapse and supervolcanoes

a. Supervolcanoes are rare explosive supereruptionsb. Can cover whole continents with ashc. Can have truly global catastrophic events (climate and weather)d. Ex. Eruption of Toba and Yellowstone (74,000 and 640,000 years ago respectively)e.

What is the Global Long Term Recurrence Interval for Supereruptions?

- Like magnitude 9 earthquakes, they are rare- Supereruptions are very, very rare

o Average of 1 every 100,000 yearsthey probably present the greatest natural hazard to mankind in terms of the severity and longevity of

impactthe ultimate geologic hazard S. Self and S. Blake (2008)

Assess Volcanic Risk of Area

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A) Locate and determine nature of volcanoes in the areaa. Volcanoes are generally easy to findb. Look at world volcano maps (plate tectonics)c. What kind of volcano?

i. Shape1. Fissure2. Shield volcanoes3. Stratovolcanoes

ii. Composition of the rock (mafic or felsic)B) Study the history of volcanoes in the area

a. Past behavior is key to future behavior (usually)b. Nature of eruptive materials (any tephra? Pyroclastic flow deposits? Lahars?)

i. Assess magnitude of eventsc. Determine recurrence intervals

i. Ex. Carbon dating on trapped wood and K-Ar dating)ii. produce a frequency-magnitude curveiii. construct probability mapsiv. active vs. dormant vs. dead

C) determine geologic/geographic factors in the areaa. Where are the valleys and river channels?

i. routes for pyroclastic flows and laharsii. what are prevailing wind directions

1. most likely way air fall ash will goiii. what are the risks of a tsunami?

1. Volcanoes in island arcsUse all this information to produce hazard maps

Determine potential human interactions with the hazard

- Population distribution- Nature of human infrastructure- Proximity of people to high-risk zones

Carry out Preventative Measures (i.e. minimize damage) (after cost-benefit analysis)

a)

Apply land use planning and zoninga. Avoid high risk areas

b) Apply building codes/build structures to minimize damagea. Not as easy to do as for seismic riskb. Roof design to withstand ash fallc. Concrete channel ways in valleys to control lahars and pyroclastic flows

c) Set up emergency response plans

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a. Educationb. Evacuation plans (critical because there is usually plenty of warning time)c. Have emergency services in place

d) Try predicting volcanic eruptiona. Generally quite successful due to the nature of volcanic behavior

i. Long Term:1. Past history is a key to future behavior

ii. Short Term:1. Magma rises up from 5km deep (or more) over a lengthy time (weeks,

months, years)

a. Use methods to detect movementiii. Monitoring Methods

1. Seismologya. Magma pressure on rocks causes them to shift creating

earthquakes

i. Locate earthquake foci to determine footprintb. Measure the surface ground deformation (movement)

i. Ex. Bulges, etc.ii. Use GPS to measureiii. Use tilt-meters to measureiv. Use radar interferometry

c. Gas monitoringi. Volume of CO2 and SO2

ii. Gas volumes increase before eruptive eventWhat Is Good About Volcanoes?

1. Builds up land (makes continents)2. They are beautiful (tourism)3. Geothermal energy4. Good soil for agriculture5. Generate ore deposits (precious metals)6. Atmosphere + hydrosphere effects

a. Partly responsible for waterb. CO2 producer (saved us from snowball earth)

7. Involved in life development

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Mass Wasting

The downslope movement of solid Earth materials under just the influence of gravity.

How do we Minimize Damage from Landslides?

1. Understand the hazardLandslides and Risk

Earthquakes and Volcanoes predominantly at plate tectonic boundaries

Landslides landslides can occur anywhere there are slopes

What determines whether a landslide occurs or not?

1. Slope steepness2. Nature of the material

a. Soil/aggregates (loose stuff)b. Solid rock

i. How much friction?ii. How much internal strength?

3. Triggering effectsa. Ex. Rainfall, earthquakes, human action, etc.

Leads to a wide variety of down slope movements

Classification of Landslides

Your textbook talks of 4 variables:

a) Mechanism of movementb) Type of materialc) Amount of water presentd) Rate of movement

The classification scheme incorporates all of these

My scheme is a bit different from that in the textbook (Page 112)

Rotational Slip (Soil)

Translational Slip (Rock)

Permafrost permanently frozen ground up to 100s of meters thick

Active Zone ice melts in summer

a) Locate and determine the nature of potentially dangerous slopesa. Studies on the groundb. Use of air photographs

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b) Study the history of land slides in the areaa. What kind of mass movement was there in the past?b. What is the recurrence interval for the events?

i. Use Carbon 14 dating of dead organic matterc) What is/are the geologic/geographic controls?

i. Nature of rocks/soilsii. Slope steepness, etc.

d) What are the interactions of people with the slopes?i. Population distribution

ii. Infrastructure (roads, buildings, dams, etc.)e) For a particular slope that you are worried about, carry out a safety factor analysis

a. This determines the probability of failure of that slope (Ph)b. How safe is the slope?

In Managing Risks in an area:

Try to reduce Ph and/or Sh

For earthquakes and volcanoes, we have little or no control on Ph, so most effort goes toward reducing

Sh

For landslides, we can actually reduce the probability of the hazard happening (Ph)

Slope Stability and the Safety Factor Concept

How exactly do we determine the probability of failure of the slope? (Ph)

Use the example of an open-pit mine to explain this

Goal To mine out the granite porphyry as cheaply as possibleDig pit walls on an angle so it doesnt cave in. How steep can you make the pit wall?

Angle of potential failure plane = alpha

Consider a block, of weight W, sitting on a slope of angle alpha

Weight of a block (w) = volume (v) x density (e) x acceleration due to gravity (g)

W = (w)(v)(e)

Physics of Slope Stability of a Rock Mass

Safety Factor a measure of the stability of the slopeSafety Factor (S.F.) = Resisting Force / Driving Force

If SF > 1, slope is stable

If SF < 1, slope is unstable

How do we determine resisting force and driving force?

What determines whether a landslide occurs or not?

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1. Slope Steepness2. Nature of the Material

If a box is sitting on a flat board, W = N

If a box is sitting on a vertical board, W = T

Otherwise, some of the weight is acting tangent and normal to the board

Driving force = T

Resisting force = N

Sin alpha = T/W

So: T = W x sin alpha

Cos alpha = N/W

so: N = W x cos alpha

Therefore, driving force = T = W x sin alpha and resisting force = N = W x cos alpha

Consider the Different Terms in the Safety Factor

1. How do we measure them?2. What are the possible errors that arise in measuring them?3. Which terms are most critical?4. Is there anything that we are missing in the analysis?

Safety Factor = (CA + (W x cos alpha x tan theta)) / w x sin alpha

Safety Factor = Resisting Force / Driving Force

A) Potential failure plane angle (alpha)a. The steeper alpha is, the lower the S.F. isb. The safety factor is very sensitive to a change in alpha (angle of potential failure plane)c. Therefore, a small change in alpha results in a big change in the safety factor

B) In rocks, potential failure planes are planes of weakness and are also known as discontinuitiesa. These planes of weakness include

i. Sedimentary bedding planesii. Faultsiii. Joints

1. Joints are cracks in rock where the blocks of rocks on either side of thecrack have not moved with respect to each other

2. If the blocks have moved, it is a fault3. Joints can form by:

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a. Release of pressure when buried rocks are brought to Earthssurface during weathering and erosion

b. Squeezing of rocksc. Shrinking of igneous rocks as they cool following crystallization

C) Weight of the potential failure block (w)a. The larger w is, the lower the Safety Factor isb. Increasing the slope of the pit wall decreases the Safety Factorc. Loading weight on a slope will decrease the Safety Factord. Weight = volume x density x gravity

i. During an earthquake, the gravity value can be locally changed because duringthe earthquake, the ground moves

e. The effect of a change in weight on Safety Factor is not very great. Even a big increasein weight only causes a small decrease in Safety Factor but, if you are already near

failure, a weight increase might push you over the edge

D) Different materials have different strengths but there are problems of measuring strength (thestrength terms are C and tan theta)

a. What is the relationship between lab experiment and natural situation?b. What is the relationship between the intact rock versus the rock mass?c. What if there are thin, weak, rock layers that you fail to notice or sample?d. Weathered vs. un-weathered rocks

E) The strength of a material can decrease by:a. Vibration affecting sensitive claysb. Sensitive clay/quick clay

i. Changes strength dramatically when vibrated by earthquakes or heavymachinery or during slip

ii. It liquefiesc. The Safety Factor is extremely sensitive to a change in tan theta, but not very sensitive

to a change in C

i. A decrease in tan theta and/or C leads to a decrease in the Safety FactorSlope Stability and Water

Water can infiltrate into the ground (groundwater). This can decrease the stability of slopes by:

1. Adding extra weight2. Creating pore pressure that causes uplift

Safety Factor = CA + N x tan theta / w x sin alpha (without water)

Safety Factor = CA + (N-P) x tan theta / w x sin alpha (with water)

Where P = pore pressure

Therefore, adding water causes instability.

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Water is absolutely critical.

Linkages

- Earthquakes and volcanic eruptions can cause landslides- Large landslides can trigger tsunamis

Human Impacts

1. Urbanization in land-slide prone regions2. Tree cutting

a. Removal of vegetation3. Global climate-change effects4. Dam construction

Mitigation Techniques

1. Land use planninga. Stay away from unstable areas

2. Stabilize the slope (reduce Ph)a. Drainage controlb. Rock bolts (slope support)c. Retaining walls; screens (slope support)d. Cut benches/create steps on the slope

i. Helps localize where the failure occurse. Reduce slope gradient by grading

3. Set up emergency response plansa. Educationb. Emergency services (most critical for avalanches)

4. Try predicting landslidesa. Carry out safety factor analysesb. Monitor slopes using

i. Tilt metersii. Monitoring stakesiii. Geophonesiv. GPSv. Studies of water contentvi. Studies of weather

Note Cost/Benefit of Landslide Mitigation

The benefit/cost ratio varies from 10 to 2,000

Therefore, for every dollar spent to mitigate the probability of the hazard happening, you save between

$10 and $2,000. Thus, it is very successful and cost effective.

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Water as a Hazard

1. Surface Watera. Flooding (over abundance)b. Drought (scarcity)c. Contamination

2. Ground Watera. Floodingb. Scarcityc. Contaminationd. Can trigger landslides, earthquakes, etc.

Ground Water Contamination

Water can move underground and carry toxic chemicals

We are interested in a sit in which precipitation falls on a waste dump and the water moves down and

begins to contaminate (leachate contamination)

We want to know:

1. In what direction will it move?2. How fast will it move?

As an example:

Lets suppose that our open pit mine from our slope stability analysis is used to store garbage once the

ore is mined out. Where is the potentially toxic leachate going to go?

How can water move through solid soil and rock?

The material must have empty spaces that are connected to each other. Ex. Sand soil or sandstone,

cracked or jointed rock. Such material can act like a sponge.

Close up of Sand Soil

Sand soils are made up of sand grains and empty space.

Porosity: The amount of empty space in the material

Permeability: A measure of the ease with which water can flow through the material

Such material can act like a sponge.

For high permeability, the pores need to be connected. Can you think of a rock that has high porosity

but very low permeability? Pumice

Permeability can range from 0 to 100%.

Some examples:

Clay + claystone = low permeability

Sand + sandstone = moderate to high permeability

Gravel + conglomerate = very high permeability

Most igneous rock = very low permeability and depends on fracture density

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Karst limestone = can be very high (100%) permeability

Fault zones = can be very high permeability

Ok, lets look at a simple situation: permeable sand sitting on impermeable rock and then let it rain for a

week and see what happens.

The water will percolate the sand and will fill up the section of permeable sand. It will not be able tosaturate the impermeable rock. Therefore, the sand fills part way up with water. The water table

separates the zone of saturation and unsaturation. The zone of saturation is the part of the permeable

substance that is filled up. The zone of unsaturation is the part of the permeable substance that is not

filled up.

The water table is the boundary between the saturated and unsaturated zones. In our example, we can

find the water table by drilling a well.

If the water table is flat (horizontal), the water will not flow laterally. But, if the water table is not flat,

the water will flow laterally.

Push up one side of a table. What direction will a marble roll down on the table top? The steepest side.

To Find Groundwater Flow Direction:

Drill several wells and measure the height of the water table for each well. Draw a map and draw on it

lines of equal water-table height. (i.e. you contour them)

Determine water-flow direction using 2 rules:

1. Water flows from higher water-table levels towards lower levels2. Flow is always at right angles to the lines of actual water-table height

Groundwater Movement

1. In what direction is it moving?2. How fast is it moving?

a. Take a sample to the lab and pump water through iti. Velocity depends on two things

1. Permeability of the material (K)2. The force of the water from the tap (Hydraulic Gradient)

ii. Pump water out of the ground and create a draw-down cone1. Great for measuring permeability (K) and getting an idea of velocity

iii.

Put a tracer such as a dye into a well and see how long it takes to get intoanother well

Rates of Groundwater Flow Slow! Only a few cm/day. (Compare to rivers at km/hour)

Good: Stores water underground (acts like a dam)

Good: Allows purification of water over short distances.

Bad: Once contaminated, it takes a long time to flush out.

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Climate Change

Weather: Short-term (days to weeks) variations in atmospheric conditions (temperature/rainfall/etc.)

Climate: Long-term (years/decades/centuries) variations in atmospheric conditions. Ex. Tropical vs.

temperate vs. Arctic climate

The Rock-Record tells us that there certainly has been climate change in the past. Ex. Look at

Kingston, Ontario which was covered in ice sheets 20,000 years ago and covered in shallow tropical seas

500,000,000 years ago.

Why Might Climate Change?

1. Natural Causesa. Ex. Increased solar luminosity (sun getting brighter)b. The sun provides more heat as time passes

2. Anthropogenic (Human-Induced) Causesa. Burning coal/oil/gas perhaps adding CO2 to the atmosphere and heating it

Global warming already exists. Greenhouse gases heat our atmosphere and they include:

H2O (water), CO2 (carbon dioxide), CH4 (methane), NOx (Nitrous Oxides), O3 (Ozone)

Without them, the average Earth-surface temperature would be -20 degrees Celsius

Specifically, enhanced global warming caused by humans burning coal, oil, and gas.

Is There Enhanced Global Warming?

1. Have humans been changing the amounts of these greenhouse gasses in the atmosphere?a. Particularly carbon dioxide

2. If so, is it leading to a warming of the atmosphere3. If 1 and 2 are true, then what is the rate of change?

We will look at the hazard posed by enhanced global warming as an example of climate change. How

does the hazard of climate change differ from other hazards we have discussed in the course?

Generally, it is more complex and less-well understood.

Is there enhanced global warming?

1. Is there an increase in atmospheric carbon dioxide due to human action?Does all of the CO2 remain in the atmosphere and does it cause warming?

We need to look at the recent history of atmospheric CO2 to determine if humans have affected it.

Recent = The last 2 million years. How do we measure this?

1. Measure it directly day after daya. We have only been doing this since the 1950s

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b. Shows positive correlationThe saw tooth ups and downs in the CO2 levels are due to seasonal variations.

In the winter, trees are dormant. Therefore, CO2 is not being extracted from the atmosphere.

In the spring/summer, trees are active. Therefore, CO2 is being extracted from the atmosphere.

Photosynthesis in Plants

Carbon Dioxide + Water --> (Sunlight) Sugar + Oxygen

2. To go back farther in time, measure CO2 in air bubbles trapped in ice sheets in Antarctic andGreenland glaciers.

a. This takes us back to over 400,000 years agob. We can count the annual ice layers as we go deeper just like counting tree rings

So:

a) Todays level of atmospheric CO2 is way higher than it has been for the last 400,000 yearsb) The dramatic rise in atmospheric CO2 began with the Industrial Revolution

Conclusion to First Question:

Is CO2 in the atmosphere increasing due to human actions? Almost certainly yes.

Second Question:

Has the human-induced atmospheric CO2 increase led to an increase in atmospheric temperature?

How do we determine global surface temperatures in the past?

1. Look at historical temperature readings (taken by humans)a. Since 1880 AD, there appears to have been an increase of around 1 degree centigrade

2. Look at ice coresTo determine atmospheric temperatures from before humans were around, we must look at oxygen

isotopes in the ice cores.

Ice is H2O. There is heavy 18O and light 16O. When it is warmer, the heavier 18O evaporates from the

sea because there is more energy to pick up the heavy oxygen. Thus, the snow falling on ice sheets has

a larger 18O to 16O ratio when it is warmer.

It appears that when CO2 is high, the temperature is high and when CO2 is low, the temperature is low.

But maybe its not the increased CO2 that has caused the warming. Therefore, we need to consider all

the factors that have changed that might have forced the temperature to increase (ex. Solar luminosity).

Forcing Factors

No doubt about it: Human produced greenhouse gases such as CO2 dominate.

So:

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Second Question: Has the human-induced atmospheric CO2 increase since the Industrial Revolution led

to an increase in atmospheric temperature? Probably.

IPCC computer models predict an atmospheric temperature increase of somewhere between 1.8

degrees and 4.0 degrees Celsius by the year 2100.

We can also look at oxygen isotope ratios in fossil shells which are made up of calcium carbonate in mud

layers in lakes. This can take us back to over 1 million years ago.

Third Question:

How do we determine if the rate of temperature increase since the Industrial Revolution has been

unusually (and eventually dangerously) rapid.

We can look back at the geological record of temperature change and their consequences.

As an example, we will look at the younger dryas event about 12,000 years ago.

Younger Dryas Event:

We were warming up after the last glaciation, reaching temperatures near present values about 13,000

years ago. Suddenly, (in as little as a few decades), Europe plunged into severe cold (the younger dryas

event).

What caused this sudden cooling?

Probably, the warming had produced massive amounts of cold, fresh meltwater from the ice sheets that

suddenly was released into the North Atlantic Ocean. This resulted in the shutting off of the Oceanic

Conveyor Belt which normally brings warm water into the North Atlantic to keep Europe warmer.

So, one fear is that the anthropogenic warming since the Industrial Revolution may melt massive

amounts of the Greenland Ice Sheet which could trigger another Younger Dryas type of event which

could happen equally rapidly as the original event (a few decades or less).

For natural effects causing climate change, lets look at the whole history of the Earth. This will

provide us examples of the complex interaction of the 5 reservoirs of the Earth System.

Five Reservoirs of Earth System:

1. Atmosphere2. Hydrosphere (water and ice)3. Solid Earth (rocks and soil)4. Life (biota)5. Stars and Planets

First Example: What caused the alternating glacial-interglacial periods over the past 2 million years?

Sun-Earth orbit relationships (Milankovitch Cycles)

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100,000 year cycle: out-of-roundness

41,000 year cycle: tilt

20,000 year cycle: wobble

But why has the Earth been in a Glacial mode for the last 2 million years?

This probably occurred because of Plate Tectonics.

1. Joined North and South America (which affected ocean currents)2. Pushed up Himalayas Mountains (which affected air flow and increased the rate of weathering)

CO2 Rock Weathering Cycle

CaSiO3 (rock) + CO2 (air) CaCO3 + SiO3 (washed down in the sea)

Then: Life forms build shells of CaCO3 and form carbonate deposits on the sea floor.

The limestone is extracting CO2 out of the atmosphere, thus, the atmosphere cools.

Another example of the role of life on the atmosphere:

Times of peak coal formation

1. Approximately 300 million years ago (first major land plants)2. Approximately 80 million years ago (first flowering plants)

Plants in swamps die, get buried, and turn into coal and then they extract carbon from atmosphere and

this therefore lowers atmospheric CO2, and increases atmospheric O2

Photosynthesis in plants: Carbon Dioxide + Water (sunlight) sugar + oxygen

6H2O + 6CO2 (sunlight) C6H12O6 + 6O2

The very high oxygen levels led to gigantic animals

Other Natural Causes of Climate Change

Volcanoes:

a) Pump CO2 into atmosphere which causes a warming effectb) Pump ash into atmosphere which has a cooling effect

Meteorite/Comet Impact:

Potentially dramatic and could cause rapid climate change. This can lead to mass extinctions. Ex. 65

million years ago dinosaur extinction.

Another Example:

We also have evidence that the early earth had almost no free O2 in the atmosphere. A special rock,

called banded iron formation, is restricted in age. Its emergence marks an increase in O2 in the

atmosphere.

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Banded Iron Formation (BIF) is our main source of Iron. Huge BIF deposits formed between 2.3 and 1.9

billion years ago.

Without O2: Iron is very soluble in water.

With O2: Iron is not very soluble in water. It precipitates out as iron oxide minerals such as magnetite

(Fe3O4) making banded iron formation.

Oxyatmoinversion: The atmosphere went from Oxygen poor to Oxygen rich around 2.4-1.8 billion

years ago. This caused Iron to be precipitated out of seawater to make Banded Iron Formation.

Where did the Oxygen come from?

Photosynthetic life (planktonic cyanobacteria).

The oxygen levels rose significantly approximately 800 million years ago (Metazoa).

So: In the first billion years of the Earths history, the atmosphere was:

Very poor in oxygen (O2) but very rich in Carbon Dioxide (CO2)

But, how do we know it was CO2 Rich?

Because water wasnt frozen back then.

If we had no atmosphere at all, Earths surface temperature would be minus 20 degrees Celsius.

What kept the early Earth Warm?

An atmosphere rich in CO2 (like Venus). But that had to change or we would have gotten too hot.

Early atmosphere: CO2 rich and O2 poor. This kept the surface warm (greenhouse effect)

Later atmosphere: CO2 poor and O2 rich due to life forms.

Where did the oxygen come from? Photosynthetic life.

Consider the Carbon Cycle:

Life moderates the surface temperature.

Role of life in Atmospheric Change: Examples

1. Humans burning fossil fuelsa. Increasing atoms CO2b. Enhanced global warming

2. Marine organisms building CaCO3 shells to make limestonea. Reducing atoms CO2b. Cooling atoms

3. Coal formationa. Extracts CO2 from atomsb. Stores C as coalc. Decreases CO2 and increases O2 in atoms

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4. Early photosynthetic cyanobacteriaa. Produce O2 in early atomsb. Create oxyatmoinversion (early earth no O2)

In 1979, James Lovelock developed the Gaia hypothesis. A bold statement recognizing the Earth as a

complex Earth System with life being an intimate player in affecting Earth behavior.

Gaia Theory: All life and all the material parts of the Earths surface make up a single system, a kind of

meta-organism, and a living planet. James Lovelock

a tightly coupled system whose constituents are the biota, the atmosphere, the oceans, and the

surface rock with self-regulation of important properties like climate and chemical composition

Part of the Gaian Theory: Life moderates the Earths surface temperature. This helps to maintain

conditions in which life can exist.