geology notes.docx

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Department
Geological Sciences and Geological Engineering
Course
GEOL 106
Professor
Prof.
Semester
Fall

Description
Introduction to earth system science and earth system management / engineering-lecture 2 Fred Hoyle, Edgar Dean Mitchell “the world changes as we learn to see it in new ways. The way we see the world depends on how we use it.” From ‘hand’ end: technology and limits of nature 1993 by David Rothenberg • Number of U.S.A. laws on environmental protection has increased dramatically from 1970 -1990, The curve on the graph bends in the time when astronauts first landed on the moon “we made all this way to the moon to finally disc,over earth.” By William A. Anders Apollo VIII astronaut • Mark Garner, the first astronaut, member of parliament, running for the leadership of liberal party • View of the earth from space led to increased awareness of the fragility of the earth and the need to better understand it • The president of the US commissioned a study of the earth system  What do we need to know in order to live in concert with this fragile earth? • The earth system is a set of interacting sub systems  earth system science How its parts and their interactions evolved, how they function today and how they may be expected to function in both the near and distant future. In this light the earth system is seen as a set of interacting subsystems. Change in one component can propagate through the entire system. FIVE RESERVOIRS OF EARTH SYSTEM Atmosphere, hydrosphere (water and ice), solid earth (rocks and soil), life (biota), stars and planets * Earth systems engineering =managing earth systems * The earth is increasingly a product of human engineering” “The earth as it now exists is a human artifact” “it reflects the (frequently unintended and unconscious, but nonetheless real) design of a single species” – Brad Allenby  claims that humans have been conducting earth system engineering from the start Continued (lecture 3) Lead contamination in Greenland glacier • The amount of lead contamination significantly increased after the unleaded gasoline. How does past E.S.E. compare to the uture E.S.E. • Two main issues : scale  in past it was more local/less global, intent in past, regional/global effects were unintended and unanticipated • Aral sea was shrinking in the year 2010 and all that remained were three small water bodies  Water was being sucked away and the had impact on the climate to change Thomas Midgely • Had more impact on the atmosphere than any other single organism in the earth history 1921 o found that tetra ethyl lead reduced engine knocking, he invented leaded gasoline o 1930-31, invented Freon the first of the chlorofluorocarbons (CFCs)  created the ozone “hole” Coal production • Coal production increased dramatically ever since the industrial revolution (1900-2000) • 7000 million tons of coals were made by the 21 century • Coal is mainly made of carbon (C)  burned with oxygen  carbon dioxide (greenhouse gas)  warms the atmosphere Metal Production • Steel and aluminum was mass produced in the 1950s to 1900, again exponential increase during the industrial revolution o Destroyed a lot of forests The Earth is Moved • The amount of earth moved by humans were close to none 5000 years ago • In the last 500 years, has been a peak upward slope to the present • Industrial revolution is the key to massive movement of earth by humans • Other than humans, waters move the earth fastest World-wide total consumption of resources: 60 x 10^9 tonnes/year Total mass of sediment transported to the sea: 16 x 10^9 tonnes/year  In the end, humans have moved the earth more than any other natural processes  Approximately 4 times more than the natural processes • Humans can’t produce and use earth materials without generating WASTE o Waste production has increased exponentially o E.g. CO2 in atmosphere Species lost each year • Number of species lost each year has increased dramatically as the industrial revolution took place, 1950s – 2000 • Species extinction rate risen Why has there been such a dramatic increase in the impact of humans on the earth system? • Population increase  More people  More usage of material  More impact • Technology development  more consumption of goods  More impact (e.g. Thomas midgely) To stop all this  Allenby calls for conscious, controlled actions  Think globally and act locally  everything you engineer/manage has an impact Lecture 4 – Chapter 1 (read pages 2-11 and 19 -27 ) Chapter 2 Earthquakes • To what end are humans engineering or should humans engineer, the earth? o Is moral one not technical one o We can do it but should we? And if yes to what extend towards what end? • The issue then is not whether we should begin earth system engineering because we have been doing it for a long time, albeit unintentionally. The issue is whether we will assume the ethical responsibility to do ESE rationally and responsibly • In managing earth system, there is an ethical dimension  you need to define your desired endpoints o Sustainability; create a system that can maintain itself in the future o Sustainable development; development that meets the needs of the present without compromising the ability of future generation to meet their own needs • It is not just about sustainability, equity matters o The wealth of the word’s 300 wealthiest individuals is equal to the combined annual incomes of 41% of the human population What is a suitable ethical framework for earth systems engineering? • Managing the earth requires: o Technical dimension o Ethical dimension o Economic dimension o Environmental dimension • All 4 combined  Risk Management o What risks are we willing to take for what benefits? o how to mitigate a geological hazard minimize damage and loss of life/injuries Scenario The government of Ontario proposes to build a nuclear reactor on the shore of lake Ontario near Kingston Our task Carry out risk analysis and risk management study, for the government, focused on seismic risk (Earthquake risk) Risk analysis and risk management  we carry this out in order to minimize damage from hazards, disasters, and catastrophes Hazard: something which might cause harm to people ( death/injury/property damage) • There are landslides on mars  is there a hazard from Martian landslides? o Yes we have human property on mars • There are both natural hazards and anthropogenic hazards ( human induced). o Both are often intertwined Resource: something that is useful to us • Water is a resource ( hydro electric power, we drink it, and etc) o But water as a hazard; drought and tsunami Lecture 5 – Hazards Continued • Hazard versus Resource, how do you decide what the damage threshold is? o Partly by empirical observations and scientific studies o Ultimately by societal “preferences” ( i.e. choices) • Consider “pollution” = hazard  very notion of pollution is culturally dependent o We define what is or is not “pollution” • Note also the consequences of synergy o Snow  can be hazard or resource o Wind  can be hazard or resource  Blizzard = snow + wind  hazard  Scenario: Geographic location with a fixed human population and infrastructure ( e.g. Kingston) o Imagine that we experience a hazard event o We go past the damage threshold o Flood event What are the three main factors that control the hazard “event” is? o Absolute amount (intensity)  way too much or way to little o Duration of the event  too long o Rate of change  too fast (not enough time to adjust to change) • Rate of change e.g. sudden impact of a large meteorite  can lead to mass extinction Burning, by humans, of oil coal + gas causing increase in CO2 in the Atmosphere may be leading to enhanced global warming • After a hazard event, there are both losses and gains o Some people lose and some people gain • When does a hazard even become a disaster or catastrophe? And what are the factors that decide that numbers of people are affected? Things like loss, injury, economic loss, media coverage, recovery, time. Geographic scale, size of region, how preventable it was should all be taken into consideration o Extent of human loss of life o Extent of human injury o Extent of money loss due to property damage o Group versus individual o Reconstruction time o Societal reaction o Geographic scale • Why is distinction of disaster and catastrophe important? o Governmental/world aid o Historical perspective  how often do really big event happen? • Truism in disasters o The poor lose their lives while the rich lose their money o 90% of the deaths are in the less industrialized countries o 75% of economic damage is in the more industrialized countires • How big a problem is a particular hazard? o How risky is it to be exposed to that hazard? o Risk: probability of hazard occurring x the severity of the consequences if the hazard happens o Ph x Sh = risk • How do we measure Ph and Sh? o Empirical observations and scientific studies o Social/economic impact studies Lecture – 6 & 7 Natural hazards: earth’s processes as hazards, disasters and catastrophies, second anadian edition with MyGeosciences place, 2/E, By Keller, biodgett & clague – textbook, purchase directly from www.mygeoscienceplace.ca or the book store • Should you believe the “experts”?  wise to add a margin of safety in risk analysis o Concept of safety factor ( estimate of probability of failure)  Experts have probably already added that margin of safety • How much risk are we willing to incur?  once you have the “data” (The determined values of Ph and Sh)  make your choice  it is entirely a matter of personal/ societal choice • People’s perception of risk o Tending to increase risk perception- volunatary hazard mountaineering  Direct impact ( earthquake)  Many fatalities per event o Tending to decrease risk perception  Indirect impact ( drought)  Few fatalities per even (car crash)  Common hazard (road accident) • E.g. case study of chlorinating water in peru o U.S.A studies showed that CL ( chlorine) in water elevates the incidence of bladder cancer • Fungibility o A person, and society needs to seek a prudent balance between the advantages of boldness and the advantages of caution o There are almost always opportunities foregone when we take precautions, and danger accepted when we do not • What is a life worth? Is this a question we should be asking? • Worth a life o To whom is the life important?  Individual person  Relatives  Company looking at employees  Government  Society as a whole • For society as a whole: a person’s worth to scoeity o Young vs old o Educated vs not educated o Present value vs future value o Rich vs poor • What is your life worth? Lets get out a calculator – read article o They use the value of a statistical life, placed at 8.16 million ( VSL ) o But is VSLY a better measure? • Genereic approach to risk analysis and risk management • Risk analysis o Understand the hazard o Determin the risk from that hazard for the region of interest o Risk = Ph x Sh • Risk management o Determine ways to reduce ph and sh o Do a cost – benefit analysis  determines what you can afford to do o Implement mitigation techniques if warranted Lecture 8 – no class Lecture 9 Generic approach to risk analysis and risk management Risk analysis 1- Understand the hazard (in general) 2- Determine the risk from that hazard for the region of interest o Risk = P x S H H 3- Determine ways to reduce P Hnd/or S H 4- Do a “Cost”-benefit analysis - Determines what you can “afford” to do 5- Implement mitigation techniques if warranted Ex. Nuclear plant building in Kingston, earthquake prone area 1- Understanding the hazard a) What causes earthquakes? b) Where do earthquakes occur? c) What energy do they release? o If not big, it doesn’t matter d) What exactly causes damage? San Francisco earthquake – Release of energy from the San Andreas Fault Elastic Rebound Theory: The rigid part of thte Earth can store elastic energy. When it breaks, the elastic energy is released - Ex. If you take a stick, it bends and strains – eleastic material BUT if you apply too much pressure, it will snap and break – stored energy is released Therefore earthquakes are associated with FAULTS – earthquakes happen when either: a. A fault forms b. There is an episode of movement on a pre-existing fault (movement on a fault that already is there.) Fault: A break/crack in rocks along which there has been appreciable displacement For a big earthquake, fault motion needs to be only a metre or so Strike-slip fault: Horizontal motion Dip-slip fault: Vertical or subvertical movement - Results in a fault SCARP - Two types 1- Normal dip-slip: ‘down the ramp’ 2- Reverse dip-slip: ‘up the ramp’ - How to tell is look at block sitting on the top and see which direction it goes - Check out pics in text Large earthquakes can be associated with any of the 3 fault types BUT the biggest are associated with reverse dip slip faults – think of two cars colliding Looking for faults - When friction, rocks btw broken and ground up and easily washed away - Features: o Valley o Rivers  And we often build major dams on such rivers because they make canyons Focus: The ‘point’ source of energy relase on the fault Epicentre: The point at the earth’s surface that is directly above the focus - Closest place at earths surface to the focus - Often receives the most damage b) and c) Where do earthquakes occur? What energy do they release? - Use seismometers o Detect the energy froma quake o Measure distance to an earthquake and thus locate it o Measure the energy released during an earthquake - How do they do this?? – next class Lecture 10 Assignment 1 Deadline –Sunday Seismometer – get background knowledge on this How do we find the focus of an earthquake  In other words how far away is the earth quake? o We first need to know what seismic waves are. And how they behave. o Body waves spread in all directions towards the surface of the earth Seismic waves • Seismic energy waves radiate out from the focus and earthquake as body waves • Some body wave motion ets transformed into surface wave motion when the body waves reach surface Surface waves • Love waves are at the right in straight forward direction • Rayleigh waves circle around • Surface waves generally cause most damage at surface • Rayleigh circular motion, love horizontal, slide to ride 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? What does the velocity depend on? The velocity of p and s waves depends on elasticity/density The more elastic a material is the higher the seismic velocity The more dense a material is, the lower the seismic velocity So in other words 1. The more elastic a material is the higher the seismic velocity 2. More dense a material is the lower the seismic velocity 3. So both P wave and S wave velocities change when they move into a different material V p = square root of (k +4/3 M) /P V s = square root of M/P P = density K and M = elastic moduli Measure of elasticity K= compressibility modules (stress needed to compress the material_ M= shear modules (stress needed to change shape ) Lecture 11 • P waves travel faster than S waves • Seismogram – first P wave then S wave and then the surface waves, relative to time for measurement • P stands for primary and S stands for secondary • Seismic velocities for rocks at earth’s surface o P waves ~ 5.6 km/second o S waves ~ 3.3 km/second • For an earthquake in Toronto ~ 250km from Kingston o How long until the first p wave reaches Kingston? ~ 1 minute o For a uniform earth it takes 6 minutes for s waves and 35 minutes for p waves to reach the other side on earth • To measure distance to an earthquake focus, we ues travel times  the time between the P and S wave arrivals at your seismometer • The longer the time gap between the flash of lightning and the peal of thunder, the farther away the storm is and this concept applies to the P and S waves too. • Earthquake waves cannot be measured accurately because its velocity under the surface which is initially not known, it needs to be calibrated to measure. • For Earth quakes, since we don’t know the seismic velocities at depth we needed to first create an empirical travel time graph • Known location and time, obtain the P-S arrival time differences from seismometers around the world • Velocity of P and S waves differ as they travel, therefore having a curve on a distance time graph • At what depth do earthquakes occur at?  at less than 700km depth • Radius of Earth distance from surface to center~ 6000 kilometres • 90% of earthquake foci are at depths of less than 100km • Radius of the earth is 6000 km • Why do earthquakes only occur in the outer 10% of the earth? • Only the outer part of the earth is rigid enough to experience brittle failure ( fault of formation) • Deeper in the earth, it is too plastic (or liquid) • How do we estimate energy released from a quake o Measure the intensity based on observed damage (eg. The mercalli scale o Modified mercalli scale of Earthquake intensity qualitative analysis o Subjective and varies with distance from epicenter Lecture 12 Charles Richter – wanted something more quantitative - The bigger the squiggles, the more energy is released - Measure the maximum amplitude on the seismogram Measure the Richter magnitude: a quantitative measure of energy released - Determined from the maximum s-wave amplitude on a seismogram (corrected for distance) - Measure the time between the first pwave arrival and swave arrival. Go to empirical travel time graph, and go where the time matches up to find the distance to epicenter. From there determine how big it actually was. Then avg them all Distance (km) Magnitude Amplitude Each integer on the scale represents an amplitude difference of 10 (logarithmic scale) - Magnitude 2 = 10 x Magnitude 1, Magnitude 3 = 10 x Magnitude 2 = 100 x Magnitude 1 - It is an open-ended scale (we don’t know how high it could go) 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 - Magnitude 5 to 8 earthquake? 30 x 30 x 30 = 27 000 The largest earthquakes ever recorded are ~9 on the richter scale Quakes <2.5 magnitude are not felt by humans What do the richter numbers mean in terms of actual energy release? - How would we figure this out? o Earthquake and underground explosion comparison September 11/01 generated earthquakes - Planes hitting buildings – 2 earthquakes - Buildings collapsing – 2 earthquakes Largest recorded earthquake: Chile 1960, Magnitude 9.5 How frequent are quakes? - Big earthquakes happen rarely - Lower magnitude quakes occur more often Power Law relationships – on a log-log plot, you get a straight line - Cannot predict earthquakes Magnitude Number per year <3 > 100 000 >3 > 30000 >6 100 >7 20 We will probably have one before this course is over What exactly causes damage? - Determine this by: a. Empirical observations b. Laboratory experiments c. Computer modeling In general: 1) The closer you are to the quake, the greater the damage 2) The greater the magnitude of the quake, the greater the damage BUT this is modified by natural and anthropogenic conditions o Natural: nature of soils/ rocks o Anthropogenic: nature of the structures that we buil List of earthquake hazards 1- Surface faulting: structures on the fault will be disrupted by the tearing motion o So don’t build right on active faults – but ppl do! Eg. San Francisco, and other parts of the San Andreas fault 2- Ground shaking: this is generally the greatest threat to buildings and ppl o In a big earthquake, the shaking can be severe even 100s of km away from the epicenter o Most ground-shaking damage is generally a direct consequence of SURFACE WAVES and if you are close to the epicenter , the p and s wave o The amount of shaking also depend on the nature of the soil/rocks in the area  Soft soils (eg clay) shake more than stiff soils (eg sand) which shake more than rock o Amplification is highest in water saturated sediment o Material amplification effect: When seismic waves slow down as they go into another material some of the energy is transferred into greater shaking o Ex 1985 mexico earthquake underwater near Acapoco  Acapulco wasn’t affected much but mexico city (100s of km away) was devasted  Mexico city built on mud o Aftershocks: Smaller earthquakes that occur soon after the main shock, with epicenters in the same area as the main shock  Can occur from minutes after to up to a year after  Aftershocks can cause collapse of already damaged buildings 3- Ground failure o Lecture 14 Mid term on feb 28 7:30 -9:00pm Tsunami causes Seafloor earthquakes Underwater earthquakes Collapse of the flank of a volcano into the sea Submarine volcanic explosion Impact of meteorite into the ocean Earthquake hazards  what exactly causes damage Tsunami in Lake Ontario = not very big  maximum of 2 meters Why? Because of shallow water depth Leads to only small amount of water displaced and speed of tsunami waves are low Fires • 1906 a.d. fire in san Francisco • Leads to disease because people cannot have access to clean water Human induced seismic hazards • Dam construction o Resovir goes down beside the dam and fault line is created at the bottom o Leading of earth by water changes the stress regime quakes can happen o Water infiltration below dam can lubricate faults  quakes can happen • Mining o The rocks will squzze into the newly opened space  due to the release of pressure Generic approach to risk analysis and risk management • Understand the hazard in general • Determine the risk from that hazard for the region of interest • Access seismic riks of an area o History of quakes in the past for that area o Human interaction/infrastructure • Assess seismic risk of area o Locate and determine nature faults in the area o Study history of earthquakes o Determine geologic geographic factors in the area o Determine human interactions with the potential hazard in the area o Look on the ground and fro the air ( and space ) but there can be hidden faults o Set up seismometers to help locate faults • Only effective for faults that have moved since seismometers were set up • Does every fault produce earthquake? No o Some are inactive, has not moved in last 2 million years o Some are potentially active, has moved in last 2 m.y. o Some are active has movevd in last 10000 years • Are these faults in the Kingston area? Yes all the way from small ones up to big ones Lecture 16 Midterm - thurs feb 28, 7:30-9:00 th - Make up on march 4 - Head TA: Tyler nash [email protected] Assess sismic risk of an area continued… 1. understand the hazard 2. determine the RISK form that hazard for the region of interest - Risk = P x S 2- Assess seismic risk of area a. Locate and determine nature of faults in the area b. Study history of earthquakes in the area - History of earthquakes in the area - Which faults are the most active? - What sort of energy is released by quakes? - Zones that are prone to earthquakes in Canada: - Arctic o Is this region high risk? -> NO because the popultiona is low - Western Canada - Eastern Canada - Steps to assess: 1. Set up seismometers - Gives an idea of which faults are most active - Gives some of idea of frequency and magnitude of quakes - Critical to collect as long a seismic record as possible 2. Determine RECURRENCE INTERVAL for BG earthquakes int the area (ie. How do big quakes happen?) – big means greater than magnitude 7 - How do we determine recurrence interval for big qukes a. Look at human historical records – they go back before seismometers b. Dig trenches and pits on active faults (study the faults themselves) - Identify ancient fault movements 14 - Use C dating method to bracket their ages (date old quakes) Aside: Relative time Law of Superposition: For sediment layers, oldest are are on the bottom, with the youngest on the top Youngest Oldest Law of cross-cutting relationships: Fault cuts across the layers therefore fault is younger than the layers Step 1: Determine the relative age of the fault Ex. Fault 1 is - younger than peat layer A but older than peat leayer B B A A Step 2: Peat layers contain dead organic matter. The time since the organic matter died can be determined by C method, so the absolute age of the faulting event can be bracketed BUT it is a “subjective” determination to decide if a particular movement event was a BIG earthquake or just a small one – we can turn to other evidence of big quake activity that is less subjective Continued from before… Determine RECURRENCE INTERVAL for BG earthquakes int the area (ie. How do big quakes happen?) – big means greater than magnitude 7 - How do we determine recurrence interval for big qukes a. Look at human historical records – they go back before seismometers b. Dig trenches and pits on active faults (study the faults themselves) - Identify ancient fault movements 14 - Use C dating method to bracket their ages (date old quakes) c. Look for evidence of ancient events - Ancient events: - Tsunami - Ground elevation and ground subsidence - These events can instantly bury swamps with sand -> You can date the dead organic matter (carbon 14 method) = This gives the
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