Complete GEOL 106 Notes.docx

17 Pages
81 Views
Unlock Document

Department
Geological Sciences and Geological Engineering
Course
GEOL 106
Professor
John Hanes
Semester
N/A

Description
 Economic cost of natural hazards is increasing due to population growth among other factors  Aral Sea – how humans alter the environment  Large lakes help to moderate climate  1969 – Armstrong lands on the moon  Powerful - humans see picture of the earth from outside  Scarcity, earth as a closed system, fragile  US laws on Environmental protection began in the early 1900’s. After the moon landing & Silent Spring (Rachel Carson) the number of laws took off with the environmental movement  “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” - David Rothenberg  “There are no passengers on spaceship earth. We are all crew members.” - Marshall McLuhan (Canadian philosopher of communication theory)  Earth no longer as big as we thought  View of earth from space increased our awareness of the fragility of the Earth and the need to better understand it. US President commissions a study of the Earth System to understand how to live in concert with this fragile Earth. [The result of the study is published on first handout]  An Example of earth system science  How earth’s parts and their interactions evolved. How they function today and how they might be expected to function in the future.  Earth system seen as a set of interacting systems; a change in one component/process can propagate through the entire system  Scale – time, size, distance.  Five “Reservoirs” or Subsystems of the Earth System [At first it was just 1,2,3 – Geology] 1. Atmosphere 3. Solid earth (rocks + soil) 5. Stars + Planets 2. Hydrosphere (water + ice) 4. Biota (life)  “Earth Systems Engineering: the World as Human Artifact” - Brad Allenby  The earth is increasingly a product of human engineering  Managing the Earth’s complex systems and their dynamics is the next great challenge for the engineering profession  The Earth, as it exists now is a human artifact – it reflects the historic, unconscious, and unintended design of a single species. Humans have always been conducting E.S.E and M.S.E.  Lead Contamination graph (in Greenland Snow)  Measurable during the Roman Empire but also as early as when humans first began burning forests for farmland  Increased with the beginning of the Industrial Revolution and grew exponentially with leaded gasoline (dropping of substantially with the birth of unleaded gasoline)  Example of the earth as “increasingly a product of human engineering”  How does past E.S.E. compare to future E.S.E.? 1. Scale – in the past the focus of scale was more local and less global 2. Intent –in the past regional & global effects were unintended & unanticipated  Thomas Midgely had more impact on the atmosphere than any other single organism in earth history. In 1921, he invented leaded gasoline. In 1930-1931 he invented Freon; the first of the chlorofluorocarbons (CFCs)  [graph] Coal production went from almost none in 1800 and grew exponentially to approx. 7,000M tones annul in the present day.  Coal (mostly carbon) burnt with oxygen produces CO – gr2enhouse gas (warms the atmosphere)  [graph] Metal production (Steel + Aluminum) has grown exponentially since the industrial revolution  [graph] Total amount of earth moved has grown exponentially since the industrial revolution. Both for farming (approx. 80Gt annually) and other metals and materials. i.e.: deforestation of the Amazon rainforest  Running water (rivers) moves the most amount of material of all natural processes.  However the total annual world-wide consumption of resources is 4 times greater than the total mass of sediment transported to the sea annually. Humans move slightly less than 4 times as much as all other natural processes.  Humans can’t produce and use Earth materials without generating waste. Our waste production has also increased exponentially (i.e.: CO in the atmosphere) 2  Waste production also affects species extinction rates. A new study found genetic obliteration increasing as a result of human activities. [graph] The number of species lost every year is increasing exponentially.  We can’t build large city skyscrapers without digging giant holes elsewhere on the Earth.  Why has there been such a dramatic increase in the impact of humans on the Earth System?  Partly due to population growth  Population is growing by 74M people annually or a city the size of San Francisco every three days  Advances in technological capabilities (i.e.: Thomas Midgely)  Conscious controlled management and engineering or earth systems – Allenby  i.e.: seeding hurricanes with dust to reduce its force  In the years that the Sahara Desert has greater dust storms, America has a less impactful hurricane season  “Think globally, act locally.” Everything has an impact  “To what end are humans engineering, or should engineer the Earth?” - Allenby  Ethical responsibility: a moral (not technical) question: Should we, to what extent, and to what end?  We need to define our desired endpoints. Where are we headed?  Sustainable development: meets the needs of the present without compromising the ability of the future generation to meet their own needs  Is sustainability enough?  How many individuals should we sustain?  What level of equity?  What level of material well-being is acceptable?  There is an unequal distribution of resources  United Nation Development Program: 300 wealthiest individuals have an income equal to 41% of the population  Martini glass world (see image)  Both sustainability and equity are needed when managing earth systems. Management requires 4 dimensions which collectively are called Environmental Risk Management:  Technical  Ethical  Economic  Environmental  Risk Analysis and Risk Management  Minimize damage and loss of life and injuries  mitigate [geological] hazards, disasters, and catastrophes  Hazard: something that might cause harm to people: death, injury, property damage  Landslides on mars are hazards – space rovers are human property  Hazards can be both natural and anthropogenic (human created or produced). Not black and white.  Resource: something that is of use to humans  Everything can be a resource or a hazard  “All substances are poison. There is none which is not a poison. The right dose differentiates a poison from a remedy.” - Paracelsus  Hydrogen sulfide (sewer gas) – acts as a relaxant of smooth muscle (vasodilator) and is deadly at high conc.  DDT – fights malaria, builds up in fatty organs of animals and humans  How do we decide what the damage threshold is?  Partially empirical observations and scientific studies  Ultimately determined by societal preferences  Human culture decides whether pollution (i.e.: cigarettes) is considered a hazard  Over time there may be changes in human tolerance or sensitivity to the hazard  Each factor on its own may be a resource. Together they may produce a hazard, disaster, etc.  i.e.: Blizzards – synergy of wind and snow  Three main factors that control how severe a hazard event is:  Absolute amount [Intensity]  Rate of change into hazard zone  Duration of event  After a hazard event there are losses and gains, winners and losers.  When does a hazard event become a disaster? A catastrophe? What factors decide this:  Geographic scale  Extent of loss of life, injury  Media coverage/public  Recovery time  Extent of economic loss perception/social reaction  Why is the distinction important?  Government, national, and world aid  Historical perspective: how often do the really big events happen?  Truism in disasters – the poor lose their lives while the rich lose their money  90% of deaths are in less industrialized countries  75% of economic damage is in more industrialized countries  How to determine that risk to humans from exposure to a particular hazard? [location dependent]  Risk = P x S  P – probability of hazard  S – severity of consequences H H H H  How do we measure P and H ? – eHpirical observations and scientific studies on economic/social impact  Should we believe the experts, or should we add a margin of safety in risk analysis?  The experts have probably already added a margin of safety.  i.e.: Experts advise ice be 8cm thick to support a person – probably less  Cost benefit analysis: what risks are we willing to take for what benefits; environmental, social, or economic  How much risk are we willing to incur? - It is entirely a matter of personal/societal choice. People's Perception of Risk Tend to INCREASE risk perception Tend to DECREASE risk perception involuntary hazard radioactive fallout voluntary hazard mountaineering immediate impact wildfire delayed impact direct impact earthquake indirect impact drought dreaded hazard cancer common hazard many fatalities per event airplane crash few fatalities per event road accident  US studied showed chlorinating water increases the incidence of bladder cancer. Peru removed chlorination from many wells. As a result 3500 people were saved from bladder cancer by an early death from cholera.  There are almost always opportunities forgone when we take precautions, and danger accepted when we don’t  “A person, and society, needs to seek a prudent balance between the advantages of boldness and the advantages of caution.” - Howard Margolis  What is the worth of a life and how do we go about determining its worth?  To whom is it important – relatives, company, government, society…  VSLY (yearly) – value  Worth to society – present vs. future value, education, age, economic status deteriorates with age.  The Value of Statistical Life (VSL) – worth 8.16 million at birth Chapter 1 Notes:  Magnitude-frequency concept: magnitude of hazardous event is inversely related to its frequency  Population growth, concentration of infrastructure, wealth in hazardous areas, and poor land use decisions are increasing our vulnerability to natural disasters  Impact also influenced by many factors, including climate, geology, vegetation, population and land use  Natural disasters are recurrent events - the study of past events provides needed information for risk reduction  Prediction of a hazardous event involves specifying the date and size of the event  A forecast is less precise and has uncertainty  Currently we deal with hazards primarily in reactive ways (after the disaster)  A proactive approach is required to anticipate and prepare for disasters  Disaster effects: many more people experience indirect effects than direct effects  Direct: death, injury, displacement, damage to property and infrastructure  Indirect: post disaster impacts, crop failure, starvation, emotional distress, loss of employment, reduction in tax revenues because of property loss, higher taxes to finance recovery  Stages of recovery following a disaster:  Emergency work  restoration of services and communication  reconstruction Lecture cont.  Generic Approach to Risk Analysis & Risk Management A. Risk Analysis i. Understand the hazard a. What causes the hazard? c. What range of energy do they release? b. Where do they occur? d. What exactly causes the damage? ii. Determine the region specific risk from that hazard (H x H ) B. Risk Management iii. Determine ways to reduce P Hnd S H iv. Do a cost-benefit analysis – determine what you can “afford” to do v. Implement mitigation techniques if warranted  Fault: a crack in the earth’s crust resulting from the displacement of one side with respect to the other  Earthquake: movement along a fault plane where stored energy is released (i.e.: San Andreas fault)  Elastic rebound theory: rocks on opposite sides of a fault are subjected to force and shift, they store elastic energy and slowly deform until their internal strength is exceeded. Sudden movement occurs along the fault, releasing the accumulated elastic energy, and the rocks snap back to their original undeformed shape.  Earthquakes can occur with the formation of a new fault or as a result of movement along a pre-existing fault  For a big earthquake the fault motion needs to be only 1-2 meters  Strike slip fault: horizontal motion  Dip-slip fault: sub vertical or vertical motion  Normal: down the ramp  Reverse: up the ramp  Biggest earthquakes are usually reverse dip-slip  i.e.: collision of two cars  Rivers often occupy faults/fault zones because the broken up rocks can be more easily washed away  We often build major dams on such rivers because the rivers carve canyons  Focus: the point source of energy release on the fault  Epicenter: the point at the earth’s surface that is directly above the focus  Damage will be greatest at the epicenter [in general] as it is the shortest distance from the focus  Understanding Earthquakes – Determining Seismic Risk  What causes earthquakes? – motion on faults  Where do earthquakes occur? What energy is released? – use seismometer  What causes the damage?  Seismometers allow us to:  Detect energy from an earthquake  Locate and measure distance to an earthquake  Measure the energy that is released  The most precise seismic stations use 3 seismometers  2 at 90⁰ for horizontal ground motion  Very expensive  1 for vertical ground motion  seismic wave behavior  Radiate out from the focus as body waves  Primary wave: compression & rarefaction, push-pull  Secondary wave: shear, up-down  transformed into surface wave motion at the surface  generally cause the most damage at the surface  Rayleigh wave: circular motion  Love wave: horizontal, side to side  Determining the velocity of seismic waves  [Elasticity of material] ÷ [Density of material]  Both P and S waves change in different materials but they will not have the same velocity in the same material:  Vp-wave= √[(k + 4/3 μ) ÷ ρ]  Vs-wave= √[μ ÷ ρ]  k and μ = elastic moduli ρ = density  for this reason p-waves are always faster  μ (shear modulus) – stress needed to change shape of the material  k (compressibility modulus) – stress needed to compress the material  At the surface P waves travel ~6km/second and S waves ~3km/second (P waves are about twice as fast)  To measure the distance to an earthquake focus we use travel times – time between P an S wave arrivals  Empirical travel-time graph - built because we did not know seismic velocities at depth  Records of P-S arrival time differences built up over time from earthquakes of known location  To locate an earthquake focus, 3 seismic stations are needed.  All earthquakes occur at <700km depth (outer 10% of the Earth) and 90% of foci are at depths <100km  Only the outer 10% is rigid enough (sufficiently elastic) to experience brittle failure (fault formation)  The rest of the earth is too plastic  How do we estimate the energy released from an earthquake?  Qualitative: measure the intensity, based on observed damage – Mercalli scale  Subjective  Varies with distance from the focus  Quantitative (Charles Richter – Richter Scale): measure max. amplitude of S wave to determine the amount of energy released corrected for distance  Each integer on the scale represents an amplitude difference of 10.  Open ended scale – we don’t know how high it goes (currently the largest recorded are 9-9.5)  Each magnitude integer step corresponds to about a 30 fold difference in energy release  What do Richter numbers mean in terms of actual energy released?  Compare to known explosions such as nuclear blasts  The collapse of the Twin Towers caused a magnitude of 2.3  Earthquakes of magnitude below 2.5 are not felt by humans  Largest recorded earthquake in Chile (1960) was magnitude 9.5, equivalent to the annual USA energy use  The bigger the earthquake the less frequently it occurs  Power law relationship: data plotted on a logarithmic-logarithmic graph results in a straight line relationship  Annually 20 earthquakes with magnitude greater than 7  Highly likely one will happen this semester  Can determine what exactly causes damage by: a. Empirical observations b. Lab experiments c. Computer modeling  Usually damage increases with proximity to the earthquake and with earthquakes of higher magnitudes  But this is modified by natural (nature of soil and rocks) and anthropogenic (nature of our structures) conditions List of earthquake Hazards 1. Surface faulting – structures on the fault will be disrupted by the tearing motion  Don’t build on active faults – but people do (i.e.: San Francisco) 2. Ground Shaking - this is generally the greatest threat to buildings and people  In a big earthquake, shaking can be severe 100’s of kilometers away from the epicenter  Most ground shaking is a direct consequence of surface wave motion.  However, at close proximity to the epicenter, P-wave and S-wave arrivals can also have an impact  The amount of shaking is also dependent on the soil composition of the area (i.e.: Loma Prieta earthquake 1989)  Material amplification effect: seismic waves slow down as they go into a new medium (material), causing some energy to be transferred into greater shaking (amplification increase)  Shaking in soft, water saturated soils (clays) > stiff soils (sand) > rock  After shocks: smaller earthquakes that occur soon after the main shock, with epicenters in a similar region  Can be from minutes up to a year after the main shock  Can cause collapse of already damaged buildings 3. Ground Failure a. “Landslides”  Hegben, Montana (1959)  Yungay, Peru (Mt. Huascaran 1970) b. Liquefaction of soils – sand or clay soil that changes strength when shaken to flow like a liquid  Saint-Jean-Vianney, Quebec (1971)  Magnitude 9.2 Alaska (1964)  Liquefaction of sand pushes sand up to the surface creating sand volcanoes 4. Tsunami - Japanese word for “harbor wale”, colloquial term is tidal wave (not related to tides)  seismic sea wave generated by an earthquake rupture in the seafloor pushing water up. Wave moves rapidly in the deep open ocean reaching speeds of 500-800km/h (speed of a passenger jet plane). As the wave nears land it slows to about 45km/h but it is squeezed upward, increasing to heights as much as 60m or more (18 stories).  Open ocean tsunami waves have wavelengths up to several 100km and a tiny amplitude ~1m.  Ordinary wind-produced waves have shorter wavelengths  Tsunamis in lakes will not be very big due to the shallow depth of the water  The water displaced in Lake Ontario would probably only create waves with a maximum height of 2m  Landslides into a lake can cause much larger tsunamis – lucky the land is not steep around Lake Ontario  Tsunami causes:  Seafloor earthquakes (Banda Aceh)  Underwater landslide (Lituya Bay Alaska , 1958 – 500m tall waves)  Collapse of the flank of a volcano into the sea  Submarine volcanic explosion (Krakatoa, India)  Impact of a meteorite into the ocean 5. Fires – 1906 fire in San Francisco 6. Disruption of water supplies often resulting in disease – Cholera in Haiti 7. Human induced seismic hazards  Dam Construction [and subsequent valley flooding]  Loading of the earth by water changes the stress regime and can trigger earthquakes  Water infiltration below the dam “lubricates” faults causing earthquakes – Malpasset Dam failure in Frejus, France (1959)  Pumping liquid waste down a fault  Denver Colorado Rocky Mountain Arsenal deep injection disposal well  Possible method of earthquake control through many small earthquakes  Mining – rocks squeeze into the newly opened space due to pressure release  Can result in sudden rock bursts  Pumping oil and gas from the ground  Detonating underground nuclear explosions  To continue our Risk Analysis we must look at region specific seismic risk  Locate and determine the nature of faults in the area of interest  What type? – the most dangerous being reverse dip slip  Look for clues on the ground, in the air and from space  But there can be hidden faults – set up seismometers to locate faults  Only effective for faults that have moved since seismometers were put in place  Fault zones are also very complex – the whole system is not moving in an identical direction  But not every fault produces an earthquake  Inactive faults – have not moved in the last 2 million years  Potentially active faults – have moved in past 2 million years  Active faults – have moved in the last 10,000 years  However we decide what is an appropriate risk (i.e.: 20,000 years)  Are there faults in the Kingston area? – Yes, even very big ones such as the St. Lawrence River Rift  Study the history of past earthquakes in the area – create the longest possible seismic record  Set up seismometers to determine which faults are most active  frequency and magnitude of earthquakes; how often do big earthquakes occur  3 zones are prone to earthquakes in Canada: Arctic, Western and Eastern  Note: the Artic zone is not high risk because of low population  Determine the Recurrence Interval for “big” earthquakes (magnitude >7) in the area 1. Look at human historical records (before seismometers) by digging trenches and pits on active faults  Law of Superposition: Oldest sediment layers are on the bottom, youngest on top  Law of Cross-Cutting Relationships: a fault that cuts across layers of rock in younger than the rocks  Carbon 14 dating method to bracket their ages – only works for about 60,000 years  Peat layers contain dead organic matter – time since death can determine the age of the fault  Determining size of earthquake is subjective 2. Look for evidence of ancient tsunamis and ground elevation/subsidence as these events can instantly burry swamps with sand  C dating of the dead organic matter will give the age of the earthquake  Los Angeles recurrence interval: in 1400 years, 9 major events; recurrence interval of 160 years 3. Construct probability and earthquake hazard maps to show earthquake prone areas  Determine the geologic/geographic factors – nature of soil/bedrock  Map out location of rocks, sand, clay soils, etc.  Map out cliffs and hills at risk of landslides  Map out zones of soils prone to liquefaction  Map out tsunami-hazard zones  Determine human and infrastructural interaction with the potential hazard  Distribution of the population in the area and the proximity of people to high risk zones  The nature of the human infrastructure  Proximity of buildings and roads to high risk zones  Building materials, and design of the infrastructure Chapter 2 & 3 Notes:  Triangulation: process by which an unknown focus is found using three known distances from known locations  Earthquake cycle – elastic strain drops abruptly after an earthquake and then slowly accumulates until the next  Strain: deformation of bedrock resulting from stress  Resonance: frequency of the shaking matches the natural vibrational frequency of the building  Slip rate: average displacement rate on the fault measured over thousands of years  Long-term slip rates of most major faults in North America are unknown or very poorly known  Earthquake forecast – probability of occurrence of a specified magnitude in an area within a specified time frame  Earthquake prediction – given magnitude will occur in a defined region in a restricted time frame (hours – weeks)  Microzonation: identification of areas subject to different earthquake hazards  Tsunami watch: a notification that an earthquake that could cause a tsunami has occurred  Tsunami warning: a tsunami has been detected and is moving across the ocean towards the area  In general it takes an earthquake of magnitude 7.5 or greater to generate a damaging tsunami  When the source of a tsunami is less than 100km away there is insufficient time to warn and safely evacuate people Risk Management III. Determine ways to reduce P (Part E) and S (Parts A-D) H H A. Apply land-use planning and zoning  Use high-risk areas for low population use (eg. parks, gold courses)  Use set-back locations to restrict building too close to the fault  Don’t build in areas of soft soil or soils that might liquefy B. Apply stringent building codes – to minimize damage  Increased initial cost to incur less damage cost a. Chose appropriate building materials  Good, flexible materials: wood, steel, reinforced concrete  I.e.: dry stone walls of Machu Picchu – stones not cemented and move freely  Bad, inflexible (rigid) materials: heavy masonry, stucco, adobe, unreinforced concrete  Loma Prieta and Armenia (1988/89) had earthquakes of similar magnitude (6.5-7) but 65 people were killed in the former and 50,000 in the latter – because of poor building materials b. Chose resistant building design  Period of vibration - worst damage occurs when ground and building period of vibrations are the same  i.e.: pumping your legs with the rhythm (period) of a swing to accelerate and decelerate  ground period of vibrations [composition] – soft soil; several seconds, solid rocks; <1 second  building period of vibrations [height] – tall; several seconds, short; 1 second  Simple geometry building plans are most resistant to earthquakes  Supports to resist seismic waves: bolts, brackets, braces, blocks, panels, and shock absorbent structures  Retrofit (strengthen) existing structures c. Legislate construction regulations C. Set up warning systems and emergency-response plans  earthquake and tsunami early warning systems - radio waves travel faster than seismic waves  Minimize Earthquake damage  Set up seismometer near faults to transmit warning signals to more distant cities  Provides a 15 second to 1 minute warning – enough time to shut off gas valves, stop trains, etc.  Minimize tsunami damage  Sensors on the ocean floor that detect sudden changes in ocean depth  Maintain natural shorelines – mangrove trees lessen impact of tsunami waves  Limit population centers along shoreline  Provide appropriate emergency equipment and personnel  Prepare emergency response plans as teamwork I critical in implementing emergency measures  Educate the public – information booklets, earthquake drills, etc. D. Predicting earthquakes  Long term – determine recurrence intervals and look for seismic gaps  Seismic gap – locations on the fault where there have not been recent earthquakes  Seismic gaps are high risk areas - stored energy is being built up  The fault is locked due to high frictional resistance (i.e.: San Francisco area)  Short term – nearly impossible to pin-point precise times of incoming earthquakes  Chaos Theory – earthquakes are a chaotic system, there is no trend or method of prediction  However, changes preceding an earthquake might provide some warning – precursors  Dilatancy: stress build up forms micro-cracks in the rocks  Opening of cracks causes an expansion in volume which can lead to:  Ground Bulge  Micro-seismicity and foreshocks E. “Controlling” earthquakes  Pump water down the fault to lubricate the faults – big risk, what if this triggers a big earthquake The Rock Cycle and the Plate Tectonic Cycle  Earthquakes are caused by fault movement due to stress on rocks in the Earth from the release of internal heat.  Energy acting on the earth  External energy – wears down the Earth’s surface (hydrologic cycle)  Internal energy – builds up the Earth’s surface (volcanoes)  Rock Cycle – the interaction of external and internal energy  Rocks are in constant change from one type to another  Igneous: formed when liquid magma cools and crystalizes  Sedimentary: formed when weathered particles get deposited and lithified  Metamorphic: formed when pre-existing rock is changed under high temperature and pressure in the solid state  The release of Internal Energy from the Earth – by conduction and convection  Conduction – bumping together of atoms  Convection – large scale movement of hot material [requires gravity]  Internal heat is not released uniformly over the Earth’s surface  there are discrete zones of higher heat release  80% of heat release reaching the surface comes through these zones at volcanoes, earthquake centers, and mountain belts  Zones revel the patterns of large scale convection in the mantle  Theory of Plate Tectonics  Outer 100km of the earth is like a cracked e
More Less

Related notes for GEOL 106

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit