GEOL 110 Study Guide
GEOL 110 Study Guide GEOL 110
Long Beach State
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This 20 page Study Guide was uploaded by Elizabeth Rubio on Wednesday February 10, 2016. The Study Guide belongs to GEOL 110 at California State University Long Beach taught by Klaus Hagedorn in Spring 2016. Since its upload, it has received 60 views.
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Date Created: 02/10/16
GEOL 110 2116 Lec. 3 (CHAPTER 1 CONTINUED) Observe precursor events Events that precede a hazardous event Example: earthquakes often precede volcanic eruptions Forecast or Predict event Forecast gives certainty of event Prediction will give an estimated time for events Warning the Public Involves statements to media and public at large DATA>SCIENTISTS>PREDICTION REVIEW GROUPPREDICTION>TO THE PUBLIC AND REGIONAL OFFICIALS Risk=(probability of event) x (consequences) Consequences : damages to people, property, economic, etc. Acceptable Risk Is the amount of risk that one or society is willing to take Frequent problem : lack of reliable data for either the probability or consequences Why is this important?> to evaluate the data whether or not the information should be passed on publically or not, depending on the specific event or risk. Hazards are link to each other: Some events may cause others Ex: Hurricanes and flooding Hazards linked to earth materials Ex: Some rock types are prone to landslides or liquefaction. Increases of number of people at risk More loss of life in highly populated compared to hazardous event in a less dense area Examples: Mexico City: 10,000 killed in 1985 with 8.0 earthquake Turkey: more than 17,000 killed from 1999 earthquakes World’s population has more than tripled in past 70 year. Population grows exponentially Increases exposure to hazards, increased pollution, reduced availability of food and clean drinking water, and a greater need for waste disposal and energy resources. Impact of hazards depend on: Magnitude: Amount of energy released Frequency: Interval between occurrences Other factors: climate, geology, vegetation, population, and land use Primarily reactive approach in dealing with hazards: Search and rescue Firefighting Providing emergency food, water,and shelter Need to increase efforts to anticipate disasters and their effects (planning) Landuse planning limitations Hazard resistant construction Hazard modification control Total losses are direct losses and losses related to human actions Effects from a disaster can be: Direct (felt by fewer people): people killed or dislocated, buildings damaged, etc Indirect (affect many more people): emotional distress, donation od money or goods, taxes for recover, etc. Recovery from disaster Emergency work Restoration of services and communication lines Reconstruction Options for avoiding and minimizing effects of disasters depends on: Perception of hazards Attitudes of people to be affected Awareness Anticipatory options include: Landuse planning Insurance Evacuation Disaster preparedness Artificial control There are some benefits for hazards Examples: Flooding provides nutrients for soil Landslides create dams to create lakes Volcanoes make new land and enrich soil Global climate change is likely to change the incidence of some natural hazards Sealevel rise increases coastal erosion Deserts and semiarid regions are likely to expand Warmer ocean water is likely to increase storm activity CHAPTER 2 California straddles the boundary between 2 tectonic plates San Andreas fault: Boundary between North American and Pacific plates Los Angeles and San Francisco located on opposite sides of the fault Movement of San Andreas fault in 1906 Caused this major earthquake Earthquakes not understood at the time Scientific investigations led to identification of fault and new understanding of earthquakes San Andreas fault system Many of moderate to large earthquakes in Los Angeles on this fault Mountain topography in coastal CA result of fault Earthquakes since 1906 have cost hundreds of lives and billions of dollars in property damage Future of the Fault Los Angeles and San Francisco. will be side by side in 20 million years May be a shift in the plate boundary and a change of topography 21016 Chapter 2.3 A detailed Look at Seafloor Spreading Midocean ridges discovered by Harry H Hess Evidence of seafloor spreading: 1. Identification and mapping of oceanic ridges 2. Dating of volcanic rocks on the floor of the ocean 3. Mapping of the paleomagnetic history of ocean basins Earth’s magnetic field is a NS or SN dipole Caused by convection in the outer core Magnetic field magnetized rocks, in which ironbearing minerals oriented themselves parallel to the magnetic field at the critical temperature known as Curie Point Paleomagnetism the study of magnetism Magnetic Reversal Volcanic rocks magnetism in opposite to today’s magnetic field. The magnetic field reverses every few thousand years. Cause is unknown. Geologists read from Magnetic anomalies: Seafloor < 200 mln y. Spreading at the midocean ridges explains stripe patterns, rising magma at ridge extrudes forming new rocks. Rocks magnetize (normally), new rocks push old rocks away and reversal of field is recorded Paleomagnetism (cont.) Magnetic Stripes Geologists use magnetometers to measure magnetic properties of rocks of ocean floor Mapping revealed striped ● “regular” and ”irregular” magnetic fields ● Parallel to ocean ridges ● Sequences of oceangoing strips matched with land Hawaiian Hot Spot Hot Spots: Volcanic centers deep in the mantle Hot materials moving up through the mantle and the crust Under continental/oceanic crust: Continental: Yellowstone National Park Oceanic: Hawaiian Emperor Chain Plates move over hot spots making a chain of island volcanoes Seamounts are submarine volcanoes 2.4 Pangea and present Continents Movement shaped and distributed continents ● 180 million years ago, Supercontinent Pangea broke up ● 50 million years ago, India crashed into China, creating the Himalayas Paleontological Evidence for Pangea Reconstruction of Pangea and recent continental drift clears up: Fossil data difficult to explain with separated continents Evidence of glaciation of several continents 2.5 How plate tectonics works: putting it together 2 possible driving mechanisms for plate tectonics Ridge push and slab pull Ridge push is a gravitational push away from crest of midocean ridges Slab pull ( which is more important) occurs when cool, dense oceanic plates sinks into the hotter, less dense asthenosphere Weight of the plate pulls the plate along Chapter 3 continued Depth of Focus Focus is the plate within the Earth where the earthquake starts Depth of earthquake influences the amount of shaking Deeper earthquakes cause less shaking at the surface Lose too much of the energy before reaching the surface Loss of energy is called attenuation Direction that the rupture moves along the fault influences the shaking Path of greatest rupture can intensify shaking Directivity Distance to Epicenter,seismograph Use difference between time first P and S waves arrive P waves with appear first Seismographs across globe record arrivals of waves to station site Distance to epicenter can be found by comparing travel times of the waves We need to know the distance due to the difference in velocity from the primary and the secondary waves Distance to Epicenter,seismograph (cont.) Location of epicenter At least 3 stations are needed to find exact epicenter Distances from epicenter to each station are used to draw circles representing possible locations The place where all 3 circles intersect is the epicenter ~This process is called triangulation Supershear Occurs when the propagation of rupture is faster than the velocity of shear waves or surface waves produced by the rupture Can make shock waves that make strong ground motion along the fault May significantly increase the damage from a large earthquake. 2816 2011 Tohoku Earthquake Japan located 200km (~124mi) West of Japan Trench ~Pacific plate subducts under Eurasian plate ~Frequent large earthquakes 3/11/2011 Strongest recorded earthquake in Japan (~70km away, 500 km section, moves down 4070km) Greater than expected ~Energy Released ~600 million times more than the Hiroshima bomb ~Well engineered buildings reduced the loss of life, tsunami wallfalse security (wave greater that 10m) Greatest loss of land and damage due to the tsunami 7.2 Earthquake detected two days before This was a size that was predicted to occur any day Didn’t expect it to be a foreshock to a larger earthquake Few buildings collapsed Allowed occupants to escape Widespread damage (superficial) and mina structural damage CHAPTER 3 People feel about 1 million earthquakes a year Few are noticed very far from the source Even less are major earthquakes Most earthquakes occur along plate boundaries TYPES OF FAULTS AND FAULTING Earthquakes occur along FAULTS Weakness in earth’s crust Places where rocks are broken and displaced Centuriesold mining terminology used Footwall ~Block below the fault plane ~Miner would stand here Hanging wall ~the block of rock that lies above an inclined fault or an ore body FaultingProcess of fault rupture Similar to sliding one rough board past another ~Slow motion due to friction ~Stresses the rocks along the fault ~Rocks rupture and displaced when the stress exceeds strength of rocks Stress Force that results from plate tectonic movements ~Tensional ~Compressional ~•Shearing Strain –Change in shape or location of the rocks due to the stress Types of Faults Distinguished by direction of rock displacement ~Normal dipslip ~Reverse dipslip ~Strikeslip DipSlip Vertical motion Normal or reverse: depends on movement of hanging wall StrikeSlip Crust moves in horizontal direction Blind faults do not extend to the surface because they are located under the surface We define faults either active or inactive faults Major problem with intraplate earthquakes generally lack of preparedness due to the occur less often Earthquake Cycle Change in strain ~Accumulation before an earthquake ~Drop after an event 3 or 4 Stages 1. Long period of inactivity 2. Accumulated elastic strain procedures small earthquakes 3. Foreshocks a. Hours or days before a large earthquake b. May not occur 4. Mainshock Major Earthquake Includes aftershocks: few minutes to a year after Epicenter Given by news reports Location on surface above the rupture Focus (hypocenter) Point of initial breaking or rupturing Displacement of rocks starts here ~Propagates up, down & laterally along the Fault plane ~Makes shock waves, called seismic waves Seismic Waves Caused by a release of energy from rupture of a fault Body Waves: Travel through the body of the earth P Waves, primary or compressional waves •Move fast with a push/pull motion •Can move through solid, liquid, and gas S waves, secondary or shear waves •Move slower with an up/down motion •Can travel only through solids Surface Waves: move along the Earth’s surface P and S Waves that reach the surface Travel more slowly than body waves Complex horizontal and vertical ground movement •Rolling motion •Responsible for most of the damage near epicenter –Love wave—horizontal ground shaking Tectonic Creep: Gradual movement such that earthquakes aren’t felt Can make slow earthquakes A.K.A. fault creep Can slowly damage roads, sidewalks, and building foundations Last days to months EARTHQUAKE SHAKING Shaking experience depends on: 1. Earthquake magnitude 2. Location in relation to epicenter 3. Local Soil and Rock conditions Strong shaking from moderate to higher magnitude Rickter Scale 1st magnitude estimates Recorded with a seismograph (seismometer) ~Measures maximum amount of ground shaking due to S wave Local magnitude ● Depends on where it’s located Both scales are logarithmic Based on powers of 10 Ground displacement for a magnitude 6 earthquake is 10 times that for the magnitude of 5. Both scales used in tandem –Reason magnitude may change after a quake •Richter: immediately following quake •Moment magnitude: days to months after –Magnitudes are approximately equal except for very large earthquakes •Therefore, size is simply M (magnitude) without designation of scale EARTHQUAKE INTENSITY Measured by Modified Mercalli Scale Qualitative scale (1XIII) based on damage to structures and people’s perceptions ~Can vary within an earthquake with a single magnitude ~Can vary from country to country • Modified Mercalli Intensity Maps –Show where the damage is most severe •Based on questionnaires sent to residents, newspaper articles, and reports from assessment teams •Recently, USGS has used the internet to help gather data more quickly Shake maps Use high quality seismograph data to show areas of intense shaking –Useful in crucial minutes after an earthquake •Show emergency personnel where the greatest damage likely occurred •Locate areas of possible damaged gas lines and other utilities GEOL 110 Natural Disasters 1252016 If there is inadequate weather conditions, this may be the cause for many natural disasters Earthquakecatastrophe 85% of people in PortauPrince lived in slum conditions Poor conditions lead to 190,000 destroyed or damaged homes ¼ million killed 2millions homeless with poor sanitation and poor water quality catastrophe was clear: heavy human development Land is prone to flooding and mass wasting Vegetation plays a role in our natural disasters topic Why is studying Natural Hazards are important? Experiences of large, costly, and deadly natural hazards since 1995call for investigation and mitigation Deadliest tsunami are caused by earthquake in the INDIAN OCEAN Tsunami in Japan caused by largest and costliest earthquake in history Catastrophic flooding in different areas of the world Volcanic eruptions that shut down international airports Worst tornado outbreak in the U.S.A history It is also important to investigate the causes: Physical, chemical, and biological ways in which events affect Earth’s surface Internal processes come from forces within the Earth Plate tectonics Result of internal energy of Earth External processes due to forces on Earth’s surface Atmospheric effects Energy from the sun What happens when tectonic plates move? They break, deform, Due to plate movements, new rocks form, and other rocks become magma or recycled. This involves the tectonic cycle What powers the process of the cycle/movements of the tectonic plates? Inner energy source in the geosphere. Hazard Natural process or event that is a potential threat to a human life/ property Disaster Hazardous event that occurs over a limited time period in a defined area Criteria (of natural disaster) 1. 10 or more people killed 2. 100 or more people affected 3. State of Emergency is declared 4. International assistance is requested (All should meet the criteria to be a disaster) Catastrophe (is a hazard at this time) Massive disaster that requires significant amount of money or time to recover Why is it a hazard? People are affected, massive amount of damage caused and so much money needs to be invested. Examples: Floods, snowstorms, tornados (center U.S.) etc. During that past half century, there has been a dramatic increase in natural disasters: ex: Haitian earthquake, Indonesian tsunami, Hurricane Katrina United Nation: 1990’s “International Decade for Natural Hazards Reduction” Mitigation ~it reduces the effects of something ~natural disaster preparation (information if there is a natural disasters ahead, we can inform the public to be aware or evacuate to safety) Note: Global Warming impacts an increase of natural disasters like wildfires due to increase of temperature. Effects of hazards can differ and change with time due to changes of patterns of human land use Human land use examples includes building schools or houses in areas, and people must be aware if there is or going to be any hazards within that surrounding for the public’s safety. Natural Hazards that cause the greatest loss in human life may not cause the most property damage Hazards vary greatly in their ability to cause catastrophe. Natural Hazards are repetitive (uniformitarianism) History or an area gives clues to potential hazards maps, historical accounts, climate, and weather data rock types, faults, folds, soil composition Geology conditions govern the type, location and intensity of natural processes Collectively, processes are called the geologic cycle 4 SUBCYCLES: ● Tectonic Cycle ● Rock Cycle ● Hydrologic Cycle ● Biogeochemical Cycle CHAPTER 2 Internal processes have incredibly important impacts of the surface of the Earth Responsible for continents and ocean basins Ocean’s currents and distribution of heat carried by seawater controlled by configuration of continents and ocean basins Responsible for regional landforms Earth is layered and dynamic Internal structure of Earth: ~By composition and density ~By Physical properties The outer structure of the Earth is the Crust. The Mantle is the inner core that in beneath the crust, which is a high density rock. It is composed with Magnesium and more. Earth’s Structure Inner Core ~Solid ~1,300km (808 mi.) in thickness ~High Temperature ~Composed of iron (90% by weight ) Lithosphere Cool, strong outermost layer of Earth Crust embedded on top Asthenosphere Below lithosphere Hot, slowly flowing layer of weak rock Continents VS. Ocean Basins Ocean crust is less dense and thinner Ocean crust is young (< 200millions years old) Convection Earth’s internal heat causes magma to heat up and become less dense Less dense magma rises Cool magma falls back downward Similar to a LAVA LAMP Why is convection similar to a lava lamp ?: Because the less dense magma rises when it is in the bottom or closer to the heat source Largescale geologic processes that deform Earth’s lithosphere Produce landforms like ocean basins, continents, and mountains Processes are Driven by forces within Earth. Lithosphere is broken into pieces Lithospheric plates or tectonic plates Plate Tectonics Plates move relative to one another Plates are created and destroyed Boundaries between lithospheric plates are geologically active areas Responsible for many of the most devastating natural hazard, like earthquakes and volcanoes. Seafloor Spreading Explained mechanism for plate tectonics At midocean ridges new crust is added to edges of lithospheric plates ~Continents are carried along plates Crust is destroyed along other plate edges ~Subduction zones Earth remains constant, never growing or shrinking Sinking plates generate volcanoes and earthquakes Sinking ocean plates are wet and cold Plates come in contact with how asthenosphere Plates melt to generate magma Magma rises to make volcanoes ~Volcanic arcs Earthquakes occur along the path of the descending plate ~WadatiBenioff zones Plate tectonics is unifying theory Explains a variety of phenomena ~Evolutionary change ~How the Earth works ~Direction of plate movement ~Similarities among fossils ~Changes in Earth’s magnetism Convection is likely drives plate tectonics 1.) In which of the following faults does the hangingwall move down relative to the footwall? A. Leftlateral strikeslip fault B. Rightlateral strikeslip fault C. Normal dipslip fault D. Blind fault 2.Which stage of the earthquake cycle may occur only hours or days prior to the next stage earthquake but may not always occur? A. Accumulation of elastic strain B. Mainshock C. Aftershock D. Foreshock E. Fault Slip 3. ) When reporting to the public where earthquake originated, new reports give the location of the A. Focus B. Hypocenter C. epicenter D. fault E. aftershocks 4.)Which is NOT a type of seismic wave? A. P wave B. Love wave C. S wave D. Ground wave E. Surface wave 5.) Which statements is false about P Wave? A. P waves cause the most of the damage of the epicenter B. P waves are the fastest of the waves C. P waves can move through solids, liquids, or gasses D. P waves move with a push/pull motion E. All of the above statements about P wave are true 6.) In which situation would you expect to experience the most shaking from an earthquake? A. Located 1 mile from epicenter, on hard igneous rock, not on the path of the greatest rupture M 4.5 B. Located 4 miles from epicenter, on mud, not on the path of the greatest rupture M 6.5 C. Located 3.5 miles from epicenter, on hard igneous rock, on the path of the greatest rupture M 6.5 D. Located 4 miles from epicenter, on mud, on the path of the greatest rupture M 3.5 7.) The most appropriate scale to use to compare earthquakes globally is the A. Richter scale B. Mercalli intensity scale C. monument magnitude scale D. attenuation scale E. Fujita Scale 8.) How is the intensity for an area determined on the modified Mercalli Intensity scale? A. People’s perception of shaking and extent of damage B. Measurement through seismographs C. Distance from the epicenter D. Amplitude of the waves E. Derived from the Richer scale value 9.) To determine the epicenter of the earthquake, scientists A. Locate the area where the most damage is centered B. Determine where the highest magnitude was recorded C. Measure where the wave frequencies were the greatest D. Find the intersection P and S arrival time data from three seismographs at different locations E. Find the strongest relationship between ground shaking and magnitude 10.) The greatest earthquakes with magnitude over 9 are usually associated with A. Transform faults B. Bling faults C. Subduction zones D. Divergent zones E. Interplate earthquakes 11.) What’s the major problem with interplate earthquakes? A. They generally result in the highest magnitude of earthquakes B. There is generally a lack of preparedness because they occur less often C. They occur more often than any other type of earthquakes D. They are events called megathrust earthquakes E. There are no interplate earthquakes; they only occur at plate boundaries 12.) What isn’t a secondary effect of earthquakes? A. tsunamis B. ground liquefaction C. landslides D. disease E. ground shaking 13.)What is NOT a natural service function of earthquakes? A. Exposure of economically valuable mineral resources B. Create scenic landforms C. Help prevent future larger earthquakes D. Destroy natural underground dams that slow or redirect flows E. Create preferential paths for surface water flow 14.)Human Activity can cause earthquakes through at these ways except: A. Underground testing of nuclear weapons B. Building over fault lines C. Injecting fluid lines D. Building dams E. Disposal of chemical weapon waste into Earth
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