GEOL 105 Risk Assessment Cost deaths damage x Probability of event High cost low probability Yellowstone Low cost high probability thunderstorm Katrina Sandy Japan 1245 deaths 108 billion damage 2 deaths 700 million 15 550 deaths 309 million Prediction What size event where when specific time Forecast What size event where probability of event long time window Hazard Natural event that could cause a problem Disaster 10 or more people are killed 100 people effected state of emergency Catastrophe massive disaster that requires significant amount of money and time to recover Recurrence Interval RI Avg length of time between events Date of last disaster date of earliest disaster of intervals between disasters Probability of an event 1 RI Risk Prob x cost Location and size RI and probability Estimate of cost of event and determine risk Hazard map Chapter 1 Rock Salt Halite All atoms placed at the corners of a cube Na placed on corners Cl placed on edges Rock aggregate of one or more minerals Granite quartz hornblende Most common minerals Quartz harder than glass strong mineral Feldspar as hard as glass difficult to break Weak Minerals Clay minerals silicate minerals formed by weathering of other minerals Calcite weathers easily limestone and marble Minerals summary elements consist of protons neutrons and electrons isotopes of and element have Types of Rocks Categorized by formation Igneous Rocks Formed when magma crystallizes Granite Sedimentary Rocks Rocks exposed at the earth s surface are weathered Sandstone May be Transported deposited buried compacted cemented Metamorphic Rock When rocks are buried deep below the earth s surface exposed to heat and pressure they transform without melting Go through a chemical reaction to change Slate Strength of rock is determined by how well they hold together when a force is applied Summary Rock is an aggregate of minerals 3 kinds of rocks Relative strength of granite sandstone shale Geologic Dating and the Geologic Time Scale Relative age dating sequence of events Absolute age dating actual date or number The principle of superposition younger rocks on top of older rocks The principle of original horizontality Sedimentary rocks are formed in flat layers The principle of cross cutting relationships geologic events that cut across existing rocks are younger Principles of relative age dating Superposition Original horizontality Lateral continuity Cross cutting relationships Principle of faunal fossil succession Fossil Succession Earth 4 5 BYO Certain fossils are always observed in the same sequence of sedimentary rocks Can be used to establish age equivalence between rocks in different areas Eons Cryptozoic Eon invisible life microscopic fossil Phanerozoic Eon visible life visible fossils Eras Paleozoic old life fish 542MY 251MY Mesozoic middle life reptiles birds early mammals flowering plants 251MY 65MY Cenozoic new life age of mammals 65MY Present Half life The time it takes for one half of a radioactive element to decay Original atom parent Decay product daughter Determining age of rock Determine amount of half lives Multiply by length of 1 HL Composition Crust 6 70km thick silicate minerals Plate Tectonics o Oceanic Crust thin and has more iron and magnesium o Continental crust thicker and has more aluminum and potassium Mantle Rocky silicate minerals more iron and magnesium Core iron o Outer core liquid o Inner Core Solid Rheology How a material behaves under pressure Cold outermost rigid layer Lithosphere Warm soft weak layer Asthenosphere Plate tectonics Lithosphere broken into plates Pieces move horizontally relative to each other 9 16 15 Plate Boundaries Convergent Plate Boundaries Plates move towards each other Divergent Plates separate Processes Subduction zone oceanic plate submerging under continental plate or oceanic plate Largest Earthquakes explosive volcanoes volcanic arcs oceanic trench Sea Floor Spreading Ocean Ocean Faulting in the plate boundaries magma fills in the Transform plates slide parallel to each other Cause of Plate movement and energy convection of magma under the surface cracks Small earthquakes many underwater volcanoes mid ocean ridges oceanic lithosphere forms Translations Big earthquakes no volcanoes Continental margin the zone of the ocean floor that separates the thin oceanic crust from thick continental crust 9 18 15 9 21 15 Continental Drift Alfred Wegener Continental Drift 1912 Wegener s Hypothesis German meteorologist and polar explorer Wrote The Origins of the Oceans and Continents in 1915 He proposed Continental Drift Pangaea Pieces of Evidence Jigsaw puzzle fit of continents Fossils Paleoclimate indicators Mountain Chain Terminations Criticisms of Wegener s Ideas Wegener had multiple lines of strong evidence He couldn t explain how or why the continents moved New evidence from the oceans revived his theory Development of the Theory Mid Ocean ridges A mountain range ran through every ocean Sea floor bathymetry using sonar to map the ocean floor Paleomagnetics Magnetic stripes Sea floor spreading Modern evidence from satellites GPS Focus The point of rupture below the surface Epicenter Point on surface above the focus What Causes Earthquakes Faults Normal Faults Divergent plate boundaries Thrust Faults Convergent plate boundaries Strike Slip Faults Transform Plate Boundaries 8 Hazards associated with Earthquakes 1 Building Collapse 2 Falling Debris 3 Highways and Structures collapse 4 Water and gas mains break fire 5 Landslides 6 Subsidence 7 Tsunami Seismic Waves Shockwaves that travel outward from the Earthquake focus 1 Body waves travel through the body of the planet a P Waves Fastest type of wave compressional wave can travel through all Seismic Waves mediums b S Wave 2nd fastest wave shear wave can only travel in solids c Surface Wave Slowest arrives last complicated motions only travels in solids 2 Surface waves Travel along the surface of the planet has the highest amplitude and lasts the longest time causes the most damage Measuring Earthquake Size Intensity Mercalli Intensity Scale What is felt by people and the effects Magnitude total amount of energy For each increase in Magnitude scale ground motion is multiplied by 10 Logarithmic scale 9 28 15 Earthquakes cont Foreshock A smaller earthquake that occurs before a larger main quake Aftershock Any ground movement after the earthquake Precursors No reliable precursors for earthquakes Inverse relationship between the size of an event and the