Midterm Exam Study Guide
Midterm Exam Study Guide GSC106
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This 15 page Study Guide was uploaded by Blythe Coward on Tuesday February 24, 2015. The Study Guide belongs to GSC106 at University of Miami taught by Dr. Terri Hood in Spring2015. Since its upload, it has received 92 views. For similar materials see Geological Influences on Society in Geology at University of Miami.
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Date Created: 02/24/15
GSC106 Study Guide Midterm 1 Solar System Inner Planets terrestrial planets Mercury 0 Venus Earth Mars Outer Planets gas giants Jupiter 0 Saturn Uranus Neptune Astronomical Unit 0 Distance from the earth to the sun 93 million miles 0 1AU1 astronomical unit Space Weather Sun s Corona Outermost layer of sun that is so hot that it shoots outa continuous stream of protons called the quotsolar windquot 0 Hard to see due to sun s brightness Solar Wind Speeds up as it moves away from the sun Mach 3 at Mercury to Mach 9 at Pluto Leaves corona at different speeds depending on sun s magnetic eld lines Sun s rotation gives the magnetic eld and solar wind its spiral form Coronal Mass Ejections CMEs Large powerful emissions of material in one direction 0 Move out from the sun in a given direction only some come towards us Interaction of earth s magnetic eld with auroras o Earth s magnetic eld de ects the majority of the solar wind coming towards us 0 Some charged particles get channeled towards the North and South poles Reactions with our atmospheric gases create 0 Northern Lights aurora borealis Southern Lights aurora australis Effects of CMEs 0 Push back protective envelope of Earth s magnetic eld 0 Auroras brighter extend farther from poles Satellite failure fries circuitry o Disrupt communication and navigation systems Overload power grids at higher altitudes Radiation hazard for astronauts quotErodequot ozone layer which protects us from UV radiation 0 Radiation exposure in passengerjets ying highlatitude routes Sunspot Cycles 0 Solar activity varies in 11 year cycles 0 More solar activity more dark spots on the sun 0 Time of highest solar activity solar max 0 Last solar max 20122013 Comets A small icy body that when passing the sun heats up and begins to outgas Shortperiod comets 0 Period less than 200 years 0 Come from the Kuiper Belt A ring of small icy bodies outside the orbit of Neptune 30100 au away 0 Forces throwing sp comets in towards the sun Collision with another Kuiper Belt object Gravitational pull of other planets especially Neptune Many are strongly in uenced by Jupiter s gravitational pull quotJupiter family cometsquot periods less than 20 years Longperiod comets 0 Period of over 200 years 0 Come from the Oort Cloud Sphere of icy material that extends halfway to the nearest star 20000100000 au away Stuff barely held by the sun s gravitational pull 0 Randomly orientated 50 retrograde going around the sun in opposite direction from rest of solar system 0 Period can be thousands to million of years Most found are new to science 510 big long period comets approach the sun each year 0 quotCreatedquot by perturbation of their orbits Movement of nearby stars and dust clouds O Shock waves from supernovas Gravitational quottidesquot in the Milky Way Galaxy Asteroids Small rocky bodies orbiting the sun 0 Come from the asteroid belt 0 Doughnutshaped ring of small bodies 0 23 au away between orbits of Mars and Jupiter 0 Thought to be material that never formed a planet Too small mass Gravitational pull ofJupiter Half are randomly distributed throughout the belt 0 Other half are found moving in quotfamiliesquotthought to be remnants of larger parent bodies broken into fragments by early collisions with other asteroids Effects ofJupiter o Asteroids are in resonance with Jupiter Over time Jupiter makes their orbit more eccentric pulls them out of the asteroid belt 0 Resonance Gaps Areas in the asteroid belt that correspond to 21 and 31 resonance with Jupiter are depleted in asteroids Main source of asteroids whose orbits travel through inner solar system Impact Craters Earth surface processes destroy or hide most terrestrial impact craters that have occurred over time o 1 Plate tectonics destroy crust at subduction zone 0 2 Erosion wears away craters o 3 Sedimentation covershides craters Simple craters 0 Small smooth bowl shape 0 Formation Initial impact vaporizes center of impact site most of projectile Large amount of material is lasted outward curtain of ejecta Transient shortlived deep crater becomes partially re lled with rubble impact breccia Complex craters 0 Larger craters caused by larger projectiles 0 Have a central peak or ring 5 caused by rebound of central area 0 Impact Diamonds 0 Tiny diamonds created by extreme pressure of impact Chances of Bolide Impact 0 The larger the meteoroidthe smaller the chances of impact 0 However the greater the damage 0 All meteoroids less than 30m in diameter burn up in the atmosphere Meteoroids 1m in diameter impact earth about once a year Meteoroids 10m in diameter 0 410 kiloton explosion 5x Hiroshima nuclear bomb 0 Impact once per decade 0 If hit in populated area would cause oca fatalities 0 Most occur over ocean or in remote areas Meteoroids 100m in diameter 0 Serious regional effects 0 Greater than 1 km objects 0 Drastic goba effects Physical effects 0 Impact crater Shock wave Megatsunamis Rain of aming ejecta 0 Regional to global res Climate effects 0 Short term weeksyears 0 Screening of sunlight by dust in atmosphere Impact winter darkness freezing temperatures 0 Long term decadescenturiespossiby millennia 0 Global warming drastic weather climate uctuations 0 Frequency 1 300000 to 1 million years gt100 Gigaton explosion gt100 miion megatons Human Approach to Bolide Threat Rationale for Identi cation Plan 0 The most important rst step is to identify and track potentially dangerous objects This would give us the most lead time in planning what to do when one is coming Spaceguard Survey quotAsteroid Hazard Mitigationquot 0 Changing the path to one that is not earth intersecting could be slowing it down or speeding it up 0 Methods of de ection 1 Surface burst nuclear detonation Could break asteroid into several large pieces 0 Increase threat rather than eliminating it 2 Stand off nuclear detonation 0 At some distance from target Asteroid might soak up energy like a sponge 3 Energy coupling nonnuclear method quotshovingquot Asteroidbased rockets 0 Lots of fuel required 4 Lasers nonnuclear method Groundbased or space based 5 Change object39s color quotPaint it Blackquot approach nudging nonnuclear method Absorbs more heatphotons emitted gradually affect orbit 6 Mass driver nudging nonnuclear method Electromagnetic conveyor belt planted on asteroid that hurls dirt from surface 7 Solar Sail nudging nonnuclear method Probably too low thrust 8 Solar concentrator Parabolic mirror that concentrates and focuses Sun s energy on asteroid surface 0 Plume of vaporized material Factors affecting optimal solution 0 Size 0 Composition comet stony or metallic asteroid Other physical properties one solid mass or rock pile Movement speed spin Intercept distancetime the most advance warning we have the more choices are available 0 No warning time no options 0 Warning time of less than 10 years probably nuclear attempts warning time for most longperiod comets less than 1 year 0 Warning time of more than 10 years many options including ones involving multiple quotvisitsquot Earth s interior 0 Inner Core solid 0 Outer Core liquid 0 Mantle Crust Convection in outer core Convection in the liquid iron outer core creates earth s magnetic eld 0 Protects living things on earth s surface from solar and cosmic radiation Convection occurs in mantle due to heat input from below 0 Causes ridged layer above mantle to break into plates that move relative to each other plate tectonics Plate Tectonics Divergent plate boundaries 0 Moving apart 0 Crust is being created 0 On map shown by 2 parallel lines Convergent plate boundaries 0 Coming together 0 Crust being destroyed o On map shown by line with triangles attached Tips of triangles point in direction subducting plate is plunging down quotteethquot are on overriding plate Transform plate boundaries 0 Moving past each other 0 Crust neither being created nor destroyed o On map shown by a single line Earthquakes o What is an earthquake 0 An episode of ground shaking o 1 Stress within the earth builds up over a period of time until it exceeds the strength of the rock 0 2 Rock fails by breaking along a fault 0 Fault o Fracture in earth s crust on which slip sliding occurs one side moves relative to the other Some are vertical but most slope at an angle fault plane Movement on most faults occur in discrete events when force trying to move 2 slides overcomes frictional resistance quotstickslip behavior Geography 0 Focus hypocenter Center of energy released during an earthquake Point at which initial rupture occurs 0 Epicenter Point on earth s surface directly above the focus Usually the place with most ground activity Seismic waves 0 1 Pwaves primary waves fastest o 2 Swaves secondary waves more slowly than the P waves 0 3 Surface waves travel only along ground surface not through body of earth Only can travel on the outer skin of the planet Seismograph o Instrument used to measure ground motion from an earthquake Use 3 of them 1 for vertical motion 2 for horizontal motion Triangulation of Epicenter Using SP arrival time lag Use arrival times of seismic waves unless you are at the epicenter order of arrival of seismic waves is Pwaves Swaves Surface waves 0 Time lag between arrival of the 3 sets of waves increases the farther you are from the epicenter Time delay between arrival of Pwaves and S waves can be used to calculate distance from epicenter 0 Using this distance at 3 different locations you can triangulate to locate earthquake epicenter Mercalli Intensity Scale and Richter Magnitude Scale 0 Two scales used to measure intensity Mercalli lntensity Scale 0 De nes intensity of an earthquake by the amount of damage it causes 0 Scale I to Xll 1 to 12 in Roman numerals o llsmallest felt by people 0 V wakes people things fall over 0 Xmany buildings destroyed Useful when reconstructing historical earthquakes 1886 earthquake in Charleston SC Richter Magnitude Scale Based on largest amount of ground motion takes into account distance from epicenter Is the logarithm of amplitude greatest motion in mm 10mm101 M1 100mm102 M2 1000mm103M3 So M5 is 10x stronger than M4 and M5 is 100x stronger than M3 Mlt2 not felt M6 moderate damage M89 absolute damage Rayleigh vs Love Surface Waves A Rayleigh waves pass by like ocean waves up and down motion B Love waves pass by like a snake lateral motion side to side 0 Types of Earthquake Damage 0 Damage due to ground motion Source of ground motion most earthquake motion is caused by surface waves Depends on How close you are to the epicenter Nature of substrate underlying ground 0 Least damage solid bedrock 0 Most damage loose sediments Building construction 0 Building to minimize earthquake damage 0 Landslides and Avalanches Ground on steep slopes gives way tumbles downhill o Sediment Liquefaction Shaking of sediment containing pore water water trapped between sediment grains unstable quotslurryquot Can create sand volcanoes sand erupts through overlying layers 0 Fires Fires spread from stoves lamps broken gas lines o Tsunamis Giant waves caused by Submarine fault Landslide Volcanic eruption Bolide impact in ocean Change in characterdeep water vs shallow water 0 In deep water wave height is very small less than 12m but is moving whole body of ocean o Waves travel very fast up to 800kmhr Tsunami carries a tremendous amount of energy Megatsunamis 0 Landslide and impact generated mega tsunamis can get 1020x bigger Dealing with Tsunamis o 1 Tsunami prediction 0 Seismographs record initiating earthquake which gives epicenter location amp earthquake magnitude 0 An oceanwide array of instruments detects passing tsunami whole ocean body motion gives speed 0 Tsunami warning issued Problem can t accurately predict runup maximum vertical height onshore above sea level without knowing amount sea oor was displaced 0 2 Minimizing Tsunami Damage 0 Identify tsunami runup areas 0 Evacuation plan 0 Avoid new development in highrisk areas 0 Design new construction to minimize damage Earthquakes at Different Plate Boundaries O o 1 Divergent boundaries Are all shallow focus lt70 km deep because molten mantle is rising towards surface Are less intense dangerous than earthquakes at other two types of plate boundary 0 2 Transform boundaries Shallow to deep focus up to 650 km below that mantle moves in a more plastic fashion Minor to major earthquakes Motion on transform faults is often distributed in a complicated fashion along a series of faults Stress of plate movement gets spread out father where sections of main fault are quotlockedquot stuck o 3 Convergent boundaries Most are subduction zones one plate plunging beneath other Earthquakes are shallow to deep focus lt650km and minor to major Strongest most destructive earthquakes occur along upper surface of subducting plate as it is forced beneath overriding plate Benioff zone f subducting plate is going under at a shallow angle then Benioff zone earthquakes get spread out laterally Ex West coast of South America f subducting plate s plunge angle is steep then you get a narrow zone of intense earthquake activity 0 Ex Japan Intraplate Earthquakes intrainside 1 Collision zones convergent boundary where 2 continental plates collideneither one goes down too buoyant compared to mantle 0 Ex Collision of Indian and Asian plates still occurring 0 Created the Himalayan Mountains 0 Severe fault zones extending into northern China 2 Ancient inactive fracture zones that remain weak 0 Many are failed rift valleys 0 Present day location of some major rivers 0 New Madrid Seismic zone Lies above an ancient failed rift valley 18111812 New Madrid EQ 5 quakes gt8 0 Changed course of Mississippi River Large sand volcanoes 0 Severe aftershocks for months 3 Extensions of midocean ridge fracture zones 0 Created as transform faults between segments of spreading ridges 0 Once formed remain as structurally weak zones 0 Big intraplate earthquakes are much less frequent than plate boundary ones 0 When they happen their effects usually extend much farther from epicenter Induced Earthquakes Earthquakes caused by human activities Most happen in areas that are already experiencing geological stress Usually due to o 1 Changing the quotstress eldquot of the area 0 2 Increasing pore pressure of water lubrication of locked faults 1 Reservoirs up to M65 Loading higher water pressure Epicenters located under the reservoir 0 Timing of earthquakes with high water levels 2 Withdrawal of oil or water 0 Changes stress eld often due to ground subsiding 3 Deep well injection Pumping uids deep into ground 0 Why 0 Oil recovery 0 Waste disposal 4 Rockbursts up to M4 Caused by mining activity 0 Sudden implosion of mine tunnel walls 0 Responsible for 50 of mining fatalities 5 Underground nuclear testing 0 Initial detonations up to M6 0 Also of concern are aftershocks and the creation of new faults Earthquake Prediction 0 Longer term 0 Identify seismic zones geographic clusters or belts of historical epicenters 0 Areas of particular risk Seismic gaps sections on an active fault which haven t moved for number of years Shorter term 0 Foreshocks Cluster of small earthquakes immediately preceding a large earthquake initiation of small ruptures Volcanoes Lava molten rock at earth s surface Magma molten rock below the surface Most volcanoes are on divergent or convergent plate boundaries 0 Divergent upwelling of mantle material 0 Convergent melting of subducting plate Hot Spots 0 Deep mantle source of molten material not associated with plate boundaries I Magma quotpunches throughquot plate moving above it o Volcanoes that form quothot spot tracksquot trace direction of plate motion relative to underlying deeper mantle Ex Hawaii Most volcanoes are on divergent or convergent plate boundaries 0 Divergent upwelling of mantle material 0 Convergent melting of subducting plate Products of Volcanic Eruptions o 1 Lava Flows Viscosity resistance to ow depends on composition of lava Magma Source mantle oceanic continent Increasing silica more resistance to ow 0 More volatiles more explosive behavior Hawaiian lava ows 0 Have different Hawaiian names depending on nature of ow 0 Pahoehoe Fluid ropy texture warm surface when moving Faster Ma c in composition low in silica Si02 0 Low in viscosity ow readily Rubbly blocky texture ow moves after surface has solidi ed which leads to break up into angular fragments Slower Ma c in composition low in silica Si02 0 Low in viscosity ow readily Intermediate composition flows More viscous Silicic high SiOz ows most viscous can plug volcano Ex Obsidian quotvolcanic glassquot quickly cooled sMcalava o 2 Pyroclastic Debris quotfire piecesquot Fragmented material thrown from a volcano which is solid by the time it lands Can form cinder cones a Smallest size volcanic ash Most of ash produced during volcanic eruptions is ejected upwards into the atmosphere Eventually falls out If ash makes it into the upper atmosphere stratosphere it can encircle the globe Larger eruptions put so much ash into the stratosphere that they partially block sunlight lowering global temperatures quotvolcanic winterquot Flying through volcanic ash can seriously damage or down jets Positivespectacular ash induced lightening Sometimes ash mixes with other material and moves in a very different manner 0 B Pyroclastic ow Ash mixes with air forms a superheated fastmoving avalanche o Aka Nuee Ardente French for quotglowing cloudquot 0 3 Lahar volcanic mud ow Ash and debris mix with water water often from snow melted by eruption Forms a slurry thick watery mixture Flow down valleys or river channels at speeds up to 50kmhr o 4 Jokulhlaup Icelandic Glacial outburst ood caused by volcanic eruption underneath glacier Typical sequence of events 0 Eruption melts huge volume of water 0 Water is initially trapped by surrounding ice topography 0 Water eventually nds its way out in a dramatic largescale event can be far from starting eruption 0 Places with large glaciers volcanoes Antarctica and Iceland Yellowstone quotsupervolcanoquot Current location of a continental hot spot that has been active for at least 16 million years Last eruption 600000 years ago ejected 240 cubic miles of debris Collapse of giant magma chamber created a 28x 47 mile of caldera almost half of Yellowstone National Park Ash deposits as far away as Missouri to northern Mexico Eruption Prediction Shortterm weeks to months prediction of impending eruptions is often possible because many volcanoes give off warning signals 1lncreased Heat Flow 0 Magma moving near surface can melt snowice sometimes trigger oods lahars 2 Change in weather 3 Earthquakes 0 Movement of magma up through country rock earthquakes o Earthquakes get stronger and closer to surface as magma rise weeks days before eruption 4 Gas and Steam Emission o Escaping from magma or heating up groundwater o Controlling Volcano Hazards 1 Risk assessment 0 De ne areas around volcano that lie on path of lava ows pyroclastic ows lahars River valleys that start on volcano slopes are particularly dangerous 2 Evacuation plan 3 Diverting ows 0 Flow channels Sakurajima Japansince 1955 has erupted 100200xyear o Freezing in place Heimay Iceland 1973 0 Positive aspects of volcano activity 1 Geothermal power 0 Clean nonpolluting source of energy that takes advantage of earth s internal heat o Is economically feasible only where the geothermal gradient increase in temperature with depth is high 0 A Can be pumped out and run through pipes to heat housesspas example Iceland 0 B As it rises hot groundwater decompresses amp turns 0 steam 0 Used to generate electricity with turbines 0 Ex Geysers geothermal eld N California supplies electricity to San Francisco 2 Formation of economically signi cant depos s Including precious metals and gemstones Creation of fertile soils 0 Weather of most volcanic rocks creates very fertile soils 0 Ex Indonesia volcanic island chain caused by subduction
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