GCS 106 Class Notes
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Date Created: 02/24/15
Rocks ForJocks Class Notes Class 1 Our solar system 0 Sun 0 8 planets Smaller chuncks of material asteroids spac chunks space dust Moving out from the sun 0 Inner terrestrial planets 0 Mercury 0 Venus o Ea h 0 Mars Outer quotgas giantquot planets o Jupiter 0 Saturn 0 Uranus o Neptune The 4 inner planets are very close to the sun compared to the outer 4 1 AU 1 astronomical unit distance from the earth to the sun is 93 million miles Scale and Relative Sizes 0 Moon vs Earth 0 Diameter of Earth New York to California 0 Earth vs Jupiter 0 Earth would t inside Jupiter s quotGreat Red Spotquot Jupiter is 2x as big as all the rest of the planters moon smaller stuff combined Jupiter vs Sun 0 Jupiter would t inside a large sunspot Class 2 Extraterrestrial Threats Space weather o Outermost layer of the sun corona is so hot that it shoots out a continuous stream od protons called the quotsolar wind Solar wind speeds up as it moves away from the sun 0 Solar wind leaves corona at different speeds depending on sun s magnetic eld lines Sun s rotation gives its magnetic eld and solar wind a spiral form Besides solar wind sun s corona sends out CME is very large powerful fast ejections of material 0 Move out from the sun in a given direction only some come toward us 0 How does the Earth system respond to all of this solar activity Earth s magnetic eld de ects the majority of the solar wind coming toward us Some charged particles get channeled toward the North and South poles Reactions with our atmospheric gases 0 quotNorthern Lightsquot Aurora Borealiss 0 quotSouthern Lightsquot Aurora Australis 0 Effects of CME s push back protective envelope of Earth s magnetic field 1 Auroras brighter extend farther from poles 2 Satellite failure fries circuitry 3 Disrupt communication and navigation systems 4 Overload power grids at higher latitudes 5 Radiation hazard for astronauts 6 quotErodequot ozone layer which protects us from UV radiation 7 Radiation exposure in passengerjets ight high latitudes route 0 Solar activity varies in about 11 year cycles are called Sunspot Cycles More solar activity means more dark spots on the sun Times of highest solar activity solar max 0 Last solar max was 20122013 Bolide impacts comets asteroids Class 3 Friday Class 4 Wednesday MLK Day Monday Class 5 Friday 0 Watched Armageddon Destruction of Earth 0 100000 objects greater than 1km in diameter 0 12 gt 250 km 0 largest ceres 1000 km size of Texas 0 Ceres layers Thin dusty outer crust Waterice Asteroids O O O O 0 Half are randomly distributed through belt The other half are found moving in families thought to be remnants of larger parent bodies broken into fragments by earthly collisions with other asteroids Angle that orbit is away from orbits of planets ecliptic plane Gravitational pull ofJupiter can alter asteroids orbits Doesn t for most asteroids because there is no relationship between their orbital periods Randomdirection quottugsquot that cancel each other out At particular distances from the sun within the asteroid belt asteroids go around the sun exactly 2x or 3x for every 1x forJupiter always get tugged the same direction These asteroids are in resonance with Jupiter Over time Jupiter makes their orbit more eccentric pulls them out of the asteroid belt Resonance Gaps O O The areas in the asteroid belt that correspond to 21 and 31 resonance with Jupiter are depletedin asteroids quotresonance gapsquot Main source of asteroids who orbits travel through the solar system 0 Impact craters O O O OO 0 All major bodies in the solar system have been subjected to large impacts resulting in crater formation Some have preserved a record of bombardment eg Earth s moon Earth surface processes destroy or hide most terrestrial impact craters that have occurred over time 1 Plate tectonics destroys crust are a subduction zone 2 Erosion wears away craters 3 Sedimentation covershide craters Still there are more than 160 known terrestrial impact craters Most ID d since 1950 New ones found 1 per month Impact craters are divided into 2 main groups depending on structure simple and complex Simple craters are smaller and have a smooth bowl shape 0 Formation of simple craters 0 Initial impact vaporizes center of impact site and most of projectile O O O O O O O O 0 Large amount of material is blasted outward curtain of ejecta Transient shortlived deep crater becomes partially re lled with rubble impact breccia o Meteor Crater Barringer Craterquot in Arizona is a simple Crater 34 mile across ironnickel asteroid 50 yards in diameter traveling 24000 mph struck 50000 yrs ago 0 Complex Craters Larger craters caused by larger projectiles Have a central peak or rings caused by rebound of central area Gosses Bluff Australia ring hills 3 miles wide Mjolnir Thor s Hammer crater 24 miles Chesapeake Bay Crater Complex crater 50 miles across Happened 35 million years ago covered by later sediments Caused impact of an asteroid 23 Miles across traveling mph most of creater lled with impact breccia blast wave incinerated all higher life forms within 600 miles of impact site Impactgenerated sunami 12 mile high struck all along eastern coast NC to NJ 0 2 other impacts 0 Impact Diamonds 0 Tiny diamonds created by extreme pressure of impact 0 Norlingen Germany Class 6 Monday Build inside an impact crater Cathedral in center made from local impact breccia Estimated to contain 25000 carats of tiny impact diamonds What are the chances of impact and how bad would it actually be 0 Depends on the size of the meteor o The larger the meteoroid the smaller the chances of impacts because there are fewer of them 0 What do these frequency numbers actually mean 0 Not periodicity predictable repeating pattern 0 Frequency is average per unit time when you take a long time period into account 0 11000 means Average 1 every 1000 years Chances in any given year are about 1 in 1000 1 o All meteoroids less than 3 m 1 ft diameter burn up in the atmosphere Ones slightly larger 5m hit earth s surface a couple times a year 0 Only small scale damage within a couple meters 0 One woman struck by meteorite in home in Alabama 1954 Objects 1 meter diameter impact earth about once a year Ones making it to Earth s surface create a crater 10 m across 0 Many explode in upper atmosphere 1 kiloton explosion 1000 tons TNT most tactical nuclear weapons 13 kilotons Largest danger from this size impactor is that it might be mistaken for a nuclear strike 0 10 meter 30 ft bolide 0 510 kton explosion 5x Hiroshima nuclear bomb 0 impact once per decade 0 if hit in populated area would cause local fatalities 0 most occur over ocean or in remote areas eg SikhoteAlin meteorite February 12 1947 in 0 Most recent 100 m 1908 Tunguska event 0 100 m bolide exploded in atmosphere ca 6 km above a remote area of Siberia 0 Central area of devastation Tunguska River 2 hours later would have hit St Petersburg 0 Only witnessed by remote tribes of Evenki nomads 0 1st scienti c investigation 20 years later 0 Radius of Burned area 25 km Felled Forest 120 km Visible blast effects Explosion heard 0 Most recent nearmiss 0 June 2002 a 100 m asteroid 2002 MN passed between the Earth and moon and was only discovered 3 days later Class 7 Wednesday 0 Impact of any bolide greater than 1 km has global effects 0 Physical effects lmpact crater Shock wave Megatunamis tsunamis w initial wave heights up to 12 km quotRainquot of aming ejecta l regional global res 0 Climate effects Short term weeks years 0 Screening of sunlight by dust in atmosphere l quotimpact Winterquot of darkness freezing temperature etc Long term decades centuries possibly millennia Global warming drastic weatherclimate uctuation 0 Frequency of 1km impacts 1 per 300000 1 million years gt 100 Gigaton explosion gt100 million megatons 0 September 2004 asteroid Toutatis 5 x 2 x 2 km passed within 0007 AU of Earth only 4x Earthmoon distance Was known have been tracking Toutatis since 1986 It was the closest approach for any known large asteroid or comet between now and 2060 o What are we doing about the threat of a big bolide impact 0 Rationale the most important rst step is to identify and track potentially dangerous objects would give us the most lead time in planning what to do when one is coming 0 Greater than 1km diameter has global effects First focus identifying all NEO s Near Earth Objects gt 1k diameter 0 NEA Near Earth Asteroid NEONEA closest distance to sun lt 13 AU One of most concern are those with earthcrossing orbits PHA s Potentially Hazardous Asteroids o Orbit comes within 120 AU of the Earth s orbit o 100 m diameter or bigger o Spacegaurd Survey Objective nd 90 of all NEA s gt 1 km by 2009 Status estimated to be 800 200 and as of October 2008 982 were identi ed In the process of looking for the biggest ones we are nding many smaller ones as well Next phase lDing NEA s gt 100m is underway What couldwould we do when an upcoming impact event is predicted o Asteroid Hazard Mitigation changing path to one that is not earthintersecting could just be slowing it down or speeding it up 0 Possible methods of de ection 1 2 CD Surface burst nuclear detonation Could break asteroid into several pieces is an increased threat rather than eliminating it Standoff nuclear detonation 0 At some distance from target Asteroid might soak up energy like a sponge Asteroidbased rockets Lots of fuel required Lasers Groundbased or spacebased Change object s color 0 quotPaint it blackquot approach so that it absorbs more heat so photons emitted gradually affect orbit Mass Driver Electromagnetic conveyor belt planted on asteroid that hurls dirt from surface Solar Sail Solar Concentrator Parabolic mirror that concentrates and focuses Sun s energy on asteroid surface gives off a plume of vaporized material 0 Some factors affecting optimal solution Size Composition comet stony or metallic asteroid Other physical properties one solid mass or rock pile Move Intercept distancetime the more advanced warning we have the more choices are available 0 No warning time no options 0 Warning time less than 10 years probably nuclear option 0 Warning time more than 10 years many oonns Class 8 Friday Effects of plate tectonics Earth s interior 0 Early segregation of earth denser material moved to center lighter to outside Temperature and pressure increase as you move from Earth s surface to its center Center 7000 degrees F 14 million atmospheres Earth made of concentric layers Layers Crust solid Mantle semiplastic Core outer lnner solid Important aspects of Earth s layers 1 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 2 Convection occurs in mantle due to heat input from below 0 Causes rigid layer above mantle to break into plates that move relative to each other plate tectonics o Earth s crust consists of 20 major plates plus many microplates All moving relative to each other Types of relative motion at plate boundaries 0 Divergent moving apart crust being created Convergent coming together crust being subducted and destroyed o Transform moving past each other crust neither created nor destroyed Earthquakes O 0 An episode of ground shaking The motion produced when stress within the Earth builds up over a period of time until it exceeds the strength of rock and rock fails by breaking along a fault Fault Fracture in Earth s crust on which slipsliding occurs one side moves relative to other Some are vertical but most slope at an angle Movement on most faults occurs in discrete events when force trying to move 2 sides overcomes frictional resistance Focus hypocenter Center of energy release during an earthquake Point at which initial rupture occurs o Epicenter Point on Earth s surface directly above the focus ls usually the place with most ground motion 0 Seismic Waves Earthquake occurs due to sudden movement on a fault Creates sudden pushpull felt by rock sends shock out from focus Travel very quickly 10002000x speed of sound 3 types 0 1 P waves Primary waves fastest 2 S waves Secondary waves 0 3 Surface waves travel only along ground surface not through body of earth slowest 0 Measuring Earthquakes Seismograph instrument used to measure ground motion from an earthquake Use 3 1 for vertical motion 2 for horizontal motion at right angles 0 Locating an earthquake epicenter Use arrival times of seismic waves unless you are at the epicenter order of arrival of seismic waves is o 1 P wave 0 2 S wave 0 3 Surface wave Time lag between arrival of the 3 sets of waves increases the further you are from the epicenter Time between P wave and S wave Using this distance at 3 different locations you can triangulate to locate earthquake epicenter o Homework If the end is near do you want to know Class 9 Monday 0 Using this distance at 3 different locations you can triangulate to locate earthquake epicenter o Earthquakes how big o Mercalli lntensity Scale De nes intensity of an earthquake by the amount of damage it causes Scale I Xll II smallest felt by people 0 V wakes people things fall over 0 X many buildings completely destroyed Useful when reconstructing historical earthquakes 0 Ex 1886 earthquake in Charleston SC Based on largest amount of ground motion Takes into account distance from epicenter o Richter Magnitude Scale Based on largest amount of ground motion takes into account distance from epicenter Is the logarithm of amplitude 0 10mm 10quot1 M 1 0 100 mm 10quot2 M 2 o 1000 mm 10quot3 M 3 0 So M 5 is 10x stronger than M 4 M5 is 100x stronger than M3 Scales o M lt 2 is not felt M 6 is a moderate amount of damage 0 M 89 is absolute damage There are many more small magnitude earthquakes than large ones 0 Plate boundaries on maps 0 Divergent boundaries Plates moving apart crust being created quotspreading ridgesquot Shown on maps by 2 parallel lines o Transform boundaries Plates moving past each other quotConnect other boundary types Shown on maps by a single line 2 spreading ridges connected by a transform fault o Convergent boundaries Plates coming together Usually one plate overrides the other Other plate that is being forced back down into the mantle is being subducted Shown on maps by line with triangles attached Tips of triangles point in direction subducting pate is plunging down quotteethquot are on overriding plate Class 10 Wednesday 0 Types of Earthquake damage 0 Damage due to ground motion depends on How close you are to epicenter Nature of substrate underlying ground 0 Least damage solid bedrock Most damage loose sediments Building construction 0 Building to minimize earthquake damage 0 quotBase isolatorsquot Te Papa museum in Wellington New Zealand has shock absorbers 2 Landslides and avalanches Ground on steep slopes gives way tumbles downhill 3 Sediment liquefaction Shaking of sediment containing pore water water trapped Between sediment grains l unstable quotslurryquot 0 Ex 1964 Alaska earthquake M 85 Turnagain Heights subdivision anchorage Can create sand volcanoes 4 Fires Spread from stoves lamps broken gas lines Ex 1906 San Francisco earthquake 500 blocks burned fown 20x more destructive than shaking Ex 1923 Tokyo earthquake 5 Tsunamis Japanese for quotharbor wavequot commonly called quottidal wavesquot have nothing to do with tides De nition Giant wave caused by submarine fault submarine landslide and submarine volcanic eruption and bolide impact in ocean Sudden vertical displacement of sea oor generates wave in overlying water Height of tsunami depends on earthquake magnitude and volume of sea oor displaced In deep water wave height is very small less than 12 m but is moving whole body of ocean Waves travel very fast up to 800 kmhr Tsunami carries a tremendous amount of energy As waves approach shore friction with sea oor causes wave to slow and pile up Normal tsunami reach heights up to 10m 30 ft Landslide and impactgenerated megatsumami can get 1020x bigger Asian Tsunami December 2004 Indian Ocean 0 19002000 AD 50000 people killed by tsunamis December 26 2004 250000 people killed 0 M 90 earthquake on subduction zone off coast of Sumatra o 600 miles of fault moved vertically 30 feet 0 Major issues 1 It was Christmas vacation 2 No warning 0 Indian Ocean did not have a tsunami warning network only the Paci c did 0 As ofJune 2006 Indian Ocean does as well Class 11 Friday Tsunamis 0 Were nding people weeks after the events 0 Dealing with tsunamis 1 Tsunami Prediction Seismographs record initiating earthquake that give epicenter location and earthquake magnitude 0 An oceanwide array of instruments detects passing tsunami whole oceanbody motion gives speed Tsunami warning issued 0 Problem can t predict 2 Minimizing tsunami damage 0 Identify tsunami runup areas 0 Avoid new development in high risk areas 0 ex Shoreline areas of Hilo Hawaii that were devastated in 1946 have not been rebuilt were converted to parks Class 12 Monday Class 13 Wednesday 0 Contents were all together and then cracked on the surface and magma began to rise up through the cracks as plates moved 0 2 Failed rift valleys 0 New Madrid Seismic zone 18111812 there were 5 quakes gt M8 Changed course of Mississippi river Large sand volcanoes Severe aftershocks for months 0 St Lawrence River 0 3 Extensions of midocean ridge fracture zones 0 Created as transform faults between segments of spread ddges 0 Once formed remain as structurally weak zones 0 Positives vs Negatives 0 Positive Big intraplate earthquakes are much less frequent than plate boundary ones 0 Negative when they happen their effects usually extend much farther from epicenter Earthquake prediction 0 Longer term Identify seismic zones geographic cluster or belts of historical epicenters Areas of particular risk seismic gaps section on an active fault which haven t moved for a number of years 0 Shorter term Foreshocks cluster of small earthquakes immediately preceding a large earthquake initiation of small ruptures Induced Earthquakes o Earthquakes caused by human activities 0 Most happen in areas that are already experiencing geological stress 0 Usually due to changing the stress eld of the area OR increasing pore pressure of water lubrication of locked faults o 1 Reservoirs up to M 65 Loading higher water pressure Lines of evidence Epicenters located under reservoir 0 2 Withdrawal of oil or water Changes stress eld often due to ground subsiding o 3 Deep well injection Pumping uids deep into ground why 0 Oil recovery 0 Waste disposal o 4 Rock bursts up to M 4 Caused by mining activity creates a sudden implosion of mine tunnel walls 0 5 Underground nuclear testing lnitial detonations up to M 6 Also of concern are aftershocks creation of new faults Class 14 Friday Volcanic Eruptions Volcano from Mediterranean island Vulcano off W coast of Italy 0 Ancient romans thought eruptions happened when Vulcan god of re stoked p his forges to make weapons for the gods Lava molten rock at earth s surface Magma Molten rock below the surface 0 For a volcano to form must have a magma source below the surface 0 Most volcanoes are on divergent or convergent plate boundaries 0 Divergent upwelling of mantle material 0 Convergent melting of subducting plate 0 Other source of magma for volcanoes 0 Hot sports deep mantle source of molten material not associated with plate boundaries 0 Volcanoes that form quothot spot tracksquot trace direction of plate motion relative to underlying deeper mantle Ex Hawaii latest volcano in Hawaiian Island Emperor Seamount chain 40 degree bend in this other Paci c hot spot tracks record change in Paci c plate motion 40 million years ago 0 Products of Volcanic Eruptions o 1 Lava ows viscosity resistance to ow depends on composition of lava Magma source Mantle up to oceanic up to continent Increasing Si02 is more resistance to ow 0 Increasing amount of quotvolitilesquot means more explosive behavior Hawaiian Lava ows 0 Have different Hawaiian names depending on nature of ow 0 Pahoehoe uid ropy texture warm surface when moving faster 0 Aa ruby blocky texture ow moves after surface has solidi ed l breakup into angular fragments slower o Pahoehoe and aa are both ma c in composition ow Si02 low viscosity ow readily 0 Intermediate composition ows more viscosity o Silixix high Si02 ows most viscous can plug volcano Example obsidian quotVolcanic glassquot quickly cooled cilicic lava Class 15 Monday 0 2 Pyroclastic debris quot re piecesquot 0 Fragmented material thrown from a volcano which is solid by the time it lands 0 Smallest size is volcanic ash Most 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 quot volcanic Winterquot Examples 0 1 Mount Pinatubo Philippines 1991 o ash gases ejected 30 km into atmosphere 0 lowered global temperatures for 2 years 0 2 Tambora Indonesia 1815 o 25x Mount St Helens o 1816 quotYear without a summer in a northern hemisphere o Famine in Europe and China 0 Spectacular sunsets turner paintings o Gloomy days Mary Shelley wrote Frenkenstein o 3 Eruptions 11 million years ago in Idaho 0 covered half of North America with more than 6 ft of ash o ashfall fossil beds Nebraska 0 ying through volcanic ash can seriously damage or down jets 1989 eruption of Redoubt volcano in Alaska downed a 747 o 4 Eyjafallajokull lceland 2010 o Eruption of volcano AprilMay 0 Early lavadominated eruption changed to large quantities of ash which were then carried by upper level winds toward Europe 0 Air travel across Europe was shut down largest distribution there since WWII o Pyroclastic ow Ash mixes with air forms a superheated fastmoving avalanche Aka nuee ardente French for quotglowing cloudquot Examples 0 Eruption of Mont Pelee Marinique West Indies in 1902 o Silicic spire acted as a quotchampagne corkquot 0 Fine ash fell as spire worked its way upwards o quotPoppedquot early morning and the pyroclastic ow Cloud of burning ash gas and cinders 200450 degrees C Rode cushion of air at top speeds of 300 kmhr o Slammed into capital city of St Pierre 2 minutes later 0 Only 2 out of 28 000 people survived Vesuvius Bay of Naples Italy 79 AD 0 Buried cities of Pompeii and Herculaneum in pyroclastic flows 0 Pompeii is 6 miles from Vesuvius and Naples is 9 o Lahar volcanic mud ow Ash and debris mix with water water often from snow melted by eruption Forms a slurry which is a thick watery mixture Flow down valleys or river channels at speeds up to 50 kmhr Examples Armero Columbia 1985 o Eruption of Nevado del Ruiz predicted weeks in advance Class 16 Wednesday 0 3 Volcanic Gases 0 up to 10 of magma s composition 0 Main gases H2O Water C02 carbon dioxide 0 Can kill by suffocation 0 Example Lake Nyos Cameroon 1986 0 1700 people killed all other animals 02 sulfur dioxide Converts to sulfuric acid 0 Example Souddriere Hills Montserrat 1998 o Eruption gave off 1000 tons of 02 per day H2S hydrogen Sul de rotten egg smell 0 Instantly toxic at concentrations greater than 01 shuts down respiratory amp central nervous systems Gases trapped in cooling lava create quotvesiclesquot cavities in rock 0 Pumice volcanic glass with so many vesicles that some oats 4 Jokulhlaup Icelandic o Glacial outburst ood caused by volcanic eruption underneath glacier 0 Typical sequence of events Eruption melts huge volume of water Water is initially trapped by surrounding ice and topography Water eventually nds its way out in a dramatic largescale event can be far from starting eruption 0 Places with large scale glaciers volcanoes Antarctica Iceland Yellowstone quotSupervolcanoquot 0 Current location of a continental hot spot that has been active for at least 16 million years 0 Last eruption 600000 years ago ejected 240 cubic miles ofdeb s o Collapse of giant magma chamber created a 28 x 47 mile caldera almost half of Yellowstone National Park 0 Ash deposits as far away as Missouri northern Mexico 0 Eruption Prediction 0 Shortterm weeks to months prediction of impending eruptions is often possible because many volcanoes give off warning signals 0 1 Increased heat ow Magma moving near surface can melt snowice sometimes trigger oods lahars o 2 Change in Shape Upward bulging 0 Mount St Helens bulges 15 mday in the days before erupting o 3 Earthquakes movement of magma up through country rock I earthquakes Earthquakes get stronger and closer to surface as magma rise weeks days before eruption o 4 Gas and steam emission escaping from magma or heating up groundwater Class 17 Friday Controlling volcanic hazards o 1 Risk Assessment De ne areas around volcano that lie on path of lava ows pyroclastic ows and Iahars River valleys that start on volcano slopes are particularly dangerous 0 2 Evacuation Plan 0 3 Diverting Flows Flow channels Sakurajima Japan since 1955 has erupted 100200 times per year Freezing in place Heimay Iceland 1973 0 Positive aspects of Volcanic activity 0 1 Geothermal power clean nonpollutingsource of energy that takes advantage of Earth s internal heat Is economically feasible only where the geothermal gradient increase in temperature with depth is high Near magma chambers the magma heats groundwater Can be pumped out and run through pipes to heat houses and spas 0 Example Iceland 0 As it rises hot groundwater decompresses and turns to steam 0 Used to generate electricity with turbines 0 Example Geysers geothermal eld N California supplies electricity to San Francisco 0 2 Formation of economically signi cant deposits Including precious metals and gemstones o 3 Creation of fertile soils weathering of most volcanic rocks creates very fertile soils 0 example Indonesia volcanic island chain caused by subduction FINAL EXAM MATERIAL Class Monday Landslides and other mass movements Ch 8 0 Mass Movement 0 Gravitycaused transport of material rock soil sediment snowice o Happens when slope becomes steeper than the quotangle of responsequot Angle of Repose Steepest slope Beside slop angle other factors affecting likelihood of mass movement are 0 1 Vibration earthquakes o 2 Presence of water Lubricates Increases chances and speed of movement 0 3 Vegetation can stabilize slopes decreasing movement 0 Major types of mass movement slowest to fastest 1 Creep Gradual downslope movement of sedimentsoil Moves up to a couple cm s per year 0 Due to gravity freezethaw cycles in temperate climate 2 Slump Block of material detaches along a spoon shaped sliding surface called a glide horizon and slips downslope in semicoherent fashion 3 Mud ow Debris ow 0 Follow river valleys Move up to 100 kmhr 4 Avalanche turbulent cloud of debris mixed with air he rushes down steep slopes at high velocity snow avalanches 5Landste Bedrock detaches from slope and moves quickly downhill on glide horizon that parallels slope surface 0 Can move up to 300 kmhr o Fastest when cushion of trapped air causes mass to move like a hovercraft If a large landslide hits a body of water it can generate a megatsunami tsunami many times bigger than ones generated by earthquakes Highest potential for landslidegenerated megatsunamis are volcanic islands 0 Example Hawaiian Islands 0 Example La Palma off W coast of Africa shows signs of major slope instability o Megatsunami it could generate would take about 6 hours to reach Miami Methods to Stabilize slopes Common along roads 0 1 Retaining walls Avalanche Shed Rock Bolts Terracing Relocate water ows Lower water table dries out glide horizon Ripraps absorb wave energy along coasts O oowowpIpwm
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