Midterm Study Guide
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This 18 page Study Guide was uploaded by Celeste Balboni on Tuesday February 24, 2015. The Study Guide belongs to GSC 106 at a university taught by Dr. Hood in Fall. Since its upload, it has received 67 views.
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Date Created: 02/24/15
GSC 106 Midterm Study Guide Wednesday February 25th 1 Solar System A Inner planets vs Outer planets 1 Inner planets a Mercury Venus Earth Mars b Terrestrial planets 1 Earthlike rocky surfaces 2 Outer planets a Jupiter Saturn Neptune Uranus b Gas giant planets B Astronomical Unit 1 1 AU distance from the Earth to the Sun a 93 million miles 11 Extraterrestrial Threats A Space Weather 1 Sun s corona a Outermost layer of the Sun b So hot that it shoots out continuous stream of protons called solar wind 1 Solar wind characteristics a Speeds up as it moves away from the Sun due to gravitational pull i Mach 3 at Mercury gt Mach 9 at Pluto b leaves corona at different speeds i depends on Sun s magnetic field because wind is charged particles ii Stripes of different speeds c Sun s rotation gives its magnetic field and solar wind a spiral form 2 Sends out large disturbances a Solar storms b Corona Mass Ejections CME s i Very large powerful fast ejections of material ii Move out in a given direction 1 Only some come toward us takes about 3 days 2 Earth system response to Space Weather a Earth s magnetic f1el de ects the majority of the solar wind coming toward us 1 Changes the magnetic field shape to a teardrop 2 Some charged particles get channeled toward North and South Poles a Particles follow magnetic field lines b Then react with atmospheric gases gt light emissions i Northern Lights Aurora Borealis ii Southern Lights Aurora Australis b Negative effects of CME s 1 push back protective envelope of Earth s magnetic field 2 Auroras brighter extend farther from Poles 3 Satellite failure a Fires circuits 4 Disrupts communication and navigation systems 5 Overload power grids at high latitudes 6 Radiation hazard for astronauts 7 erode ozone layer which protects us from UV radiation 8 Radiation exposure in passenger jets ying highlatitude routes a Same radiation as up to 1OO chest xrays Sunspot cycles periodicity 1 Solar activity varies in 11 year cycles 2 More solar activity gt more dark spots on the sun 3 Cycle length is predictable strength is not 4 Solar Max times of highest solar activity a Last solar Max 20122013 B Bolide Impacts 1 De nitions 3 b C d 1 Comet a small solar system body made of ice and rock and displays a long tail of gas and dust when warmed by the sun Asteroid a small solar system body less than 1000km made of rock or metal that does not orbit a planet Space dust smaller than asteroid most O5 microns really small 1 Can cause dings to space shuttles Bolide any asteroid or comet that enters Earth s atmosphere and explodes or impacts Meteor bright streak seen in sky when piece of extraterrestrial material asteroid comet space dust enters Earth s atmosphere 1 Shooting star 2 Not actual stars Meteoroid an object causing a meteor streak 1 What the shooting star actually is g Meteorite a meteoroid that makes it to Earth s surface 2 Comets 3 Composition 1 Made up of ice frozen gases and water and rocksdust b Orbit is highly eccentric offcenter 1 Spend most of their time far away from the sun 2 Orbit the sun out past pluto that s why they re made up of ice c Coma 1 What is it a A glowing cloud of dust and gas 2 How does it form a Thawing of ice in inner solar system heat from sun solar wind creates a coma 3 Solar winds blow coma away from the comet as the tail we see 01 Comet s tail 1 indicates direction of solar wind a Not the direction the comet is going 2 Comets leaving solar system often have a tail preceding them 3 Tail is brighter if it is new to the inner solar system a Still has most of its ice intact 4 Sometimes gas and dust form separate tails a Gases head off in direct direction of solar wind b Dust trail is bigger chunks falling behind in orbital path i When Earth s orbit intersects a comet s path gt meteor showers 1 Example Comet Temple Tuttle is the source of the Leonid meteoroid stream 2 Most meteoroids in meteor showers are less than 12 inch in diameter a They burn up in the atmosphere b Color seen is due to meteoroid composition e Sources of Comets l Comets fall into two different groups depending on the size of their orbit a Larger orbit gt longer orbital period time it takes to complete 1 orbit i Short period comets orbital period is less than 200 years ii Long period comets orbital period is greater than 200 years b Short Period Comets i Period less than 200 years ii Source the Kupier Belt 1 A ring of small icy bodies outside the orbit of Neptune 2 Estimated that there are at least 35000 Kuiper Belt objects with diameters greater than 100km a By 2003 several were discovered that rivaled Pluto in size iii Short period comets are created when a Kuiper Belt object has its orbit disturbed by forces throwing SP comets in toward sun 1 Collision with another Kuiper Belt object 2 Gravitational pull of outer planets especially Neptune iv Many have orbits that are strongly in uenced by Jupiter s gravitational pull 1 Jupiterfamily comets a Periods less than 20 years c Long Period Comets i Period greater than 200 years usually MUCH greater ii Source the Oort Cloud 1 Sphere of icy material that extends halfway to the nearest star beyond the orbit of Pluto 2 Barely feels sun s gravitational pull iii Long period comets are created when Oort Cloud bodies are perturbed from their orbits by forces throwing LP comets in toward sun 1 Movement by nearby stars and dust clouds 2 Shockwaves from Supemovas 3 Gravitational tides of the Milky Way Galaxy a Gravitational pull of passing stars iv Characteristics of long period comets 1 Randomly oriented a 50 retrograde going around the sun in the opposite direction from the rest of the solar system 2 Period can be thousands to millions of years a Most found are new to science b 510 big long period comets approach the sun each year 3 Asteroids a small rocky bodies orbiting the sun smaller than planets and moons 1 Remain solid even when passing the sun b Tend to have shorter more circular orbits c Asteroids come from the Asteroid Belt 1 A doughnutshaped ring of small bodies 23 AU from the Sun 2 Between Mars and Jupiter 3 Thought to be material that never formed a planet a Masses too small b Gravitational pull of Jupiter caused asteroids to collide and break so not able to form planets c 1 million objects in the Asteroid Belt only make up 1 of Earth s mass 4 100000 objects greater than 1km in diameter 5 12 objects greater than 250km in diameter 6 Largest object Ceres a 1000km size of Texas 7 Half are randomly distributed throughout the belt 8 The other half are found moving in families a Families share similar orbital elements b Thought to be remnants of larger parent bodies broken into fragments by early collisions with other asteroids d Gravitational pull of Jupiter can alter asteroids orbits 1 Doesn t for most asteroids because there is no relationship between orbital periods a random direction tugs cancel out 2 At particular distances from the Sun within the asteroid belt asteroids go around the sun exactly 2 or 3 times for every 1 time for Jupiter always get tugged in the same direction a These asteroids are in resonance with Jupiter 3 Over time Jupiter makes their orbit more eccentric a Pulls them out of the asteroid belt e Resonance gaps 1 Areas in the asteroid belt that correspond to 21 and 3 1 response with Jupiter are depleted in asteroids a Jupiter has changed asteroids orbits so that there are gaps in the Asteroid Belt b Main source of asteroids whose orbits travel through inner solar system Impact Craters a All major bodies in the solar system have been subjected to large impacts resulting in crater formation 1 Some have preserved a record of bombardment a Example Earth s moon b Earth surface processes destroy or hide most terrestrial impact craters that have occurred over time 1 Plate tectonics a Destroys crust at subduction zone 2 Erosion a Wears away craters 3 Sedimentation a Covershides craters due to new material c Still there are more than 160 known terrestrial impact craters 1 Most found since the 1950s 2 New ones found l per month d Impact craters are divided into two main groups depending on structure 1 Simple Craters a Smaller b Smooth bowl shape c Formation i Initial impact vaporizes center of impact site and most of projectile ii Large amounts of material is blasted outward 1 This is called curtain of ejecta iii Transient shortlived deep crater becomes partially refilled with rubble 1 The rubble is called impact breccia 2 Complex Craters a Larger caused by larger projectiles b Have a central peak or rings caused by rebound of central area e Impact diamonds 1 Tiny diamonds created by extreme pressure of impact 2 Microscopic 5 Chances of an Impact a b d e g h j Depends on the size of the object The larger the meteoroid l the smaller the chances of an impact a Because fewer of them out there 2 but the greater the damage Meaning of frequency numbers 1 Not periodicity predictable repeating pattern 2 Frequency is an average number per unit time when you take a long time period into account 3 ll000 means a On average 1 impact every 1000 years b Chances in any given year are about 1 in 100 01 Space dust 05 microns 1 Can ding space shuttles All meteoroids less than 03m lft in diameter burn up in the atmosphere Ones slightly larger 05m hit the Earth s surface a couple of times a year 1 Only smallscale damage within a couple meters Objects 1m in diameter impact Earth about once a year 1 Ones making it to Earth s surface create a crater 10m across 2 Many eXplode in upper atmosphere gt 1 kiloton eXplosion 3 Largest danger from this size impactor is that it might be mistaken for a nuclear strike 10m 30ft bolide 1 510 kiloton explosion 5X Hiroshima 2 Impact about once every ten years 3 If hit it hits a populated area would cause local fatalities 4 Most occur over remote areas or oceans 100m objects football field size 1 Serious regional effects Greater than 1km objects greater than 06 miles 1 Drastic global effects a Physical effects i Impact crater ii Shockwave iii Megatsunamis 1 If hits water 2 Tsunamis with initial wave heights up to l2km iv rain of aming ejecta 1 Could lead to regional or global fires b Climate effects i Short term weeks months years 1 Screening of sunlight by dust in the atmosphere gt impact winter a Darkness freezing temps ii Long term decades centuries possibly millennia 1 Dust settles out 2 Global warming due to immense heating 3 Drastic weatherclimate uctuations 2 Frequency of 1km impacts a l per every 30000 1 million years b Greater than 100 gigaton eXplosion greater than 100 million megatons 6 Human approaches to bolide threats a Rationale for identification plan 1 The most important first step is to identify and track potentially dangerous objects a Would give us the most lead time in planning what to do b Greater than 1km diameter gt global effects c Spaceguard Survey 1 Objective nd 90 of all NEA s greater than 1km by 2009 a In the process of looking for the bigger ones we are finding many smaller ones as well d AsteroidComet Hazard Mitigation 1 Changing path to one that is not Earth intersecting 2 Could be slowing it down or speeding it up 3 Possible Methods of De ection a Surface burst nuclear detonation i Could break asteroid into several pieces ii Increase threat rather than eliminating it b Standoff nuclear detonation i Set off at same distance from target ii Asteroid might soak up energy like a sponge c Asteroidbased rockets i Nonnuclear method ii shoving iii Lots of fuel required d Lasers i Groundbased or spacebased ii Force of laser will slightly move position of bolide e Change object s color i Build force gradually ii nudging iii paint it black approach iv Absorbs more heat Sun s energy l Photons emitted gradually affect orbit 139 Mass driver i Electromagnetic conveyor belt planted on asteroid that hurls dirt from surface g Solar sail i Large thin material that catches solar wind h Solar concentrator i Low energy way to collect Sun s energy ii Parabolic mirror that concentrates and causes Sun s energy on asteroid s surface 1 Plume of vaporized material e Factors affecting optimal solution 1 Size 2 Composition a Comet stony or metallic asteroid 3 Other physical properties a One solid mass or rock pile 4 Movement a Speed spin 5 Intercept distance time a More advance warning more options available i Less than 10 year warning probably nuclear b Warning time for most longperiod comets is less than 1 year i More than 10 year warning many options 1 Including ones with many visits or passings III Effects of Plate Tectonics A Earth s interior 1 2 Early segregation of earth denser material moved to center light to outside Temperature and pressure increase as you move from Earth s surface to center a Center 7 OOO F Earth made of concentric layers Internal structure a Crust 1 Solid b Mantle 1 Semiplastic c Core 1 Outer a Liquid 2 Inner a Solid Important aspects of Earth s layers a Convection in the liquid iron outer core creates Earth s magnetic field 1 Protects living things on Earth s surface from solar and cosmic radiation b Convection also occurs in the mantle due to heat input from below 1 Causes rigid layer above mantle to break into plates that move relative to each other plate tectonics a Earth s crust consists of 20 major plates plus many microplates i All moving relative to each other ii Boundaries between plates are tectonically active 1 Volcanoes earthquakes b Types of relative motion at plate boundaries i Divergent 1 Moving apart 2 Crust created a spreading ridges 3 Shown on maps by two parallel lines ii Convergent 1 Coming together a Usually one plate overrides the other b Other plate that is being forced back down into mantle is being subducted 2 Crust being destroyed 3 Shown on map by line with triangles cold front a Tips of triangles point in direction subjecting plate is plunging down iii Transform 1 Moving past each other 2 Crust neither created or destroyed 3 connect other boundary types 4 Shown on maps by a single line B Earthquakes 1 What is an earthquake a An episode of ground shaking b The motion produced when 1 Stress within Earth builds up over a period of time until it exceeded strength of rock 2 Rock fails by breaking along a fault 3 Fault a Fracture in Earth s crust on which slipsliding occurs i One side moves relative to other ii Example Transform fault San Andreas Fault b Some are vertical but most slope at an angle i Fault plane c Movement on most faults occur in discrete events i When force trying to move two sides overcomes frictional resistance 1 Stickslip behavior 2 Earthquake geography a Focus hypocenter 1 Center of energy release during an earthquake 2 Point at which initial rupture occurs b Epicenter 1 Point on surface directly above focus 2 Usually place with most ground motion and damage c Seismic waves 1 Movement of fault creates sudden pushpull felt by rock 2 Sends shock out from focus 3 Travel very quickly LOGO2000 times speed of sound 4 Three types a P waves i Primary waves ii Fastest iii Body waves move through the body of the Earth b S waves i Secondary waves ii Slower iii Body waves move through the body of the Earth c Surface waves i Only travel along ground surface ii Not through body of Earth iii Two types of surface waves 1 Rayleigh Waves up and down vertical motion like ocean waves 2 Love Waves side to side horizontal motion like a snake 3 Measuring Earthquakes a Seismograph l Instrument used to measure ground motion from earthquake a Pen moves oposite to ground motion 2 Use three a l for vertical motion b 2 for horizontal motion at right angles b Locating epicenter 1 Use arrival times of seismic waves 2 Order of waves a P wave b S wave c Surface wave 3 Time lag between the arrival of the 3 sets of waves increases the farther you are from the epicenter 4 Time delay between arrival of P and S waves can be used to calculate distance from epicenter a Using this distance at 3 different locations can triangulate to locate earthquake epicenter 4 Size of Earthquakes a Mercali Intensity Scale 1 De nes intensity of earthquake by the amount of damage it causes 2 Scale I to X11 1 to 12 in Roman numerals a II smallest felt by people b V wakes people up things fall c X many buildings destroyed 3 Useful when reconstructing historical earthquakes b Richter Magnitude Scale 1 Based on largest amount of ground motion 2 Takes into account distance from epicenter 3 Scale is a logarithm of amplitude a 10mm 101 M magnitude l b 100mm 102 M 2 c 1000mm 103 M 3 4 So M 5 is 10X stronger than M 4 a And M 5 is lOOX stronger than M 3 5 M lt 2 not felt 6 M 6 moderate damage 7 M 89 absolute damage 8 There are many more small magnitude earthquakes than large ones 5 Types of Earthquake Damage a Damage due to ground motion 1 Source of ground motion surface waves 2 Most motion caused by surface waves 3 Types depending on nature a Rayleigh Waves i Pass by like ocean waves ii Up and down motion b Love Waves i Pass by like snake ii Lateral side to side motion 4 Damage depends on a How close to epicenter b Nature of substrate underlying ground i Least damage solid bedrock ii Most damage loose sediments c Building construction i To minimize damage b Landslides and Avalanches 1 Ground on steep slopes gives way 2 Tumbles downhill 3 Example California coast c Sediment Liquefaction 1 Shaking of sediment containing pore water water trapped between sediment grains a Unstable slurry 2 Can create sand volcanoes a Sand erupts through overlying layers d Fires 1 Fires spread from stoves lamps broken gas lines e Tsunamis 1 Japanese for harbor wave 2 Commonly called tidal wave a But have nothing to do with tides 3 A giant wave caused by submarine fault landslide volcanic eruption bolide impact ocean 4 Sudden vertical displacement of sea oor generate wave in overlying water a Height of tsunami depends on i Earthquake magnitude ii Volume of sea oor displaced 5 Characteristics in deep water a Wave height is very small i Less than 12 m b But motion is moving whole body of water ocean c Waves travel very fast i Up to 800kmhr d Tsunami carries a tremendous amount of energy 6 Characteristics in shallow water a As wave approaches shore i Friction with sea oor causes front part of wave to slow down and the back piles up gt wave height increases ii Normal tsunamis reach heights up to 10m 3 0ft 7 Landslide and impact generated megatsnumai a Initial wave height can be 1020X bigger 8 Dealing with tsunamis a Tsunami prediction i Seismographs record initiating earthquake 1 Give epicenter location and magnitude ii An oceanwide array of instruments detects passing tsunami 1 Whole ocean body motion 2 Gives speed iii Tsunami waring is then issued 1 Problem a Cannot accurately predict sunup maximum vertical height onshore above sea level without knowing amount sea oor was displaced b Minimizing tsunami damage i Identifying tsunami runup areas 1 Height of water on shore ii Evacuation plan iii Avoid new development in highrisk areas iv Design new construction to minimize damage 1 Example tsunami barriers in Japan Earthquake locations a Most occur at plate boundaries 1 Divergent convergent transform a Divergent boundaries i All shallow focus less than 7 0km deep 1 Because molten mantle is rising toward surface ii Less intensedangerous of all boundaries b Transform boundaries i Plates moving past ii Shallow to deep focus up to 650km below that mantle moves in a more plastic fashion iii Minor to major earthquakes iv Motion on transform faults is often distributed in a complicated fashion along a series of faults 1 Example San Andreas fault in California v Stress of plate movement gets spread out farther where sections of main faults are locked stuck c Convergent boundaries i Most are subduction zones 1 Location where one plate plunges beneath another ii Earthquakes are shallow to deep focus less than 650km 1 Minor to major earthquakes iii Strongest most destructive earthquakes occur along upper surface of subduing plate as it s forced beneath overriding plate 1 Benioff Zone iv If subduing plate is going under at shallow angle then Benioff Zone earthquakes get spread out laterally 1 Example West Coast of South America v If subjecting plate s plunge angle is steep then you get a narrow zone of intense activity 1 Example Japan b Intraplate Earthquakes 1 Earthquakes that happen far away from boundaries 2 Sources of these earthquakes a Collision zones i Convergent boundary where two continental plates collide ii Neither one goes down 1 Too buoyant compared to mantle iii Example collision of Indian and Asian plates created the Himalayan Mountains b Ancient inactive fracture zones i Many are failed rift valleys 1 Present day location of some major rivers a Amazon River Niger River Mississippi River c Extensions of mediation ridge fracture zones i Created at transform faults between segments of spreading ridges 1 Once formed remain as structurally weak zones 3 Big intraplate earthquakes are much less frequent than plate boundary ones 4 But when they happen their effects usually extend much farther from the epicenter 7 Earthquake Prediction a Long term 1 Identify seismic zones a Geographic clusters or belts of historical epicenters 2 Areas of particular risk seismic gaps a Sections on an active fault which haven t moved for a number of years b Shorter term 1 Foreshocks a Clusters of small earthquakes immediately preceding a large earthquake b Initiation of small ruptures 8 Induced earthquakes a Earthquakes caused by human activity 1 Most happen in areas that are already experiencing geological stress b Usually due to mechanisms 1 Changing the stress field of the area 2 Increasing pore pressure of water a Lubrication of locked faults c Known causes 1 Reservoirs a Loading of water and increase in water pressure b Evidence i Can have M up to 65 ii Epicenters located under reservoirs iii Timing of earthquakes with high water levels 2 Withdrawal of oil or water a Changes stress eld i Often due to ground subsiding 3 Deep well injection a Pumping uids deep into ground b Do it to get last bits of oil out of reserves i Also do it to get rid of waste 4 Rockbursts mining a Up to M 4 b Caused by mining activity i Sudden implosion of mine tunnel walls c Responsible for 50 of mining fatalities 5 Underground nuclear testing a Initial detonations up to M 6 b Also of concern are aftershocks and creation of new faults C Volcanic Eruptions l volcano from Mediterranean island Vulcano a Off west coast of Italy b Ancient Romans though eruptions happened when Vulcan god of re stoked up his forges to make weapons for gods m molten rock at Earth s surface Magma molten rock below Earth s surface a For a volcano to form it must have magma source below the surface Most volcanoes are located on divergent or convergent plate boundaries a Divergent upwelling of mantle material b Convergent melting of subducting plate Other source of magma hot spots a Deep mantle source of molten material not associated with plate boundaries 1 Magma punches through plate moving above it b Volcanoes that form from hot spot tracks trace direction of plate motion relative to underlying deeper mantle 1 Example Hawaii a 40 bend in this and other Paci c hot spot tracks record change in paci c plate movement Products of volcanic eruptions a Lava ow 1 Viscosity resistance to ow depends on composition of lava a Low viscosity ows readily low SiOZ 2 Magma source 3 Hawaiian lava ows a Have different Hawaiian names depending on nature of low i Pahoehoe uid ropy texture warm surface when moving 1 Fastest lowest silica ii Aa rubbly blocky texture 1 Flow moves after surface has solidi ed gt breakup into angular fragments 2 Slower iii Pahoehoe and Aa are both magic in composition low SiOz 1 Low viscosity ow readily 4 Intermediate lava ows more vicious 5 Silicic high SiOz ows most vicious a Can plug volcanoes b Obsidian volcanic glass quickly cooled silica lava b Pyroclastic debris 1 fire pieces 2 Fragmented material thrown from a volcano which is solid by the time it lands a Can form cinder cones 3 Smallest size volcanic ash a Most of ash produced during volcanic eruptions ejected upwards into atmosphere i Eventually falls out b If ash makes it into upper atmosphere stratosphere it can encircle the globe i Larger eruptions put so much ash into stratosphere that they partially block sunlight 1 Lowering global temperatures 2 volcanic winter c Ash generated lighting displays i Due to friction d Sometimes ash mixes with other material and moves in a very different manner e Pyroclastic flow i Ash mixes with air forms a superheated fast moving avalanche ii Aka nuee ardente 1 French for glowing cloud c Lahar 1 Volcanic mud ow 2 Ash and debris mix with water a Often from snow melted by eruption 3 Forms a slury thick watery mixture 4 Flow down valleys or river channels at speeds up to 50 kmhr d Volcanic gases 1 Up to 10 of magma s composition 2 Main gases a H20 water vapor b C02 carbon dioxide i Can kill by suffocation c S02 sulfur dioxide i Converts to sulfuric acid d H2S hydrogen sul de i Instantly toxic at concentrations greater than 01 1 Shuts down respiratory and central nervous systems 3 Gasses trapped in cooling lava create vesicles cavities in rock a Can create pumice i Volcanic glass with so many vesicles that some oat e Jokulhlaup Icelandic 1 Glacial outburst ood 2 Caused by volcanic eruption underneath glacier 3 Typical sequence of events a Eruption melts huge volume of water b Water is initially trapped by surrounding ice and topography c Water eventually nds its way out in a dramatic large scale event i Can be far from starting eruption 4 Places with large glaciers and volcanoes a Antarctica Iceland 1 Supervolcano 1 Yellowstone 2 Current location of a continental hot spot that has been active for at least 16 million years a Last eruption 600000 years ago ejected 240 cubic miles of debris 3 Collapse of giant magma chamber create 28 X 47 mile caldera a Almost half of Yellowstone Park 4 Ash deposits as far away as Missouri Northern Mexico D Eruption prediction 1 Short term weeks to months prediction of impending eruptions is often possible because many give off warning signs a Increased heat ow 1 Magma moving near surface can melt snowice 2 Sometimes trigger oor or lahars b Change in shape 1 Upward bulging 2 Mt St Helens bulged 15mday in days before erupting c Earthquakes 1 Movement of magma up through country rock gt earthquakes 2 Earthquakes get stronger and closer to surface as magma rises a Weeks days before eruption d Gas and steam emission 1 Escaping from magma or heating up ground water 2 Controlling volcanic hazards a Risk assessment 1 De ne areas around volcano that lie on path of lava ows pyroclastic ows lahars 2 River valleys that start on volcano slopes are particularly dangerous b Evacuation plan c Diverting ows 1 Flow channels to de ect path 2 freezing in place E Positive aspects of volcano activity 1 Geothermal power a Clean nonpolluting source of energy that takes advantage of Earth s internal heat b Economically feasible only where the geothermal gradient increase in temperature with depth is high 1 Near magma chambers a Magma heats groundwater i Can be pumped out and run through pipes to heat houses spa ii As it rises hot groundwater decompresses and turns into steam 1 Used to generate electricity with turbines 2 Formation of economically significant deposits a Including precious metals and gem stones 3 Creation of fertile soil a Weathering of most volcanic rock creates very fertile soils
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