formation formation classified hamilton group member formation simply middle age unit marine rock found eastern north_america named distinctive near village new_york united_states extends basin contains largely natural gas reserves proximity high demand markets east_coast united_states makes attractive target energy development export lowest unit age hamilton group divided sub units black dominant contains lighter limestone layers sea level variation deposition million years ago black deposited relatively deep water devoid oxygen sparsely fossils contained limestone members fossil record layers provides important insights black contain iron ore early economic development region environmental hazards easily eroded presenting additional civil environmental engineering challenges geology description formation black contain limestone beds concentrations iron structure moderately developed like tends split easily plane property known lighter colored upper portion formation tend split small thin edged fragments exposure fragments exposure air tiny crystals reaction limestone particles fresh develop secondary orange pale yellow bloom associated acid rock drainage especially abundant near base upper contacts crystals occur organic rich deposits contains radioactive decay makes source rock radioactive gas measured total organic content formation ranges eastern new_york central state contain carbon support organic rich black old contain coal formed land plants petroleum geology black important source rock filled conventional petroleum formations unconventional gas reservoir seal traps underlying conventional natural gas west formation produce liquid petroleum heating deeper burial million years ago cracked oil gas extent found plateau region northern basin north_america united_states runs southern tier finger lakes regions new_york northern western pennsylvania eastern ohio western maryland west_virginia extending state line extreme western virginia bedrock eastern pennsylvania extends delaware river extreme western new_jersey exists small portion kentucky tennessee lake found crossing border canada stretches port stanley long point thomas southern ontario appears northern margin formation central new_york joint planes nearly right angles making cracks formation run perpendicular plane lies level joints form smooth nearly vertical cliffs intersecting joint planes form projecting corners rock faces exposed faces lose organic carbon turning black dark gray lighter shade gray contain small beds resemble coal new_york south pennsylvania new_jersey extensively excavated early 19th century great expense false hope finding coal perry county pennsylvania river false coal beds thick produce valuable fuel despite considerable effort expended surrounding hills marine plants probably formed false coal true coal formed terrestrial plants began appear later fossils close proximity surface bedrock south new_york makes east west band running city syracuse high risk area indoor air surface northern eastern margins formation descends depths surface southern pennsylvania structural geology beds exposed sections folded ridge valley including flanks axis broad south central pennsylvania exposed beds nearly horizontal plateau form slightly overturned beds found wind gap pennsylvania heading south dip beds vertical river nearby gap area pennsylvania extensively beds overturned reverse dip angle south fine near middle formation classified slope beds west form west facing slopes ridge west flank mountain eastern panhandle west_virginia eastern limb beds east shallower angle form steep slopes east warm springs ridge geology easily eroded found underlying low areas ridges forming linear valleys moderate relief bedrock surfaces typically covered erosion higher erosion resistant strata form surrounding higher ground soils formed hamilton deep free stones suited agriculture sampling soil formed bedrock showed dominant consisted phases appearing depths closer bedrock beds soft capture streams rivers relatively straight segments strike valleys creek creek foot long straight section lost river west_virginia port new_york ridge delaware river valley follows southwest strike eroded beds pennsylvania new_jersey state line end ridge bend delaware water gap national recreation area buried valley delaware flows bed glacial till buried eroded bedrock glacial period buried valley continues strike southwest bend pennsylvania northeast port hudson_river route delaware hudson canal deposition early mountains rising black gray hamilton group began accumulating erosion mountains deposited sediments land sea formed deposits relatively deep oxygen trough formed parallel mountain chain fragments rock carried streams ancient delta river delta probably similar present day delta africa smaller particles remained suspended longer sea flowing offshore slow persistent underwater finally came rest basin hundreds meters shore depths beneath surface alternatively basin shallow metres warm water sufficiently oxygen rich surface water mix water deposition produced black deposited deepening conditions basin floor dropped mountains rose dark formed fine mud deposited deep water buried underlying limestone beds deepening sea cut supply form limestone organic matter probably dominated settled normal decay process environment preserving organic carbon incorporated organic meaning deposited time introduced formation later organic matter trace elements including sensitive elements deposited period development land plants atmospheric oxygen increasing resulting reduction carbon dioxide atmosphere deposited named members reflect composite sequences general upward cycle continues base formation lighter limestone members attributed relatively short term basin depth later deep water sequences formed formation formation age geological occurs middle period era dating sample pennsylvania placed age million years old sample million years old relative age dating places formation subdivision stage million years ago union springs member base new_york dated end stage immediately preceded dark formation mark event late stage marine event associated extinction event pennsylvania geological survey begun henry darwin rogers classified lower black slate numbered viii new_york state geological survey begun year james hall established term report titled county professor hall argued geological names based observed characteristics vary place place need revision future favor location based nomenclature rock group receive place best developed arguments proved location based group names published based new_york adopted second pennsylvania survey widely accepted new_york survey placed hamilton group base division new_york system taxonomy obsolete current practice formation classified basal unit hamilton group lying beneath formation member group pennsylvania maryland new_york middle age divided separated formation dark thin limestone bed west_virginia separated brown occasional sandstone beds lie directly younger late formation lateral represents gap geological record period erosion non deposition eastern ohio hamilton group lies beneath member west falls formation black tongue similar characteristics underlying typically found deposited limestone formation don extends end early period contact sharp southwestern ontario canada north lake formation lateral equivalent pennsylvania forms sharp contact limestone member thin bed found base black south central pennsylvania thin green bed lies limestone eastern new_york contact present western new_york union springs member member limestone higher cherry valley limestone member rest directly absence union springs local disappearance units suggests upper contact county western new_york upper lower contact eroded away eastern west_virginia group consisting dark gray green grades westward south west hamilton group grades formation southern west_virginia virginia grades lower tennessee underlying formation south mason line difficulty limited available initial uncertainty new_york survey mapped formation unit containing middle strata named exposure west_virginia established tracing new_york pennsylvania maryland west_virginia principle scientific priority classification obsolete underlying members found grouped map unit ash beds unit thick consists relatively thin volcanic ash falls included base eastern pennsylvania described named hall years passed eventually named natural gas field county pennsylvania encountered drilling gas wells regional marker identify equivalent strata difficulty correctly identifying different ash falls period collected beds led virginia new_york widely distributed running central northern parts basin extent exceeding km2 explosive associated originating near present day central virginia released ash atmosphere dispersed michigan illinois basins southern trade winds area southern hemisphere period volcanic origin ash evidenced distinctive ash deposited directly water angular grains differ sediments rounded erosion process carries sea volcanic ash settled components producing distinctive rock appear formation gray brown black olive bed parting consisting coarse crystal sand sized ash bed zone consists ash beds labeled according order oldest youngest bed known middle coarse zone basal beds found beds limestone ash bed western new_york state ash bed marks boundary members formation central state southern basin ash beds actually indicates deposition began earlier ash beds represent single time thickness maximum thickness ranges new_jersey canada west_virginia formation thick extreme eastern pennsylvania thick west thick ohio river feet county ohio convergence east west caused decreasing grain size deposits entered basin east beds finally pinch westward deposition limited cincinnati arch formed west shore basin formation relatively thick divided members formation continues east members divided workers chose classify classify members separate formations named members local limestone member inter limestone divides eastern pennsylvania equivalent cherry valley limestone member new_york consisting skeletal intervals lower massive limestone layer thick limestone upper limestone layer named members include cardiff sandstone union springs limestone hollow limestone union springs cherry valley creek merge beneath lake bell quarry limestone ontario union springs organic rich gray black layers thin bands east member darker organic fewer limestone layers west union springs beds thin upper merging cherry valley member regional appears western new_york union springs lenses reappears northwest pennsylvania northeast ohio cherry valley western central new_york member dark grey black organic rich creek unlike region gray creek gradually west east divides cardiff member lying member central new_york organic rich black member base member lies hill bed highly limestone east cardiff divides members base dark relatively rare fossils thin zone lies grades gray sandy fine gray south central pennsylvania mapped members base member dark gray grayish black turkey ridge member olive dark gray fine medium sandstone member dark gray grayish black places near base turkey ridge commonly mapped formation included formation adjacent map sheets extreme eastern pennsylvania creek member dark gray dark gray limestone appears hollow union springs layer thick fossils relatively sparse marine fauna found fossils important example contains oldest known diverse collection thin shelled having preserved shell extinct shelled swimmer similar squid appearance fossil record life land enters fossil record trees floated sea preserved black fossils include specimens large like external plant like animals related known sea found formation partially filled found small conical commonly found member hill bed contains including coral like small incorporated turnover fauna replaced hamilton fauna member contains preserved lived benthic zone marginal marine open marine environments existed west ancient delta fossil record member shows base dominated deposit upper layers dominated filter finer sediments base member contain abundant organic matter deposit tend foul gills filter suspended sediments contained organic matter support deposit base eastern new_york coral bed found coral bed seen near new_york diverse like fauna occurs limestone cherry valley member known rich fauna originally named limestone produces remains shells larger metres contains graveyard valley eastern new_york unusual accumulation abundant straight shells types large adult cephalopods bed lacks juvenile fossils indicating behavior similar modern squid area cephalopods reproduced died interval provides excellent example sudden appearances fossil taxa relatively thin sections rock unit cherry valley taxa instead thin limestone bed contains different species cherry valley union springs contain preserved economic impact natural gas natural gas trend encompasses square miles stretches pennsylvania west_virginia southeast ohio upstate new_york largest source natural gas united_states production growing rapidly example gas natural gas trapped low requires completion method hydraulic allow gas flow bore surge drilling activity generated economic benefits environmental concerns considerable controversy iron base bed black green bed reacted form iron far ground water necessary conversion penetrate converted usable brown iron ore near bedrock surface iron ore actively mined south central pennsylvania discovery late 18th century supplanted rich ore beds iron range minnesota early 20th century ore easily located worked shallow pits shafts usable upper deposits removed shaft entered bed far surface deposits found ore converted pig iron fired stone blast constructed river region near ore deposits formations iron products area known iron produced period american revolution american_civil_war blast important economy region time cold blast stone typically employed inefficient consumed significant amounts timber nearby hardwood forests ultimately led demise typical ore imp produce pig iron produce thousand pounds day required logging acre forest daily ore varied thickness thin disappearing altogether places beds quality ore varied profitable built near iron ore mines abandoned ore timber resources fuel scarce ore found black contained relatively high proportion carbon burned produced usable red short iron red short iron undesirable properties easily tendency crack especially heated red hot state locations pennsylvania quality ore good relatively deep veins containing iron low virginia ore occasionally contained produced characteristic green flame consumed deposited hard mass known built time near removed periodically iron drainage reacted deposited form iron near 19th century iron ore deposits mineral paint pigment heated finely ground mixed oil paint exterior wood covered bridges railroad cars addition iron sloped locations eastern pennsylvania brown found lying bedrock buried beneath soil deposits excavated mineral paint time bed paint ore found directly actually underlying formation iron rich waters springs near base pennsylvania believed healing powers native americans springs hotel mineral spa built series mineral springs including iron spring springs hotel built nearby mineral springs including spring resort iron rich waters prescribed related complications mineral springs contain iron form dissolved iron gives waters slightly taste uses locally aggregate common fill suitable purpose acid rock drainage expansion 19th century roadways considered superior road metal fine fragments packed tightly drained rain dark necessary worked low grade slate eastern pennsylvania 19th century inferior formation slate south abandoned significant operation lancaster county black slate monroe county pennsylvania school students 19th century rural schools possible target carbon capture storage global warming carbon carbon dioxide greater rate carbon dioxide injected formation geological recover additional natural gas process analogous enhanced coal bed recovery practical value theoretical technique known scientists believe allow shallower depths absorption deep formations surface maintain liquid state engineering issues cut fill road construction virginia pennsylvania resulted localized acid rock drainage newly exposed cut face rapidly allowing air water rock resulting acidic surface runoff precipitation events acidic runoff aquatic ecosystems highly acidic soil contaminated runoff support vegetation lead problems soil erosion natural smaller fragments affect slope stability necessitating shallower slopes require material disturbed cut fill work acid rock drainage problem cut material fill beneath roads structures expansion problem ash beds contain clay presents landslide hazard rock damage structures constructed fill consisting caused expansion acid runoff reacting produce double volume minerals produced reactions include reactions generated pressure order kpa pounds square foot able generate times pressure foundations story building limestone acid drainage actually expansion problem promoting reactions form minerals higher volumes drilling hamilton group problematic relatively low density compatible drilling relatively fragile fracture pressure causing problem circulating drilling fluid known lost circulation formation drilling process


eruption eruption referred eruption eruption major catastrophic volcanic eruption volcanic index dense rock equivalent dated mid second millennium bce eruption largest volcanic events earth recorded history devastated island called including settlement communities agricultural areas nearby islands coast crete related earthquake clear ancient records eruption inspired certain greek myths caused turmoil egypt alluded chinese chronicle eruption background geological evidence shows volcano erupted numerous times thousand years eruption repeating process volcano violently eventually collapse roughly circular filled numerous small islands forming circle slowly building new volcano erupted collapsed ongoing process immediately prior eruption walls formed nearly continuous ring islands entrance lying tiny island eruption centered small island north existing island centre existing northern volcanic ash lava collapsed magnitude research team international scientists revealed event larger original estimate dense rock equivalent total volume material erupted volcano published estimated excess volume approximately eruption volcanic index volcano ejected times recorded eruption volcanic events subsequent probably island occurred mount volcanic eruption lake eruption mountain eruption released material atmosphere historic times sequence thick layer white soil clearly ground level prior eruption layer distinct bands indicate different phases eruption studies identified major eruption phases minor fall ash layer lack noticeable erosion layer winter rains layer deposited indicate volcano gave local population months warning human remains found site preliminary volcanic activity probably caused island population flee suggested months eruption experienced earthquakes damaged local settlements intense activity major phase eruption deposited ash minor component southeast east archaeological evidence indicated burial man structures limited damage second eruption phases involved flow lava fountain activity possible generation man structures buried completely destroyed phase characterized initiation collapse fourth major phase marked varied activity rich base surge deposits debris flows ash fall deposits phase characterized completion collapse produced process known statistical analysis indicates formed eruption area island smaller southern eastern coastlines appeared eruption landscape covered sediments places coastline vanished thick recent coastlines extended sea eruption island characterized intense phase progressively removed higher altitudes lower ones eruption resulted estimated high ash extended addition underlying volcano came contact shallow marine resulting violent steam eruption eruption generated high devastated north coast crete away affected coastal towns building walls knocked alignment island east ash layers deep found layers slopes sea level mediterranean deposits caused eruption ash layers lakes turkey heaviest east northeast ash found crete known phase eruption weeks months main phases little impact island ash deposits time claimed found delta known eruption dating eruption key marker bronze age chronology eastern mediterranean world provides fixed point entire chronology second millennium bce evidence eruption found region despite evidence exact date eruption difficult determine archaeologists traditionally placed approximately bce dates including analysis olive branch buried beneath lava flow volcano gave date bce bce confidence interval suggest eruption date century earlier suggested archaeologists dates archaeological dates substantial disagreement proponents archaeological date argued archaeological evidence consistent date early bce reducing years conversely dates argued inaccurate scientific grounds argument particular primary problem carbon sourced environment easily affected dates relative chronology archaeologists developed late bronze age eastern mediterranean cultures origin artifacts example items crete mainland greece cyprus found archaeological layer artifact origin accurately dated gives reference date layer found eruption associated given layer culture use date layer date eruption culture time destruction similar late culture crete establish chronology eruption late late cultures yielded fragments palestinian middle bronze vessels felt confident calculations rejected early dates 1970s suggested date century earlier traditional dates tell egypt found location dated bce closer traditionally accepted date eruption matches composition eruption contentious 1990s represents prominent supported date differ old chronology ice tree rings greenland ice evidence large volcanic eruption bce suggested associated volcanic ash retrieved ice core match expected late eruption mount volcano alaska believed source minute volcanic glass greenland ice core method establish date eruption tree ring dating tree ring data shown large event interfering normal tree growth north_america occurred years bce evidence climatic event bce found studies growth depression european oaks ireland sweden pine frost rings indicate date bce supporting late bce dating procedural changes ice interpreted bring data line numbers climatic effects philip asserted eruption caused significant climatic changes eastern mediterranean region sea northern hemisphere david year later time indicated date eruption evidence significant climatic event northern hemisphere like failure crops china evidence tree rings cited california oaks ireland england germany trees sweden tree rings precisely date event bce historical impact civilization eruption devastated nearby settlement layer believed eruption severely affected population crete extent impact debated early theories proposed eastern half crete plant life causing starvation local population thorough field examinations theory lost credibility determined ash fell crete theories proposed based evidence found crete indicating likely associated eruption impacted coastal areas crete devastated coastal settlements theory damage sites resulted large earthquake fires caused preceded eruption significant remains found late era ash layer level unclear effects trigger downfall civilization sites abandoned settlement systems significantly interrupted immediate aftermath eruption sea power depended ships eruption likely caused significant economic effects trigger downfall civilization intensely debated conquest occurred late period military civilization functional navy equipped army capable invasion weaponry found crete demonstrates military influence years eruption archaeologists speculate eruption caused crisis civilization making vulnerable conquest chinese records volcanic winter eruption late 17th century bce claimed researchers entries chinese records documenting collapse dynasty china according bamboo annals collapse dynasty rise dynasty approximately dated bce accompanied yellow fog dim sun frost july famine effect egyptian history apocalyptic devastated egypt described attributed short term climatic changes caused eruption difficulty interpretation conventional disputed egyptian chronology ruled whilst eruption thought occurred alternatively eruption occurred second intermediate period absence egyptian records eruption caused general disorder egypt time argued damage attributed storm caused earthquake following eruption suggested caused war storm reference merely metaphor chaos attempting impose order documents depict storms clearly literal research indicates reference overcoming powers chaos darkness greek traditions eruption volcanic fallout inspired myths picked elements western folk memory tale spread westward lines compared volcanic activity citing volcanic lightning boiling earth sea breach chamber immense flame heat evidence explosions descriptions atlantis archaeological evidence myth atlantis described based eruption book exodus barbara seeks establish link eruption bce exodus egypt bible


known canada episode mountain building late involved repeated episodes continental collisions superior province minnesota river valley collided million years ago collision folded earth crust produced heat pressure rock blocks added superior province boundary stretches present day eastern south lake area brought close million years ago lasted million years marks major change development earth crust canadian shield contains belts rocks formed action volcanic rock areas individual belts consist form fault zones types belts seen volcanic origin origin lie northeastern oriented belts wide southern portion superior province slave province portions province affected million years ago combined wyoming form overview earth heat production twice present caused processes active result plates continents smaller broad blocks old found shields end blocks came form larger blocks belts form canadian shield collided million years ago superior province large minnesota river valley composed mainly granite led mountain building episode known named county wisconsin canada duration estimated million years current boundary known great lakes zone zone wide extends line roughly kilometers long middle south east middle upper peninsula michigan ontario region region remains slightly active today began million years ago end affected adjacent regions northern minnesota ontario superior province slave eastern province far wider region influence subsequent earliest north_america brought close end marks major change development earth crust crust essentially formed achieved continents collision folded earth crust produced heat pressure existing rock repeated continental collisions compression north south axis resulted uprising mountains followed granite million years ago examples sacred heart granite southwestern minnesota border wisconsin michigan upper peninsula solidified new stresses belt caused movement horizontally faults moved huge blocks crust vertically relative adjacent blocks combination folding intrusion built mountain ranges northern minnesota northern wisconsin michigan upper peninsula southernmost ontario high grade rocks associated eroded beds upward determined mountains kilometers high similar projections beds downward coupled measurements belts canada suggest rocks belts project downward kilometers action border granite bodies produces succession volcanic rocks called belts volcanic rocks concentrated belts green color comes minerals formed occurred rocks folded system mountains volcanic beds thick million years ago belt subjected new stresses caused movement faults small large scales typical belt faults vertical horizontal movement relative adjacent blocks large scale faults typically occur margins belts contact enclosed rocks vertical movement thousands meters horizontal movements kilometers occur fault zones time million years ago masses rocks heating pressing rocks hard greenish began continued intermediate rocks erupted volcanic centers ended deposition sediments erosion volcanic pile rising shallow ancient sea cooled form minnesota probably cooled depths great contain gas belts components folded original rock occurs outer margins trough younger rock units occur closer center rocks intensely folded nearly tops layers belt facing rock sequences effect lying sides folding complex single layer exposed surface times subsequent erosion volcanic activity belts forming ejected air settled sediments knife lake lake formations poorly clay derived debris presence debris suggests explosive volcanic activity occurred area earlier took place surface took place depths numerous earthquakes accompanied superior province superior province forms core north american continent canadian shield thickness date million years ago formed small ages decrease away nucleus progression illustrated age discussed individual sections later docked periphery continental masses developing fused oceanic crust general superior province consists east west belts volcanic rocks alternating belts rocks zones belt essentially large block areas individual belts fault zones consisting granite western contains regional pattern east west wide belts western superior province mantle remained intact million year ago folding seen lie northeastern oriented belts wide figure right northernmost widest province begins north central minnesota continues northeasterly central ontario partially interrupted southern province immediately south extends far west north central minnesota extends northeast completely interrupted narrow band million year old southern province northeast thunder bay southerly begins central minnesota continues northeast thunder bay ontario canada southern border north thunder bay extends east lake superior northern boundary continues roughly northeasterly heading southern border south follow northeast shore lake superior fault zones separated shear zones caused continued compression occurred boundaries major fault zones boundary controlled plates subsequent rainy lake river fault zone major northeast southwest strike slip fault zone trends cut northwest national park minnesota extends westward near international falls minnesota fort ontario fault transported rocks belt considerable distance origin belt wide seven sisters islands west pods dating rainy lake area ontario age million years old favors moving plate model formation boundary largest fault fault separating trend caused introduction masses fault traced westward north horizontal movement northern block moving eastward upward relative southern block junction zone rich rock characteristics processes indicates zone partial melting possible high temperature pressure conditions visible wide belt flattened large crystals fault indicate simple compression event docked provides evidence joined collision continental plates million years ago structures include cut limbs earlier phase cross cutting indicate undergone periods active volcanic island chain rocks derived belts surrounded cut belts consist aged million years old belt extends ontario parts minnesota dominant rocks belt produced intense minor amounts rocks sediments aged million years relatively low grade margins high grade center low grade components derived primarily volcanic rocks high grade rocks contain minerals reflect higher temperatures high grade produced ocean crust partial melting rocks immediately south national park extending fault broad transition zone contains belt represents wedge formed trench collision island arcs belts boundaries belt flanking belts north south major fault zones rainy lake river fault zones active volcanic island chain consisting belts surrounded cut belts consist sediments aged million years old rock type white coarse minerals slave province extensive regions slave province northern canada later heated surrounding rock create regions called million years ago regions typically wide creation continuous process recognizable phases established phases cycle began phase evolved second phase accompanied broad regional thermal began continued phase produced minor folding caused major resulting granite core thermal dome phase occurred lower pressure unloading temperatures extreme ranging complete thermal dome decayed minor changes occurred decay phase region effectively stable rock units establishes sequence events approximately million years duration leading formation new segment oldest rocks million years old basic largely characteristics dating indicates ages million years recorded million years major late bodies million years youngest units areas traversing near studied slave province rocks volcanic rocks ages rocks million years ago time rocks comprising slave province represent high grade intrusion basement typical rocks banding rocks uniformly hard thoroughly deformed little exists tightly folded occur province rocks forming province northeastern canada greenland separated superior narrow band rocks greenland separated north_america million years ago align canada opposite bay southern tip greenland province means connected north_america end


volcanic ash volcanic ash consists fragments rock minerals volcanic glass created volcanic measuring inches diameter term volcanic ash loosely refer explosive eruption products correctly referred including particles larger volcanic ash formed explosive volcanic dissolved gases expand escape violently atmosphere force escaping gas atmosphere fragments volcanic rock glass ash produced comes contact water causing water flash steam leading shattering air ash transported wind thousands kilometers away wide dispersal ash number impacts society including human animal health disruption aviation disruption critical infrastructure electric power supply systems telecommunications water waste water networks transportation primary industries agriculture buildings structures formation volcanic ash formed explosive volcanic transport density currents explosive occur rises allowing dissolved water carbon dioxide gas bubbles bubbles foam produced decreases density accelerating occurs bubbles occupy vol mixture occurs violently expanding bubbles tear apart fragments ejected atmosphere ash particles efficient process ash formation capable generating fine ash addition water volcanic ash produced occurs comes contact bodies water sea lakes marshes snow ice significantly boiling point water comes contact water film forms effect eventually film collapse leading direct cold water hot increases heat transfer leads rapid expansion water small particles subsequently ejected volcanic vent causes increase contact area water creating feedback mechanism leading production fine ash particles density currents produce ash particles typically produced lava dome collapse collapse eruption column density currents particle occurs particles interact resulting reduction grain size production fine ash particles addition ash produced secondary fragments conservation heat flow processes produce large quantities fine ash removed density currents ash physical chemical characteristics volcanic ash primarily controlled style volcanic eruption display range eruption styles controlled chemistry crystal content temperature dissolved gases classified volcanic index composition produce extremely explosive composition large quantities atmosphere controlling ash produced duration eruption longer eruption sustained ash produced example second phase classified despite modest high eruption column eruption continued month allowed large volume ash ejected atmosphere properties chemical types minerals present volcanic ash dependent chemistry erupted considering abundant elements found oxygen types ash produced volcanic commonly explained terms content low energy produce dark coloured ash containing generally rich iron explosive produce ash high types ash intermediate composition content principal gases released volcanic activity water carbon dioxide dioxide hydrogen hydrogen carbon hydrogen gases metals removed atmosphere processes chemical reaction dry wet deposition surface volcanic ash long recognised range primarily compounds readily fresh volcanic ash considered likely formed consequence rapid acid dissolution ash particles eruption thought supply involved deposition species reported fresh ash abundant species usually found present suggest cases elements present simple experiment ash eruption mount found readily followed compounds general exception metals compounds calcium fresh ash highly variable depending presence acidic gas primarily consequence gases eruption ash surface solid structure act conductor dissolved solution source moisture fog mist light rain etc ash electrically recent study shown electrical volcanic ash increases increasing moisture content increasing salt content increasing bulk density ability volcanic ash conduct electric current significant implications electric power supply systems physical components volcanic ash particles erupted non non particles ash produced low hawaiian produce range different dependent process example ash collected hawaiian lava consists light brown glass contain rare small crystals slightly form variety irregular black dark brown contrast high ash consists products individual crystal fraction fragments ash generated primarily consists altered mineral fragments commonly clay matrix particle surfaces coated crystals clay textures remain identify types morphology morphology shape volcanic ash controlled different eruption processes low typically form shaped particles shape controlled surface tension acceleration leave vent air friction shapes range perfect spheres variety twisted smooth surfaces morphology ash high dependent shape rising formed expansion gas solidified ash particles varying degrees particles extremely high surface area volume tubes observed grain surfaces result broken walls ash particles high typically angular fragments thin wall fragments fragments volcanic ash typically angular morphology ash generally controlled mechanical properties wall rock broken explosive expansion gases reaches surface morphology ash particles controlled stresses result glass form small glass ash particles shape density play minor role determination grain shape sort eruption rising quickly cooled contact ground surface water stresses cause dominant shape types irregular smooth surfaces moss like convoluted spherical drop like plate like density density individual particles varies different density volcanic ash varies glass crystals particles particles deposited close source fine glass relatively enriched ash fall deposits locations high density scale high degree types volcanic ash particularly high content grain size volcanic ash consists particles particles classified fine overall grain size distribution ash vary greatly different compositions attempts grain size characteristics deposit event produced predictions generally produce finer material compared higher proportions fine ash higher explosive probably size pre smaller good evidence flows produce high proportions fine ash likely process occurs inside volcanic efficient surface summit crater dispersal ash particles incorporated eruption columns ejected vent high velocity initial momentum eruption column upwards air drawn column bulk density decreases starts rise atmosphere point bulk density column surrounding atmosphere column cease rising start moving lateral controlled prevailing winds ash deposited hundreds thousands kilometres volcano depending eruption column height particle size ash climatic conditions especially wind direction strength humidity ash fallout occurs immediately eruption controlled particle density initially coarse particles fall close source followed fallout result particle column ash fallout concentrated final stages column moves results ash fall deposit generally decreases thickness grain size increasing distance volcano fine ash particles remain atmosphere days weeks dispersed high altitude winds particles impact aviation industry refer impacts section combined gas particles affect global climate volcanic ash form density currents called density currents travel away volcano smaller particles removed flow form dense zone main flow zone surrounding air formed tend higher concentrations fine ash particles compared eruption density current impacts introduction population growth caused progressive urban development higher risk areas closer volcanic centres increasing human exposure volcanic ash fall events infrastructure critical supporting modern societies particularly urban areas high population create high demand services infrastructure networks systems support urban living provide services depend health education transport social networking infrastructure networks services support variety facilities broad range sectors volcanic ash fall events disrupt damage infrastructure society depends recent illustrated vulnerability urban areas received millimetres centimetres volcanic ash sufficient cause disruption transportation electricity water sewage storm water systems costs incurred business disruption replacement damaged parts losses ash fall impacts critical infrastructure cause multiple knock effects disrupt different sectors services volcanic ash fall physically socially economically volcanic ash affect areas areas hundreds kilometres source causes losses wide variety different infrastructure sectors impacts dependent ash fall thickness duration ash fall grain size chemistry ash ash wet dry management prevention measures employed reduce effects ash fall different sectors infrastructure society affected different ways vulnerable range impacts consequences discussed following sections infrastructure sectors electricity volcanic ash cause disruption electric power supply systems levels power generation transformation transmission distribution main impacts arising ash contamination apparatus power delivery process wet deposits ash high voltage initiate current small current flow surface sufficient current achieved cause electrical discharge surface material resulting short circuit current high trip circuit breaker disruption service occur ash induced burn crack likely result disruption power supply volcanic ash pit metallic apparatus particularly moving parts water wind turbines cooling fans thermal power plants high bulk density ash deposits cause line damage steel towers wooden poles ash loading hazardous ash lines structures wet rainfall ash fall fine ash diameter lines structures readily volcanic ash load vegetation causing fall lines snow ice accumulation lines vegetation increases risk collapse lines hardware controlled outages vulnerable connection points circuits ash fall subsided cleaning equipment drinking water supplies following eruption common public hold fears chemical contamination water supplies general physical impacts tend problems caused release chemical fresh volcanic ash impacts vary according type treatment system large water treatment plants fed systems impacts airborne ash interfere operation head pumps electricity outages caused disrupt electrically powered pumps backup generation surface water sources lakes volume available species ash generally large abundant components ash occur naturally significant concentrations surface waters affected greatly volcanic low concern drinking water possible exception elements iron aluminium commonly enriched background levels volcanic elements metallic taste water produce red brown black considered health risk volcanic known caused problems water supplies toxic trace elements mercury lead occur low levels ash point note drinking water treatment commonly involves addition treatment chemicals aluminium lime adjustment compounds dental health physical impacts affect operation water treatment plants ash block intake structures cause severe damage pump pump motors water treatment plants initial step automatically adjusted level suspended measured units incoming water cases changes caused suspended ash particles normal operating range plant managed adjusting addition likely cause problems plants designed high levels treatment ash enter systems open sand filters direct fallout intake waters cases increased maintenance required manage effects service final step drinking water treatment ensure final drinking water free infectious suspended particles provide growth substrate protect treatment extremely important water treatment process good level removal suspended particles small treatment systems small communities obtain drinking water diverse sources lakes streams springs wells levels treatment vary widely rudimentary systems coarse screening settling followed usually sophisticated systems step noted high quality source secure unlikely guarantee drinking water safe relatively resistant standard require additional removal steps volcanic likely major effects systems ash intake structures cause damage pumps block pipes settling ponds open filters high levels likely interfere treatment adjusted compensate essential monitor distribution system fed supplies households small communities rely drinking water supplies roof fed systems highly vulnerable contamination large surface area relative storage tank volume cases chemical health risk drinking water recommended prior disconnected water tank protected problem surface coating fresh volcanic ash acidic unlike surface waters generally low acid capacity tank waters lead problems water aggressive materials comes contact particular problem lead head nails lead flashing roof copper pipes metallic fittings water demand events large demands commonly placed water resources cleanup shortages result shortages compromise key services lead lack water drinking municipal authorities need monitor manage water demand carefully need advise public cleanup methods use water cleaning treatment networks sustain damage similar water supply networks difficult exclude ash system systems combined storm water sewer lines risk ash enter sewer lines illegal connections roof cross connections covers holes cracks sewer pipes ash laden sewage entering treatment plant likely cause failure mechanical equipment step screens rotating screens ash system settle reduce capacity biological increasing volume changing composition aircraft principal damage sustained aircraft flying volcanic ash cloud forward facing surfaces leading edges wings accumulation ash surface openings including engines landing lights reduce visibility forcing pilots rely instruments instruments provide incorrect readings sensors tubes blocked ash ash engines causes damage fan blades ash sharp blades reducing efficiency ash chamber form glass ash turbine blades blocking air flow causing engine stall composition ash melting temperature operating temperature modern large jet engines degree impact depends concentration ash length time aircraft spends actions taken pilots critically melting ash particularly volcanic glass result accumulation ash turbine guide resulting stall complete loss engine thrust standard procedure engine control system possible stall increase power problem recommended pilots reduce engine power quickly exit cloud performing descending turn volcanic gases present ash clouds cause damage engines damage surface years occurrence instances damage jet aircraft result ash encounter june british boeing flight flew ash cloud eruption mount indonesia resulting failure engines plane descended feet minutes engines restarted allowing aircraft emergency landing december boeing flight lost power engines flying ash cloud mount alaska dropping feet minutes engines started minutes impact total damage million took months work repair plane 1990s million damage sustained commercial aircraft air ground consequence eruption mount philippines april europe affected flights cancelled unprecedented presence volcanic ash upper atmosphere eruption volcano april finnish air_force halted training flights damage found volcanic dust engines boeing fighters april raf typhoon training flights temporarily suspended deposits volcanic ash found jet engines june similar chile argentina brazil australia new_zealand following eruption chile detection volcanic ash clouds difficult detect aircraft onboard cockpit instruments exist detect new system called airborne volcanic object infrared avoid recently developed aviation daughter company norwegian institute air research allow pilots detect ash ahead fly safely system uses fast sampling infrared cameras mounted forward facing surface tuned detect volcanic ash system detect ash concentrations giving pilots approximately minutes warning camera currently tested airline company addition ground satellite based imagery radar detect ash clouds information passed meteorological agencies volcanic airline companies volcanic ash advisory centers regions world issue advisories describing current future extent ash cloud airport systems volcanic ash affects flight operations affect ground based airport operations small ash reduce visibility create slippery infiltrate communication electrical systems ground services damage buildings parked aircraft ash accumulation millimeters requires removal airports resume operations ash disappear unlike disposed manner prevents wind aircraft land transport ash disrupt transportation systems large areas hours days including roads vehicles railways ports shipping falling ash reduce visibility driving difficult dangerous addition fast travelling cars stir ash creating clouds ongoing visibility hazards ash decrease traction especially wet cover road markings fine ash infiltrate openings cars surfaces especially moving parts air oil filters blocked requiring frequent replacement rail transport vulnerable mainly caused reduction visibility marine transport impacted volcanic ash ash fall block air oil filters moving parts engines navigation impacted reduction visibility ash fall ash float water surface water quickly leading heating machinery communications broadcast networks affected volcanic ash following ways reduction signal strength damage equipment network user demand signal volcanic ash documented reports disrupted communications following eruption mount eruption research new_zealand based engineering group determined theoretically impacts telecommunications signals ash limited low frequency services satellite communication signal interference caused lightning frequently generated volcanic eruption equipment damaged direct ash fall modern equipment requires constant cooling air conditioning units susceptible ash reduces cooling efficiency heavy ash falls cause lines masts cables antennae dishes towers collapse ash loading moist ash cause accelerated metal components reports recent suggest largest disruption communication networks high user demand common natural disasters computers computers impacted volcanic ash functionality decreasing unlikely completely fail vulnerable components mechanical components cooling fans drives keyboard mice touch pads components jammed fine ash causing cease working restored working order cleaning compressed air moist ash cause electrical short circuits computers affect computers buildings structures damage buildings structures range complete partial roof collapse catastrophic damage exterior internal materials impacts depend thickness ash wet dry roof building design ash gets inside building specific weight ash vary significantly rain increase problems associated ash loading similar snow ash severe load ash generally greater ash melt ash damage especially rain fall impacts ash loading depend building design construction including roof slope construction materials roof span support system age maintenance building generally flat roofs susceptible damage collapse pitched roofs roofs smooth materials sheet metal glass likely shed ash roofs rough materials asphalt wood roof collapse lead widespread injuries deaths property damage example collapse roofs ash june mount eruption killed people human animal health ash particles diameter suspended air known people exposed ash falls experienced respiratory discomfort breathing difficulty eye skin nose throat symptoms effects short term considered pose significant health risk pre existing respiratory conditions health effects volcanic ash depend grain size composition chemical surface ash particles additional factors related potential respiratory symptoms frequency duration exposure concentration ash air ash fraction proportion ash diameter known social context important chronic health effects volcanic ash fall possible exposure free known cause minerals associated include present volcanic ash minerals described free attached element create new mineral containing thought unlikely contain exposure levels free ash commonly risk studies people work mining construction industries classified human international agency research cancer values created exposure unclear rationale guidelines air usa guidelines exposure thought guidelines exposure levels exceeded short periods time significant health effects general population documented cases developed exposure volcanic ash long term studies necessary evaluate effects lacking ash harmful livestock causing teeth cases high content poisoning toxic levels grazing animals known eruption iceland poisoning occurred humans livestock result chemistry ash gas contained high levels hydrogen following mount new_zealand thousand died affected grazing land ash fall ash cause sheep ash mount hudson volcanic eruption chile suffered weakness added weight ash wool led fatigue sheep stand environment agriculture volcanic ash detrimental impact environment difficult predict large variety environmental conditions exist ash fall zone natural waterways impacted way urban water supply networks ash increase water reduce light reaching lower depths growth submerged aquatic plants consequently affect species dependent fish high affect ability fish gills absorb dissolved oxygen occur reduce water impact fauna flora living environment contamination occur ash contains high concentrations ash accumulation affect pasture plants trees agriculture industries thin ash falls livestock eating alter growth increase pasture production effect slight effect occurred following mount heavier falls completely bury soil leading death pasture soil oxygen plant survival dependent ash thickness ash chemistry ash rainfall duration burial length plant time ash fall acidic nature ash lead elevated soil levels lowered soil reduce availability essential minerals alter soil characteristics crops plants survive ash impact crops fruit vegetables grain ash burn plant crop tissue reducing quality crops harvest damage plants ash loading young forests trees years old risk ash falls likely destroyed ash deposits ash fall unlikely kill mature trees ash loading break large branches heavy ash falls trees occur especially coarse ash component ash fall land rehabilitation ash fall possible depending ash deposit thickness rehabilitation treatment include direct deposit mixing deposit buried soil ash deposit land surface application new ash deposit critical infrastructure infrastructure services vital functionality modern society provide medical care emergency services water power transportation links critical facilities dependent makes vulnerable direct impacts hazard event indirect effects disruption impacts inter dependent vulnerability depend type hazard spatial density critical critical damage speed service restoration state repair age institutional characteristics ownership eruption iceland highlighted impacts volcanic ash fall modern society dependence functionality infrastructure services event airline industry suffered business losses billion closure european days april subsequent ash fall event known caused local crop losses agricultural industries losses tourism industry destruction roads bridges iceland combination glacial melt water costs associated emergency response clean europe losses associated travel disruption insurance industry postal service imports exports europe worldwide consequences demonstrate diversity impacts single event management involve sealing buildings protecting infrastructure homes storing sufficient supplies food water ash fall clean begin dust masks worn reduce ash respiratory health affects worn protect eye international volcanic impacts working group maintains regularly updated database impacts strategies ash home staying informed volcanic activity having plans place alternative shelter locations constitutes good ash fall event prevent impacts associated ash fall reduce effects increase human capacity cope events items plastic protect electronic equipment ash battery operated radios extremely useful ash fall events protection infrastructure considered emergency critical facilities need remain identified shut reduce damage important ash buildings machinery networks particular water systems prevent damage caused ash particles windows doors closed possible prevent ash buildings communication plans inform actions undertaken spare parts systems place prior ash fall events reduce service disruption return functionality quickly possible good includes identification ash disposal sites ash fall occurs avoid movement ash aid clean protective equipment eye protection dust masks deployed clean teams advance ash fall events effective techniques management ash developed including cleaning methods cleaning apparatus actions limit damage include covering openings air water aircraft engines windows ash fall events roads closed allow clean ash falls speed restrictions place order prevent motorists developing motor problems stranded following ash fall prevent effects underground water systems waste water networks drains ash prevented entering system ash saturated water prevent ash aid clean clean operations critical facilities coordination clean efforts constitute good management practice volcanic ash soils volcanic ash primary use soil minerals ash washed soil rain natural processes mixes soil create layer layer highly rich nutrients good agricultural use presence lush forests volcanic islands result trees growing nitrogen rich


formation formation beds consist large quantities gravel fine sediment thousand meters thousand feet volcanic columbia river group south central washington north central oregon beds consist distinct horizontal layers sediment clearly layer beds covered soils deposited later number layers varies location beds vary depth lower elevations number layers found extremely thin layers maximum elevation observed beds element chain evidence helped identify define progression floods occurred years bce floods flow gap slow water temporary lake lake lewis lake lewis flooded river valleys relatively calm arms lake waters deposited suspended materials eroded regions north lake lewis pronounced layers discovery interpretation visible rivers beds subjected study early 20th century remain center scientific analyses characterize floods type locality type locality formation confluence river river originally noted richard foster flint numerous subsequently identified basins lake lewis lake equivalent deposits present valley near portland lake early interpretation published paper arguing eastern washington caused massive flooding distant past view seen arguing catastrophic explanation development ran counter prevailing view views initially defended theories setting year debate floods view catastrophic flood finally prevailed extended argument arguing sequence multiple floods proposal based mainly analysis glacial lake deposits creek formation deposits canyon represented away single catastrophic flood series catastrophic floods flood source ascribed glacial lake controversy formed mainly multiple periodic large floods single grand scale flood late pleistocene glacial lake unidentified canadian source reappeared team reviewed sequences beds concluded sequences automatically imply multiple floods separated decades centuries proposed glacial lake basin result draining lake british_columbia north team proposed rhythmic beds result multiple single larger flood response team observed substantial evidence multiple large floods including evidence mud cracks animal lower layers beds filled sediment later floods causes recent scientific investigations support proposed separation layers records flood events sources support temporal separation floods definitively identify source water floods agree lake source formation beds formed sediment deposited floods bce flood occurred approximately bce potential source periodic flooding somewhat controversial flood release lakes british_columbia specific source identified floods flow narrow gap restricted water temporary lake lake lewis formed columbia plateau lake lewis river valleys flooding lasted period days relatively calm arms lake waters thick suspended materials eroded suspended materials settled creating thick formation layers found valleys larger settled followed finer ones resulted layers graded larger particles smaller ones studied formation wall canyon west washington counted distinct flood deposit layers floods occur glacial lake existed estimates place bce recent studies dating establish approximate ages deposition layers valleys protected violent currents main channel result flood strata laid earlier floods eroded away subsequent floods buried preserved average period flood episodes estimated years estimates based number constraints time lake depends level dam breached releasing flood adjusted precipitation rate flowing lake volumes correspond calculated maximum flow rates estimated years beds volcanic ash lie layers formation secular variation indicates beds formed floods purity suggests deposition mixed surrounding sediment deposited moving water indicates dry period ash falls hiatus floods offshore deposits bed pacific mouth columbia river include material deposited thousand year period corresponds period multiple floods seen beds floods average separation floods years number layers deposited varies location lake lewis basin best understood result multiple floods variable levels correspond lake ice dam varying lake levels releasing different volumes flood waters suggest time floods variable flood beds locations upstream lake lewis creek montana arm glacial lake columbia corresponding flood deposits deposit grading repetition lake lewis glacial lake columbia remained filled annual deposits observed flood deposits flood deposits distinguished annually deposited thickness presence materials foreign immediate drainage reports annual flood deposits lake columbia supporting period years ice dam failures additional counts lake basin river creek suggest time floods years average locations river valley formation originally identified confluence river river found distance river valley number layers observed decreases progresses valley indicating lakes varied depth distance upstream flood dams observed locations penetrating layers vertically uniform size fine materials indications period floods long deposits dried forming vertical cracks allowing wind blown eroded materials cracks river valley river valley closed basin river passes narrow gap near confluence columbia river widens broad open valley floor confluence columbia area filled varying depths successive floods sediments settled form beds basin creating today fertile farmland region lowest broader valley east columbia river west city washington soils commonly form beds locations erosion exposed beds terrace segment seen highway west formation extensively exposed canyon southwest town near confluence rivers deposits found tributaries extending distance south oregon river valley lake lewis extended valley flooding area km2 valley covering area occupied city valley extends widening westwards narrows union gap basin basin lower river contain large amounts formation deposits extensively exposed north ice commonly found beds river valley river tributary creek valleys partially filled deposits floods lie distance snake river drainage flood waters lake lewis backed drainage far deposit sediments deposits consist distinct beds fine sand deposits narrow approach valley walls central valley maximum sediment thickness elevation valley flooding events caused water valley sufficient volume deposit distinct layers columbia river basin floods observed columbia river valley notable location white deposits formed saddle mountains location trinidad located approximately miles west crescent bar road willow creek valley formation found oregon areas flooded lake lake flooded john day river valleys tributaries example sand associated floods present willow creek valley tributary columbia river willow creek columbia miles west oregon excellent unit contains abundant found highway near community cecil oregon deposits associated lake


arabic system separate limestone caves spanning overall length nearly kilometres caves situated valley locality kilometres north capital inhabited prehistoric times lower cave rediscovered reverend william visited boat channels underground river provides fresh drinking water million discovered upper galleries metres lower cave accommodated access tunnel series enable tourists safe access disturbing natural landscape upper galleries house world largest known galleries composed series chambers largest peaks height metres aside national symbol tourist destination plays important social economic cultural role country finalists new wonders nature competition location cave situated center western flanks lebanon mountains specifically valley natural entrance metres sea level located kilometres east mediterranean coastline kilometres north confines municipality history ancient found smaller cave near river suggesting cave antiquity produce swords modern discovery underground river credited reverend william american missionary ventured metres cave reaching underground river fired shot gun resulting echoes convinced found major importance engineers water company friend reverend daniel bliss president syrian protestant college later american university explored expeditions carried penetrated metres principal source supplies water hell break razor sharp rocks bliss engineers recorded names year column great limestone pillar metres entrance metres called wrote names details expedition paper sealed bottle placed lime water covered bottle thin white film permanently fixing stone expeditions carried english american french explorers expeditions brought depth metres 1940s explorers notably members club club founded pushed deeper expeditions revealed great underground system known overall length nearly kilometres lower opened public exploration underway mainly club exploration led discovery elevated dry branch later referred upper galleries club contributed study upper galleries aiming provide access tunnel dug development purposes work access tunnel begun opening followed installation series permitted tourists safe access upper galleries disturbing natural landscape concert electronic music french composer held cave celebrate inauguration upper galleries event organized artist sculptor cultural events taken place unusual surrounding including concert world acknowledged german composer november recently classical music concert armenian composer pianist guy closed public civil war tunnels leading lower upper galleries store munitions outside buildings military purposes caves reopened remain country key natural attractions referred dry cave metres deep east source cave river flows connected narrow channels noted excavated positions later excavated materials excavations museum archaeological museum american university private collection noticed upper level finds including polished pieces primitive burned bones end noted similarities finds period evidence later occupation included pot found father suggested date early bronze age levels rock shelter situated platform dry cave entrance iii excavations large number flint tools bones found excavations francis hours revealed extensive deeper richer deposits previously suspected father hours permitted disclose upper material appeared display late upper early characteristics probably including excavation continued area owned government iii deposit brown soil fell location suggested east end inside entrance tourists conducted boat found club excavated father hours flint tools found deposit geometric design suggested form later discovered displaced forms included straight oblique type micro end transverse short backs resembled found material stored museum rock shelter cliff upstream contained large quantity material looted deemed unfit excavation director study remains shelter hoped shed light communities inhabited different sites different times geology located lower middle strata thickness metres consists limestone formation exposed air local late early cretaceous strata aerial exposure buried cretaceous final mount lebanon early phase reactivated valley upper volcanic rocks lower cretaceous sand slant vertically forming barrier forcing outlet underground river surface barrier reason westernmost large cave chambers heights exceeding metres limestone intensified steep topography area volume precipitation lebanon ratio total slope gradient calculated entrance cave inland shows smooth flat course interrupted small west cave starts large halls dimension narrower going forth thompson metres long metres wide grand chaos metres long hall metres long metres wide collapsed blocks cave ends shaped pattern branch ends description caves caves formed millions years dissolution limestone limestone dissolved acid charged rain water limestone originally contains cracks produced forces water rock starts widen cracks caves inside layers longest cave complex middle_east sits metres sea level height difference metres caves provide tunnel escape route underground river principal source longest explored cave lebanon years exploration penetrated metres entry point lower far end underground river metres upper galleries upper cave upper cave overall length metres metres accessible visitors specially conceived walkway access remainder cave restricted prevent ecological damage occur tourists upper cave contains great concentration variety formations columns mushrooms ponds upper gallery famous formations lit effective lighting system entered metres long concrete tunnel accessible visitors huge chambers called white chamber second red chamber color formations white pure red color given iron small amounts lebanon iron red color instead brown color common northern countries reason different chemical reaction caused high temperature produces different kind iron white chamber medium sized impressive formations cave red chamber metres high metres metres wide chamber biggest chambers height metres longest world located white chamber measures metres long lower cave lower gallery overall length metres located metres upper gallery traversed smooth underwater river lake dark lake river broken small lower cave thompson massive hall impressive eagle halls lower gallery include grand chaos visitors transported lower gallery electric boats distance metres winter lower level closed water level high economic social importance today popular recreational cave major tourist attraction hosts approximately visitors year contributes heavily public life region firm runs important employer provides time jobs local residents female addition employment caves contribute ticket fees local municipality general revenue ministry tourism additional ticket fees ministry finance cave spring flow ranging providing fresh drinking water half million inhabitants capital water pollution domestic agricultural runoff remains concern recent analysis detected increasing presence bacteria awards french president united_nations world tourism organization world bank accorded sustainable development tourism prize company manages site summit dubbed new ties tourism culture geneva december behalf based private company received prestigious award fifth tourism france les recognized efforts restoring lebanon important sites candidate new wonders nature competition selected finalists cave selected nominees foundation announced new wonders nature list awards certificates include certificate recognition recycling campaign appreciation arab musical association best tourism project ministry tourism international environmental award german travel association names cave changed times discovery initially referred subsequently known finally river runs meaning water town cave entrance located transition occurred newspapers widely national symbol authorities issued stamp featuring lower promote national tourism shown stamp leads boat tours years stamp issued featured pound


pronounced keel massive located region northern chile west border alto national reserve central volcanic zone form ridge maximum height metres volcano embedded larger cluster known cluster cluster formed stages million years activity varying output including lava lava flows volcano proper formed units erupted million years ago ice ages principal complex cluster subject resulting formation cluster generated lava ranging composition main volcano exclusively composition systematic variations temperature crystal content recorded evolution cluster volcano activity deposits found summit mines lie complex altitude metres opened remained use world highest period originally obtained transported subsequently aerial employed transport town bring road network summit constructed impassable men reported living altitude metres making highest permanent residents earth geography geology regional setting central volcanic zone highly volcanic zone south_america generates rate cubic kilometres millennium cubic miles millennium tenth global average arc production lies kilometres zone arc migrated eastward high pacific_ocean coast arc contains compound generated cubic kilometres eruption products million years complex lies northwest volcanic complex local large province depth kilometres slow seismic velocity zone linked presence partial zone complex smaller duration activity location indicate complex long term output comparable output long term active central cases early peak output followed later lower volume activity cubic kilometres millennium cubic miles millennium followed cubic kilometres millennium cubic miles millennium japan mount peak california similar eruption histories decreases occur load imposed chambers increased travel distance local setting cluster located rio chile border sits platform rises metres main volcano composed east west kilometre long chain estimated volume cubic kilometres maximum slope summit area stage flow occurred northwestern volcano covered square kilometres run square kilometres volume cubic kilometres identified debris lack topography presence large juvenile blocks identify flow block flow lava dome flow originated dated lava flows summit areas dark grey colour extend far kilometres likely small lava summit northwest flank occupy flank north lies old ridge west lies east west ridge volcanic cluster contains generated cubic kilometres million years covering surface area square kilometres cluster surrounded northern western eastern sides salt flats deposits southern lies volcano cluster lies kilometre thick crust arid conditions preserved structures arranged north south northwestern indicate crust shallow underwent northwestward flank collapse generating debris deposit debris descended metres ran kilometres eventually covering area square kilometres flow volcano eroded lava dry rio valley favouring preservation slide deposit parts slide covered younger products indicating slide followed glacial episode slide lacks topography usually found debris radial ridges grooves landslide occurred stage eastern main volcano classic topography landslides covers length kilometres surface area square kilometres roughly half surface area mount surface area volume cubic kilometres assumed based probable thickness metres composition cluster ranges ranging appear lava flows form lava dome complexes rocks main volcano uniformly little evidence temporal variation composition potassium content ranges dominant component minor amounts subordinate components found evidence mixing rocks texture typically contain crystals generally crystals group million years crystal poor lack later contain crystals based data highest temperatures occurred phases high activity lower temperatures associated low output periods likely feedback increased deep influx mantle derived drive increased time eruption west flank output segregated peripheral volcano generating central generating parts main volcano subjected alteration stage subject alteration especially summit area lie rich deposits central complex heavily altered activity alteration driven formation deep reservoir resulting circulation rocks history eruption rates increased million years ago coinciding uniform composition onset strong alteration possible volcano feeding channels heat loss caused temperatures system increase activity waned million years ago included crystals drawn depths kilometres forming volcano proper million year duration activity volcanic complex systems comparable duration activity age lava flows ranges heavily flows eroded ones possibly lava flows tens thousands years old cluster cluster formed stages corresponding group group seven constructed formed constructed northern composite known garage dated lava northeastern cluster large breach southern crater likely product flank collapse deposit buried beneath younger material breach dated centres heavily eroded lie erupted unknown vent volume cubic kilometres vent location unknown composition dating distribution indicate association group poorly researched dome dated total volume group cubic kilometres indicating rate cubic kilometres millennium cubic miles millennium group erupted following probable million year hiatus located southern western parts cluster crater breached westwards exposing radial trace debris larger centres cluster associated lava field western dated negro lie southern cluster glacial cutting northeastern flanks reveal layers structure western located north group forms kilometres wide lava filled crater layers dip sits southwest negro ridge las lava field associated group vent locations unknown total volume group cubic kilometres indicating rate cubic kilometres millennium cubic miles millennium group dispersed including volcano largest group cluster includes volcano platform eastern deeply exposed materials heavily altered deeper sections lava fields west southwest western field associated lies east probably volcano past lava dome surrounded lava table forms northbound kilometre long ridge alteration affected western lateral terminal platform sits underneath main volcano lava flowed north southern metre table hill dated platform presumably forms total volume cluster originated ridge trend buried beneath lava dome short lava flows youngest group volcano total volume group cubic kilometres indicating rate cubic kilometres millennium cubic miles millennium main phases composition including formed proper main volcano formed stages bulk volcano formed stage lava flow southwest unusually long kilometres vent metres altitude fed second vent northern flank metres summit generated lava flows shorter ones long northwest stage large flow fronts metres high flows moderately altered little evidence explosive activity obscured glacial erosion total volume cubic kilometres indicating rate cubic kilometres millennium cubic miles millennium volcano probably isolated cone existence previous stage excluded second stage named lasted formed eastern slopes volcano vent metres summit stage usually thicker stage summit vent stage thick subject alteration oldest stage erupted unknown vent lack total volume cubic kilometres indicating rate cubic kilometres millennium cubic miles millennium flank collapse possibly triggered large earthquake occurred stage stage stage named westernmost summit principal vent stage metres time course activity defined previous stages occurred likely based potassium dating lava flows derived main vent kilometre long metres thicker previous stages native deposits stage generated flow lava dome collapse occurred indonesia total volume stage cubic kilometres indicating rate cubic kilometres millennium cubic miles millennium youngest stage known lasted centered stage lava flows stage originate kilometre long ridge includes highest summit crater northeast ridge fed north flows extend southwards kilometres vent exception south flow metres thick thin metres oldest flows compared length longer flow thinner flows stage weakly partially glacial deposits total volume cubic kilometres indicating rate cubic kilometres millennium cubic miles millennium volcano active low temperature visible short infrared data satellites activity observed volcano currently despite height climate valley originates foot rio river drains western northwestern sides volcano eastern drains salt pan northeastern southeastern valleys intermittently transport water volcanic cluster evidenced glacial elevations metres western heavily past stages mapped southern found modest polished floor stage stages southern slopes small found northeastern summit stage lava flow small lies south glacial deposits human activity mining metres altitude yielded ore opened julian subsequently established transported later aerial system finally trucks transported converted acid active reported mining activity mountain mines present west south main runs mining camp metres metres road leading dated impassable rock falls network roads leading metres copper found area appear formed deep copper formed temperatures extinct altitude notable highest world metres highest permanently inhabited area expedition international high altitude expedition found miners lived altitude metres town reached higher foot expedition found higher abandoned village metres existed miners refused live conclusion taken expedition metres highest altitude west reported miners permanently lived area small group men lived altitude metres iron reportedly spent years considered highest human inhabitants earth research performed miners indicates fully altitude higher people lower areas families born raised lower altitudes


types volcanic types volcanic lava ash volcanic bombs blocks gases expelled volcanic vent distinguished named famous type behavior observed exhibit characteristic type eruption period activity display entire sequence types series different types observed involve gas forward type volcanic eruption driven compression gas direct opposite process activity type eruption driven steam contact types exhibit release instead causing existing rock wide defining types weakest hawaiian submarine followed stronger types followed strongest called ultra defined mechanism vary strength important measure strength volcanic index order magnitude scale ranging types eruption mechanisms volcanic arise main mechanisms gas release causing thermal chilling contact water causing particles steam causing types terms activity explosive explosive characterized gas driven explosions characterized lava significant explosive eruption volcanic vary widely strength extreme hawaiian characterized lava fluid lava flows typically dangerous extreme large violent highly dangerous explosive events bound style frequently display different types passive explosive span single cycle vertically single crater near peak exhibit lateral notably hawaiian start rift zones strongest develop fracture zones scientists believed mixed chamber climbing upward process estimated thousands years columbia_university found eruption costa_rica volcano likely triggered took nonstop route mantle months volcano index volcanic index commonly shortened scale measuring strength institution global program assessing impact historic prehistoric lava flows operates way similar scale earthquakes interval value represents increasing magnitude vast majority volcanic volcanic index produce juvenile explosive gas release range intensity relatively small lava hawaii catastrophic ultra eruption columns high bigger eruption mount buried hawaiian hawaiian type volcanic eruption named hawaiian type hawaiian types volcanic events characterized eruption fluid type low content volume ejected material hawaiian half found types steady production small amounts lava builds large broad form shield volcano centralized main summit volcanic types occur summit center hawaiian begin line vent vent called curtain fire die lava begins concentrate central vent form large lava continuous sporadic reach heights hundreds meters particles lava usually cool air hitting ground resulting accumulation fragments air especially thick cool fast surrounding heat hit ground hot accumulation forms rates high form fed lava flows hawaiian extremely long lived cone continuously hawaiian volcanic feature formation active lava lakes self maintaining pools raw lava thin crust semi cooled rock currently lakes world vent flows hawaiian divided types structural characteristics lava relatively smooth lava flow sheet advancement toes lava column lava flows tend slower flows measure thick flows thick outside layers rubble like mass hot interior preventing cooling lava moves peculiar way flow pressure breaks general mass moves forward lava lava increasing increasing rate shear lava turns flow hawaiian responsible unique objects small volcanic particles carried formed wind chilling quickly shaped fragments known tears hawaiian volcano deity especially high winds form long drawn strands known hair lowest density rock type earth hawaiian named hawaii necessarily restricted largest lava fountain recorded formed island mount twice high mountain stands known hawaiian activity include parasitic cone located island continuously began based curtain fire january gave way centralized site east rift eventually building active cone list hawaii list hawaiian emperor chain mount italy mount type volcanic eruption named volcano continuously centuries driven gas bubbles gas bubbles accumulate large bubbles called gas grow large rise lava column reaching surface difference air pressure causes bubble burst loud pop throwing air way similar soap bubble high gas pressures associated continued activity generally form episodic explosive accompanied distinctive loud occur minutes term describe wide variety volcanic varying small volcanic large columns reality true characterized short lived explosive intermediate ejected high air columns measure hundreds meters height formed form relatively lava end product relative non damaging nature source vent allow continue thousands years makes dangerous types volcanic bombs fragments travel paths landing source vent steady accumulation small fragments builds composed completely form accumulation tends result ordered rings similar hawaiian differences produce sustained columns produce volcanic products associated hawaiian specifically tears hair produce fewer lava flows material tend form small known activity include mexico erupted years life activity began lava base primary mode activity ceased final height time scientists able observe complete life cycle volcano mount italy displayed activity recent example mount antarctica southernmost active volcano world having observed activity consists frequent activity namesake mild explosive activity possesses active historical time essentially continuous occasionally accompanied lava flows recorded millennium type volcanic eruption named volcano named following observations highly volcano difficult gases escape similar leads buildup high gas pressure eventually cap holding resulting explosive eruption unlike ejected lava fragments aerodynamic higher greater incorporation material broken cap explosive counterparts columns reaching high lastly deposits initial activity characterized series short lived explosions lasting minutes hours volcanic bombs blocks wear lava dome holding leading quiet continuous early sign future activity lava dome growth collapse generates material volcano slope deposits near source vent consist large volcanic blocks bombs called bread crust bombs especially common deeply cracked volcanic form exterior ejected lava quickly fine shell inside continues cool center fragment expands cracking exterior bulk deposits fine ash ash moderately dispersed abundance indicates high degree result high gas contents cases found result interaction water suggesting partially exhibited activity include japan site activity near continuously new_guinea volcano costa_rica exhibited activity eruption type volcanic eruption named volcano mount martinique site massive eruption worst natural disasters history large gas dust ash lava fragments blown volcano central crater driven collapse lava dome collapses create large columns early sign coming eruption growth called lava spine volcano summit total collapse material collapses forming fast moving flow known block ash flow moves mountain tremendous speeds hour massive landslides dangerous world capable tearing populated areas causing massive loss life eruption mount caused tremendous destruction killing people destroying town worst volcanic event 20th century characterized prominently flows drive mechanics eruption similar eruption volcano structure able withstand pressure eruption occurs large explosion smaller ones known activity include mount martinique eruption mount completely devastated island destroying town leaving survivors eruption directly preceded lava dome growth volcano philippines active volcano site different types included approximately summit provide pathways frequent flows mudslides violent eruption occurred responsible deaths eruption mount prior eruption peak recognized volcano people killed studying large type volcanic eruption named historical eruption mount mount buried roman towns specifically chronicler younger process starts chamber dissolved volatile gases stored gases accumulate rise bubbles reach certain size total volume explode narrow confines force gases associated forming column eruption velocity controlled gas contents column low strength surface rocks commonly crack pressure eruption forming outgoing structure pushes gases faster massive columns distinctive feature eruption reach atmosphere directly volcano driven internally gas expansion reaches higher air expands dense convection thermal expansion volcanic ash drive powerful prevailing winds drive direction away volcano highly explosive associated volatile rich occur typically hours days longer associated associated occur given chamber structure rich dioxide similar creating explosive events form sustained columns similar hawaiian lava types produce sustained eruption columns maintained growth bubbles speed surrounding regions affected subjected heavy affecting area size material ash eventually finds way ground covering landscape thick layer cubic kilometers ash dangerous feature flows generated material collapse mountain extreme speeds hour ability extend reach eruption hundreds kilometers hot material volcano summit ice deposits volcano mixes form fast moving mudslides consistency wet concrete speed river rapid major events include eruption mount buried roman towns layer ash model eruption mount erupted times eruption caused problems allied armies advanced italy report younger lead scientists refer eruption mount washington ripped apart volcano summit eruption volcanic index strongest types called ultra recent lake thousand years ago times material erupted mount iceland example eruption past years pattern violent initial followed prolonged lava lower volcano philippines june produced high eruption column released dioxide arise interactions water driven thermal opposed driven thermal expansion comes contact water temperature difference causes violent water lava interactions eruption products believed regular shape finer products differences mechanisms debate exact nature scientists believe fuel reactions critical explosive nature thermal fuel reactions fragment volcanic material stress waves widening cracks increasing surface area lead rapid cooling explosive driven eruption type volcanic eruption caused shallow water interactions water lava named famous example eruption formation island coast iceland wet equivalent ground based taking place explosive water heated lava flashes steam expands violently contact fine ash shallow water volcanic oceanic islands specifically confined happen land caused rising comes contact water bearing rock formation shallow levels volcano products generally occur albeit rarely like generally continuous rhythmic distinct defining feature eruption formation surge base surge ground radial cloud develops eruption column base caused collapse column overall regular volcanic column cloud nearest vent resulting wedge shape associated moving rings shaped rock left lateral movement occasionally disrupted bomb rock explosive eruption followed path ground wet spherical ash known common surge indicator time tend form broad low relief volcanic dug ground rings circular structures built rapidly lava structures associated single vent eruption arise fracture zones rift zone dug tend violent ones forming ring example eruption mount feature generated explosive deposition truly volcanic form lava cracks lava explodes steam explosion breaking rock apart volcano flank consecutive explosions type eventually generate cone known activity include iceland volcano built depth emerged atlantic_ocean coast iceland initial highly explosive volcano grew rising lava started interact water air finally activity waned character alaska azores examples water activity mount new_zealand erupted rift zone killing people mediterranean_sea breached sea level july source dispute sovereignty italy france great_britain volcano build strongly withstand erosion disappeared waves soon appeared underwater volcano breached sea level exhibited activity time site earlier eruption submarine submarine type volcanic eruption occurs underwater estimated total volcanic volume generated submarine near mid ocean ridges problems associated detecting deep sea remained virtually unknown advances 1990s possible observe submarine produce break surface form volcanic islands island chains submarine driven processes near plate boundaries mid ocean ridges built melting mantle rock rises portion convection cell surface associated zones driven plates add rising plate lowering melting point process generates different rock mid ocean ridge primarily flows explosive spreading rates mid ocean ridges vary widely year mid-atlantic ridge east pacific rise higher spreading rates probably cause higher levels technology studying exist technology possible listen acoustic waves known waves released submarine earthquakes associated submarine volcanic reason land based detect sea based earthquakes magnitude acoustic waves travel water long periods time system north pacific maintained united_states_navy originally intended detection submarines detected event average years common underwater flow lava circular lava flow named unusual shape common marginal sheet flows indicative larger scale flows rocks common shallow water environments plate movement starts carry away source eruption rates start die water erosion volcano final stages eruption caps flows world active stage life type volcanic eruption characterized interactions lava ice nature occurs areas high latitude high altitude suggested actively dump heat ice covering producing mix means generate dangerous floods study relatively new field early accounts described unusual flat topped steep sided called iceland suggested formed ice english language paper subject published william henry describing field northwest british_columbia canada process builds structures originally paper begins volcanic growth resemble occur deep sea forming piles lava base volcanic structure lava comes contact cold ice forming called ice finally lake explosive activity begins building flanks eventually lake continued lava flows lava slowly forming preserved stages example iceland products volcano ice interactions stand structures shape dependent complex environmental interactions glacial good indicator past ice distribution making important climatic marker ice ice worldwide concerns structures resulting mass landslides evidence volcanic glacial interactions evident iceland parts british_columbia possible play role products identified iceland canadian province british_columbia states hawaii alaska cascade range western north_america south_america planet mars known activity include tropical hawaii evidence past activity volcano form deposit summit originated years ago ice age summit covered ice british survey reported volcanic eruption antarctica ice sheet years ago believed biggest eruption antarctica years volcanic ash deposits volcano identified airborne radar survey buried later hudson mountains close pine island iceland known glaciers site example eruption ice cap occurred estimated ice search life mars scientists suggested red planet potential sites reviewed compared extensively similar features iceland viable communities found living deep pressures bar furthermore exist rocks altered volcanic glass conditions exist polar regions mars today occurred steam blast type eruption driven expansion steam cold ground surface water come contact hot rock explodes surrounding rock mixture steam water ash volcanic bombs volcanic blocks distinguishing feature explosions blast fragments pre existing solid rock volcanic new erupted driven cracking rock strata pressure activity result eruption rock face strong withstand explosive force outright occur cracks rock probably develop weaken future precursor future volcanic activity generally weak exceptions events triggered earthquake activity volcanic precursor travel lines form base volcanic block rain release deadly toxic gas able range eruption known exhibit activity include mount exhibited activity prior catastrophic eruption volcano philippines guadeloupe lesser antilles activity hills volcano west_indies volcano frequent like crater lake mount known sudden mount historical volcano including deadly eruption