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2.MountainsHumanbeingsventureintothehighestpartsofourplanetattheirperil.Somemightthinkthatbyclimbingagreatmountaintheyhavesomehowconqueredit,butwecanonlybevisitorshere.Thisisafrozenalienworld.Thisistheotherextreme-oneofthelowesthottestplacesonEarth.It'soverahundredmetresbelowthelevelofthesea.Buthereamountainisingestation.Poolsofsulphuricacidareindicationsthatdeepundergroundtherearetitanicstirrings.ThisistheDanakilDepressioninEthiopia,lyingwithinacolossalrentoftheearth'ssurfacewheregiantlandmassesarepullingawayfromoneanother.Lavarisestothesurfacethroughthiscrackinthecrustcreatingachainofyoungvolcanoes.Thisone,ErtaAle,istodaythelongestcontinuallyeruptingvolcanoontheplanet,alakeoflavathathasbeenmoltenforoverahundredyears.ThesesamevolcanicforcesalsocreatedEthiopia'shighlands.70millionyearsagothislandwasjustasflatandasdeepastheDanakilDepression.Moltenlavarisingfromtheearth'scoreforcedupahugedomeofrock500mileswide,theroofofAfrica.Overmillennia,rainandicecarvedtherockintoalandscapeofspiresandcanyons.Thesesummits,nearly3milesup,arehometosomeveryremarkablemountaineersGeladababoons.TheyareuniquetothehighlandsofEthiopia.Thecliffswheretheysleepareforexpertclimbersonly,andGeladocertainlyhavetherightequipment.thestrongestfingersofanyprimateandanutterlyfearlessdisposition.Butyouneedmorethanaheadforheightstosurviveuphere.AdayinaGelado'sliferevealshowthey'verisentothechallenge.Forallmonkeysmorningisgroomingtime,achancetocatchupwithfriends.But,unlikeothermonkeys,Geladoschatterconstantlywhiletheydoit.It'sagreatwaytonetworkwhileyourhandsarebusy.Butthesesocialscan'tgoonfortoolong.Geladoshaveabusydailyscheduleandthere'sworktobedone.Mostmonkeyscouldn'tliveuphere.There'snofoodandfewinsectstofeedon.ButGeladosareuniquethey'retheonlymonkeysintheworldthatlivealmostentirelyongrass.Theyliveinthelargestassembliesformedbyanymonkeys.Somegroupsare800strongandtheycropthehighmeadowslikeherdsofwildebeest.TheGeladosgrazealongsideWaliaibex,whicharealsouniquetothesehighlands.TheserarecreaturesareusuallyveryshybuttheydroptheirguardwhentheGeladosarearound.Youmightexpectthatgrazerswouldavoideachother'spatchbutthisisaspecialalliancefromwhichbothpartnersbenefit.It'snotsoriskytoputyourheaddownifothersareonthelookout.Ethiopianwolves-theywon'tattemptanattackinbroaddaylight.Butatdusktheplateaubecomesamoredangerousplace.Withthegrazinglargelyoverthere'salastchancetosocialisebeforereturningtothesleepingcliffs.Anearlywarningsystemputseveryoneonthealert.Theirdayendsasitbegan,safeonthesteepcliffs.TheEthiopianvolcanoesaredormant,butelsewhereothersstillrage.Volcanoesformthebackboneofthelongestmountainchainonourplanet-theAndesofSouthAmerica.Thisvastrangestretches5,000milesfromtheEquatordowntotheAntarctic.ItformedasthefloorofthePacificOceanslidbeneaththeSouthAmericancontinent,bucklingitsedge.AtthesouthernendstandthemountainsofPatagonia.It'shighsummer,buttheAndeshavethemostunstablemountainweatherontheplanetandstormscaneruptwithoutwarning.Temperaturesplummetandguanacosandtheirnewbornyoungmustsuddenlyendureablizzard.Truly,allseasonsinoneday...Apuma-thelionoftheAndes.Pumasareusuallysolitaryandsecretive.Toseeagroupwalkingboldlyintheopenisextremelyrare.It'safamily-amotherwithfourcubs.Shehasjustonebriefsummerinwhichtoteachthemtheirmountainsurvivaltechniques.Rearingfourcubstothisageisanexceptionalfeat,butshedoeshaveanexcellentterritory,richinfoodandwater.Althoughthecubsarenowaslargeastheirmother,theystillrelyonherfortheirfood.Itwillbeanotheryearbeforethecubscanhuntforthemselves.Withouttheirmother'sskillandexperiencetheywouldneversurvivetheirfirstwinter.Batteredbyhurricaneforcewinds,theseslopesarenowlifeless.Furthernorth,theyholdotherdangers.Movingat250milesanhour,anavalanchedestroyseverythinginitspath.IntheAmericanRockiesa100,000avalanchesdevastatetheslopeseverywinter.ThishugemountainchaincontinuesthegreatspinethatrunsfromPatagoniatoAlaska.TheslopesoftheRockies,bleakthoughtheyare,provideawinterrefugeforsomeanimals.Amothergrizzlyemergesfromherdenaftersixmonths'dozingunderground.Hertwocubsfollowherandtaketheirfirststepsintheoutsideworld.Thesesteepslopesprovideasanctuaryforthecubs.Amalebearwouldkillandeatthemgiventhechance.Butbiganimalsfinditdifficulttogetabouthere.Malesmaybetwicethesizeofafemaleandevenshecanhaveproblems.Hercubs,however,makelightofthesnowandoflifeingeneral.Butthemotherfacesadilemma:it'ssixmonthssinceshelastfedandhermilkisstartingtorundry.Shemustsoonleavethesafetyofthesenurseryslopesandleadhercubsawayfromthemountain.Ifshedelays,thewholefamilywillriskstarvation.SummerrevealsthetruenatureoftheRockies.Strippedofsnow,thepeaksbeartheirsculptedforms.Onlynowcanmountaineersreclaimtheupperreaches.Twomilesupthecrumblingprecipicesseemdevoidoflife.Butthereareanimalshere-agrizzlybear.Itseemstobeanoddcreaturetofindonthesehighrockyslopes.It'shardtoimaginewhatcouldhaveattractedithere.Atthistimeoftheyearbearsshouldbefatteningupforthewinter.Yettheygatherinsomenumbersontheseapparentlybarrenslopes.They'researchingforaratherunusualfood-moths.Millionshaveflownupheretoescapetheheato