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1、智课网托福备考资料托福阅读――地质地貌类（七）Earth'sinternalheat,fueledbyradioactivity,providestheenergyforplatetectonicsandcontinentaldrift,mountainbuilding,andearthquakes.Itcanalsobeharnessedtodriveelectricgeneratorsandheathomes.Geothermalenergybecomesavailableinapracticalformwhenundergroundheatistransferredbywat
2、erthatisheatedasitpassesthroughasubsurfaceregionofhotrocks(aheatreservoir)thatmaybehundredsorthousandsoffeetdeep.Thewaterisusuallynaturallyoccurringgroundwaterthatseepsdownalongfracturesintherock;lesstypically,thewaterisartificiallyintroducedbybeingpumpeddownfromthesurface.Thewaterisbroughttot
3、hesurface,asaliquidorsteam,throughholesdrilledforthepurpose.Byfarthemostabundantformofgeothermalenergyoccursattherelativelylowtemperaturesof80°to180°centigrade.Watercirculatedthroughheatreservoirsinthistemperaturerangeisabletoextractenoughheattowarmresidential,commercial,andindustrialspaces.Mo
4、rethan20,000apartmentsinFrancearenowheatedbywarmundergroundwaterdrawnfromaheatreservoirinageologicstructurenearPariscalledtheParisBasin.IcelandsitsonavolcanicstructureknownastheMid-AtlanticRidge.Reykjavik,thecapitalofIceland,isentirelyheatedbygeothermalenergyderivedfromvolcanicheat.Geothermalr
5、eservoirswithtemperaturesabove180°centigradeareusefulforgeneratingelectricity.Theyoccurprimarilyinregionsofrecentvolcanicactivityashot,dryrock;naturalhotwater;ornaturalsteam.Thelattertwosourcesarelimitedtothosefewareaswheresurfacewaterseepsdownthroughundergroundfaultsorfracturestoreachdeeprock
6、sheatedbytherecentactivityofmoltenrockmaterial.Theworld'slargestsupplyofnaturalsteamoccursatTheGeysers,120kilometersnorthofSanFrancisco,California.Inthe1990senoughelectricitytomeetabouthalftheneedsofSanFranciscowasbeinggeneratedthere.Thisfacilitywastheninitsthirddecadeofproductionandwasbeginni
7、ngtoshowsignsofdecline,perhapsbecauseofoverdevelopment.Bythelate1990ssome70geothermalelectric-generatingplantswereinoperationinCalifornia,Utah,Nevada,andHawaii,generatingenoughpowertosupplyaboutamillionpeople.Eighteencountriesnowgenerat
