ReferenceforTeachingI
TheGrandCanyonTheGrandCanyon(大峡谷)isconsideredoneofthesevenwondersofthenaturalworld
ItisoneofAmerica'smostfamousnationalparks
Visitorstothecanyoncomefromallpartsoftheworld
Officialssayabout5millionpeoplevisittheGrandCanyoneachyear
Thecanyonextends450kilometers
ButthesurroundingareadoesnotsuggesttheexistenceofsuchalargeopeningintheEarth
Visitorscomeuponthecanyonsuddenly,whentheyreachtheedge
Thentheyarelookingatalandlikenothingelseintheworld
Wallsofrockfallawaysharply
Insomeplaces,thecanyonwallsaremorethanakilometerdeep
Farbelowisthedark,turninglineoftheColoradoRiver(科罗拉多河)
Ontheothersideofthecanyon,sunshinelightsuptherockwallsinred,orangeandgold
Thebrightcolorsaretheresultofmineralsintherocks
Theirappearancechangeswiththelight,thetimeofyearsandtheweather