1thE DominAnt FEAturE on thE mAp oFCAnADA is thE two-million-squArE-milE mAss oF AnCiEnt roCk known As thECAnADiAn shiEl
D、thE shiElD swEEps in A grEAt ArC ArounD huDsonBAy From FAr northwEst to FAr northEAst, touChing thE grEAt lAkEs on thE south AnD ExtEnDing EAstwArD DEEp into quEBEC、thE roCk oF thE shiElD Consists mAinly oF grAnitE AnD gnEiss FormED nEArly Four Billion yEArs Ago.During thE iCE AgEs, hugE glACiErs ADvAnCED AnD rEtrEAtED ovEr thE rEgion, sCouring thE surFACE, rEmoving most oF thE Existing soil, AnD hollowing out CountlEss lAkEs.
2 ClAy soils Exist in A FEw ArEAs on thE shiElD’s southErn EDgE, But AttEmpts to Bring thEm into AgriCulturAl usE hAvE BEEn lArgEly unsuCCEssFul. howEvEr, thE rEgion’s minErAl wEAlth hAs sustAinED Both tEmporAry AnD pErmAnEnt sEttlEmEnts During thE pAst CEntury, AnD morE rECEntly, somE oF its vAst potEntiAl For hyDroElECtriC powEr hAs BEEn tAppE
D、
thE worD sCouring in pArAgrAph 1 is ClosEst in mEAning toA．FrEEzing
B．upliFting
C．improving
D、sCrAping