▁ ▁Ge ology ▁The ▁Al pine ▁L akes ▁W ilder ness ▁features ▁some ▁of ▁the ▁most ▁rug ged ▁top ography ▁in ▁the ▁Cas cade ▁Range ▁with ▁c rag gy ▁pe aks ▁and ▁rid ges , ▁deep ▁gla cial ▁valle ys , ▁and ▁gran ite ▁walls ▁sp otted ▁with ▁over ▁ 7 0 0 ▁mountain ▁la kes . ▁ ▁Ge ological ▁events ▁occurr ing ▁many ▁years ▁ago ▁created ▁the ▁diverse ▁top ography ▁and ▁dr astic ▁elev ation ▁changes ▁over ▁the ▁Cas cade ▁Range ▁leading ▁to ▁the ▁various ▁climate ▁differences . ▁ ▁The ▁history ▁of ▁the ▁formation ▁of ▁the ▁Cas cade ▁Mountains ▁dates ▁back ▁millions ▁of ▁years ▁ago ▁to ▁the ▁late ▁E oc ene ▁E po ch . ▁With ▁the ▁North ▁American ▁Pl ate ▁overrid ing ▁the ▁Pacific ▁Pl ate , ▁episodes ▁of ▁vol can ic ▁ igne ous ▁activity ▁pers isted . ▁ ▁In ▁addition , ▁small ▁fragments ▁of ▁the ▁ocean ic ▁and ▁contin ental ▁l ith os phere ▁called ▁ter ran es ▁created ▁the ▁North ▁C asc ades ▁about ▁ 5 0 ▁million ▁years ▁ago . ▁ ▁During ▁the ▁Ple ist oc ene ▁period ▁d ating ▁back ▁over ▁two ▁million ▁years ▁ago , ▁gla ci ation ▁adv ancing ▁and ▁retre ating ▁repeatedly ▁sc oured ▁the ▁landscape ▁leaving ▁ ▁depos its ▁of ▁rock ▁de br is . ▁The ▁last ▁gla cial ▁retre at ▁in ▁the ▁Al pine ▁L akes ▁area ▁began ▁about ▁ 1 4 , 0 0 0 ▁years ▁ago ▁and ▁was ▁north ▁of ▁the ▁Canada – US ▁border ▁by ▁ 1 0