ada ▁de ▁Cha ig ü ire ▁valley ▁origin ates ▁at ▁the ▁foot ▁of ▁A uc an qu il cha . ▁The ▁Rio ▁Lo a ▁river ▁dra ins ▁the ▁western ▁and ▁north western ▁sides ▁of ▁the ▁vol cano ; ▁the ▁eastern ▁side ▁dra ins ▁into ▁the ▁Sal ar ▁de ▁O ll ag ü e ▁salt ▁pan , ▁the ▁n ort he astern ▁into ▁the ▁Sal ar ▁de ▁L agu ani , ▁and ▁the ▁sout he astern ▁into ▁the ▁Sal ar ▁de ▁Car c ote . ▁Most ▁valle ys ▁only ▁inter mitt ently ▁transport ▁water , ▁if ▁at ▁all , ▁but ▁it ▁forms ▁the ▁head w aters ▁of ▁the ▁Rio ▁Lo a . ▁ ▁The ▁vol can ic ▁cluster ▁was ▁mod est ly ▁gla ci ated ▁during ▁the ▁Qu atern ary , ▁as ▁ev iden ced ▁by ▁gla cial ▁stri ations ▁and ▁mor aines ▁at ▁elev ations ▁above ▁, ▁and ▁shows ▁evidence ▁of ▁gla ci ers ▁both ▁on ▁the ▁main ▁vol cano ▁and ▁its ▁subs idi aries . ▁At ▁least ▁two ▁distinct ▁gla cier ▁stages ▁took ▁place . ▁The ▁western ▁Az uf rera ▁ed ifice ▁was ▁heavily ▁gla ci ated ▁in ▁the ▁past . ▁At ▁least ▁three ▁m ora ine ▁stages ▁have ▁been ▁mapped ▁on ▁that ▁ed ifice , ▁and ▁on ▁its ▁southern ▁side ▁is ▁found ▁a ▁mod est ▁cir que ▁with ▁gla cially ▁pol ished ▁la vas ▁on ▁the ▁floor . ▁The ▁Rod ado ▁stage ▁ed ifice ▁has ▁several ▁m ora ine ▁stages ▁on ▁its ▁southern ▁s lop es . ▁Another ▁small ▁cir que