▁are ▁known ▁for ▁Lake ▁Er ie , ▁Lake ▁Hur on , ▁and ▁Lake ▁Super ior . ▁A ▁very ▁large ▁sheet ▁of ▁water , ▁named ▁Lake ▁Ag ass iz , ▁once ▁o vers p read ▁a ▁broad ▁till ▁plain ▁in ▁northern ▁Minnesota ▁and ▁North ▁Dak ota . ▁The ▁out let ▁of ▁this ▁gla cial ▁lake , ▁called ▁river ▁Warren , ▁er oded ▁a ▁large ▁channel ▁in ▁which ▁the ▁Minnesota ▁River ▁evident ▁today . ▁The ▁Red ▁River ▁of ▁the ▁North ▁flows ▁north ward ▁through ▁a ▁plain ▁formerly ▁covered ▁by ▁Lake ▁Ag ass iz . ▁ ▁C ertain ▁extraordinary ▁features ▁were ▁produced ▁when ▁the ▁retre at ▁of ▁the ▁ice ▁sheet ▁had ▁progress ed ▁so ▁far ▁as ▁to ▁open ▁an ▁east ward ▁out let ▁for ▁the ▁marg inal ▁la kes . ▁This ▁out let ▁occurred ▁along ▁the ▁de pression ▁between ▁the ▁north ward ▁slope ▁of ▁the ▁App al ach ian ▁plate au ▁in ▁west - central ▁New ▁York ▁and ▁the ▁south ward ▁slope ▁of ▁the ▁mel ting ▁ice ▁sheet . ▁When ▁this ▁east ward ▁out let ▁came ▁to ▁be ▁lower ▁than ▁the ▁south - west ward ▁out let ▁across ▁the ▁height ▁of ▁land ▁to ▁the ▁Ohio ▁or ▁Mississippi ▁river , ▁the ▁dis charge ▁of ▁the ▁marg inal ▁la kes ▁was ▁changed ▁from ▁the ▁Mississippi ▁system ▁to ▁the ▁Hudson ▁system . ▁Many ▁well - defined ▁channels , ▁cutting ▁across ▁the ▁north - s lop ing ▁sp urs ▁of ▁the ▁plate au ▁in ▁the ▁neighborhood ▁of ▁Sy rac use , ▁New ▁York , ▁mark ▁the ▁temporary ▁paths ▁of ▁the