▁valley ▁was ▁greatly ▁deep ened ▁by ▁gla cial ▁action ▁during ▁the ▁Ice ▁age . ▁ ▁The ▁original ▁flow ▁is ▁thought ▁to ▁have ▁been ▁west ward ▁beginning ▁from ▁the ▁Laurent ian ▁shield ▁in ▁the ▁present ▁area ▁of ▁the ▁St . ▁Lawrence ▁River ▁to ▁eventually ▁join ▁the ▁Mississippi ▁River ▁d rain age ▁system . ▁ ▁During ▁contin ental ▁gla ci ation , ▁the ▁trem end ous ▁weight ▁of ▁the ▁gla cier ▁de pressed ▁the ▁area ▁of ▁the ▁St . ▁Lawrence ▁so ▁much ▁that ▁a ▁lower ▁point ▁of ▁d rain age ▁was ▁established ▁east ward ▁through ▁the ▁present ▁river ▁system . ▁The ▁area ▁is ▁still ▁re bound ing , ▁however , ▁and ▁the ▁rise ▁could ▁further ▁rear range ▁d rain age ▁within ▁ge olog ic ▁time ▁by ▁raising ▁the ▁out let ▁of ▁Lake ▁Ontario ▁sufficient ▁for ▁it ▁to ▁d rain ▁at ▁some ▁other , ▁lower ▁point . ▁ ▁See ▁also ▁ ▁Laurent ian ▁River ▁System ▁( O nt ario ) ▁Category : Form er ▁rivers <0x0A> </s> ▁Roman cing ▁Mary ▁Jane : ▁A ▁Year ▁in ▁the ▁Life ▁of ▁a ▁Failed ▁Mar iju ana ▁Gro wer ▁ ▁is ▁a ▁non - f iction ▁book , ▁written ▁by ▁Canadian ▁writer ▁Michael ▁Po ole , ▁first ▁published ▁in ▁ 1 9 9 8 ▁by ▁Gre yst one ▁Books . ▁In ▁the ▁book , ▁the ▁author ▁chron icles ▁the ▁reg rett able ▁consequences ▁of ▁his ▁decision ▁to ▁cultiv ate ▁mar iju ana ▁on ▁a ▁commercial ▁level . ▁Good read s ▁called ▁the ▁book , ▁an ▁" eng aging ▁bl end