( ( The waterfall ) ( ( flows ( through ( ( a ( rock dike ) ) ( left ( by ( a ( retreating glacier ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN waterfall)) (VP (VBZ flows) (PP (IN through) (NP (NP (DT a) (NN rock) (NN dike)) (VP (VBN left) (PP (IN by) (NP (DT a) (VBG retreating) (NN glacier))))))) (. .)))
The waterfall flows through a rock dike left by a retreating glacier.
(ROOT (S (NP (DT A) (NN glacier)) (VP (VBZ leaves) (PP (IN behind) (NP (JJ bare) (NN rock))) (SBAR (WHADVP (WRB when)) (S (NP (PRP it)) (VP (VBZ retreats))))) (. .)))
A glacier leaves behind bare rock when it retreats.