( ( b -RRB- ) ( Crater ( ( lakes ( ( These ( volcanic lakes ) ) ( were ( formed ( when ( ( ( the ( bowl-shaped depressions ) ) ( around ( ( the orifices ) ( of volcanoes ) ) ) ) ( were ( ( filled ( with water ) ) ( after ( the eruptions ) ) ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (LST (LS b) (-RRB- -RRB-)) (NP (NNP Crater)) (VP (VBD lakes) (SBAR (S (NP (DT These) (JJ volcanic) (NNS lakes)) (VP (VBD were) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (JJ bowl-shaped) (NN depressions)) (PP (IN around) (NP (NP (DT the) (NNS orifices)) (PP (IN of) (NP (NNS volcanoes)))))) (VP (VBD were) (VP (VBN filled) (PP (IN with) (NP (NN water))) (PP (IN after) (NP (DT the) (NNS eruptions)))))))))))) (. .)))
b)Crater lakes These volcanic lakes were formed when the bowl-shaped depressions around the orifices of volcanoes were filled with water after the eruptions.
(ROOT (S (NP (NNS Craters) (CC and) (NNS rifts)) (VP (VBP become) (NP (NNS lakes)) (SBAR (WHADVP (WRB when)) (S (NP (PRP they)) (VP (VBP fill) (PP (IN with) (NP (NN water))))))) (. .)))