( ( The ( rock material ) ) ( ( may ( be ( loosened ( by ( ( earthquakes , ) ( ( rain , ) ( ( ( ( ( plant-root wedging ) , ) ( expanding ice ) ) , ) ( among ( other things ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN rock) (NN material)) (VP (MD may) (VP (VB be) (VP (VBN loosened) (PP (IN by) (NP (NP (NNS earthquakes)) (, ,) (NP (NP (NN rain)) (, ,) (NP (NP (JJ plant-root) (NN wedging)) (, ,) (NP (VBG expanding) (NN ice)) (, ,) (PP (IN among) (NP (JJ other) (NNS things)))))))))) (. .)))
The rock material may be loosened by earthquakes, rain, plant-root wedging, expanding ice, among other things.
(ROOT (S (NP (NN Ice) (NN wedging)) (VP (VBZ occurs) (SBAR (IN because) (S (NP (NN water)) (VP (VBZ expands))))) (. .)))