( ( ( The particles ) ( in ( ( the cloud ) become ) ) ) ( ( ( ( ( attracted ( to ( each other ) ) ) ( with ( their ( own gravity ) ) ) ) and ) ( start ( to ( move ( towards ( each other ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NNS particles)) (PP (IN in) (NP (NP (DT the) (NN cloud)) (VP (VBN become))))) (VP (VP (VBD attracted) (PP (TO to) (NP (DT each) (JJ other))) (PP (IN with) (NP (PRP$ their) (JJ own) (NN gravity)))) (CC and) (VP (VBP start) (S (VP (TO to) (VP (VB move) (PP (IN towards) (NP (DT each) (JJ other)))))))) (. .)))
The particles in the cloud become attracted to each other with their own gravity and start to move towards each other.
(ROOT (S (NP (NNP Gravity)) (VP (VBZ makes) (SBAR (S (NP (NN soil) (CC and) (NN rock) (NNS particles)) (VP (VBP move) (ADVP (RB gradually)) (ADVP (RB down) (NP (DT the) (NN slope)) (PP (IN during) (NP (DT each) (NN thaw)))))))) (. .)))