( ( ( ( Hot plumes ) ( of ( ( material rise ) ( towards ( ( ( the surface ) , ) ( cool ( by ( convecting ( with mantle ) ) ) ) ) ) ) ) ) ( -LRB- ( ( causing volcanoes ) -RRB- ) ) ) ( then ( ( plunge ( back down ) ) . ) ) )
(ROOT (S (NP (NP (JJ Hot) (NNS plumes)) (PP (IN of) (NP (NP (NN material) (NN rise)) (PP (IN towards) (NP (NP (DT the) (NN surface)) (, ,) (ADJP (JJ cool) (PP (IN by) (S (VP (VBG convecting) (PP (IN with) (NP (NN mantle))))))))))) (PRN (-LRB- -LRB-) (VP (VBG causing) (NP (NNS volcanoes))) (-RRB- -RRB-))) (ADVP (RB then)) (VP (VBP plunge) (ADVP (RB back) (RB down))) (. .)))
Hot plumes of material rise towards the surface, cool by convecting with mantle ( causing volcanoes ) then plunge back down.
(ROOT (S (NP (NNS Rises)) (ADVP (RB then)) (VP (ADVP (RB sinks)) (VBZ does) (NP (NP (JJR deeper) (NN material) (NN cause) (NN convection)) (PP (IN in) (NP (DT the) (NN mantle))))) (. .)))