( ( ( ( ( ( The ( ( most obvious ) feature ) ) ( is ( a volcano ) ) ) , ) but ) ( ( the surface ) ( ( could also ) ( be ( ( fractured or ) ( faulted ( -LRB- ( ( ( a fault ) ( is ( ( a fracture ) ( where ( ( the rocks ) ( have ( ( ( moved ( on ( either side ) ) ) , ) ( causing earthquakes ) ) ) ) ) ) ) ) -RRB- ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT The) (ADJP (RBS most) (JJ obvious)) (NN feature)) (VP (VBZ is) (NP (DT a) (NN volcano)))) (, ,) (CC but) (S (NP (DT the) (NN surface)) (VP (MD could) (ADVP (RB also)) (VP (VB be) (UCP (ADJP (VBN fractured)) (CC or) (VP (VBN faulted) (PRN (-LRB- -LRB-) (S (NP (DT a) (NN fault)) (VP (VBZ is) (NP (NP (DT a) (NN fracture)) (SBAR (WHADVP (WRB where)) (S (NP (DT the) (NNS rocks)) (VP (VBP have) (VP (VBN moved) (PP (IN on) (NP (DT either) (NN side))) (, ,) (S (VP (VBG causing) (NP (NNS earthquakes))))))))))) (-RRB- -RRB-))))))) (. .)))
The most obvious feature is a volcano, but the surface could also be fractured or faulted (a fault is a fracture where the rocks have moved on either side, causing earthquakes).
(ROOT (S (NP (DT A) (NN fault)) (VP (VBZ is) (NP (NP (DT the) (NN fracture)) (VP (VBN caused) (SBAR (WHADVP (WRB when)) (S (NP (NP (NNS rocks)) (PP (IN on) (NP (DT both) (NNS sides)))) (VP (VBP move))))))) (. .)))