( ( Some scientists ) ( ( believe ( ( these mountains ) ( ( were once ) ( under ( ( great sheets ) ( of ice ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT Some) (NNS scientists)) (VP (VBP believe) (SBAR (S (NP (DT these) (NNS mountains)) (VP (VBD were) (ADVP (RB once)) (PP (IN under) (NP (NP (JJ great) (NNS sheets)) (PP (IN of) (NP (NN ice))))))))) (. .)))
Some scientists believe these mountains were once under great sheets of ice.
(ROOT (S (NP (NNS Scientists)) (VP (VBP know) (SBAR (IN that) (S (NP (DT some) (NNS mountains)) (VP (VBD were) (ADVP (RB once)) (PP (IN at) (NP (NP (DT the) (NN bottom)) (PP (IN of) (NP (DT an) (NN ocean))))) (SBAR (IN because) (S (NP (JJ marine) (NNS fossils)) (VP (VBP have) (VP (VBN been) (VP (VBN found) (PP (IN on) (NP (NP (DT the) (NNS peaks)) (PP (IN of) (NP (DT some) (NNS mountains)))))))))))))) (. .)))