( Iceland ( ( ( sits ( ( astride ( the ( Mid-Atlantic Ridge ) ) ) , ) ) ( part ( of ( ( the ( world-circling ( undersea ( mountain system ) ) ) ) ( that ( is ( ( the locus ) ( of ( new ( crust formation ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Iceland)) (VP (VBZ sits) (PRN (PP (IN astride) (NP (DT the) (NNP Mid-Atlantic) (NNP Ridge))) (, ,)) (NP (NP (NN part)) (PP (IN of) (NP (NP (DT the) (JJ world-circling) (NN undersea) (NN mountain) (NN system)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (NP (NP (DT the) (NNS locus)) (PP (IN of) (NP (JJ new) (NN crust) (NN formation))))))))))) (. .)))
Iceland sits astride the Mid-Atlantic Ridge, part of the world-circling undersea mountain system that is the locus of new crust formation.
(ROOT (S (NP (NNP Iceland)) (VP (VBZ sits) (PP (IN on) (NP (DT the) (JJ mid-atlantic) (NN ridge)))) (. .)))