( There ( ( ( is also ) ( ( an ( 11-year ( sunspot cycle ) ) ) ( where ( ( ( the amount ) ( of ( sunspots ( visible ( on ( the sun ) ) ) ) ) ) varies ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBZ is) (ADVP (RB also)) (NP (NP (DT an) (JJ 11-year) (NN sunspot) (NN cycle)) (SBAR (WHADVP (WRB where)) (S (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NNS sunspots)) (ADJP (JJ visible) (PP (IN on) (NP (DT the) (NN sun))))))) (VP (VBZ varies)))))) (. .)))
There is also an 11-year sunspot cycle where the amount of sunspots visible on the sun varies.
(ROOT (S (NP (NNS Sunspots)) (VP (VBP occur) (PP (IN in) (NP (DT a) (CD 11) (NN year) (NN cycle)))) (. .)))