( ( Gamma radiation ) ( ( ( ( ( is ( ( generated ( by ( ( radioactivity , ) ( ( the decay ) ( of ( radioactive ( ( -LRB- ( unstable -RRB- ) ) atoms ) ) ) ) ) ) ) ( both ( ( ( in ( ( Earth 's ) crust ) ) and ) ( in ( the atmosphere ) ) ) ) ) ) , ) and ) ( ( in reactions ) ( ( ( ( caused ( by ( cosmic ( ray collisions ) ) ) ) ( with ( atmospheric constituents ) ) ) , ) ( ( as ( well as ) ) ( by ( ( the decay ) ( of ( ( elementary particles ) ( produced ( by ( these collisions ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Gamma) (NN radiation)) (VP (VP (VBZ is) (VP (VBN generated) (PP (IN by) (NP (NP (NN radioactivity)) (, ,) (NP (NP (DT the) (NN decay)) (PP (IN of) (NP (JJ radioactive) (PRN (-LRB- -LRB-) (ADJP (JJ unstable)) (-RRB- -RRB-)) (NNS atoms)))))) (PP (DT both) (PP (IN in) (NP (NP (NNP Earth) (POS 's)) (NN crust))) (CC and) (PP (IN in) (NP (DT the) (NN atmosphere)))))) (, ,) (CC and) (VP (PP (IN in) (NP (NNS reactions))) (VBD caused) (PP (IN by) (NP (JJ cosmic) (NN ray) (NNS collisions))) (PP (IN with) (NP (JJ atmospheric) (NNS constituents))) (, ,) (PP (CONJP (RB as) (RB well) (IN as)) (IN by) (NP (NP (DT the) (NN decay)) (PP (IN of) (NP (NP (JJ elementary) (NNS particles)) (VP (VBN produced) (PP (IN by) (NP (DT these) (NNS collisions)))))))))) (. .)))
Gamma radiation is generated by radioactivity, the decay of radioactive (unstable) atoms both in Earth's crust and in the atmosphere, and in reactions caused by cosmic ray collisions with atmospheric constituents, as well as by the decay of elementary particles produced by these collisions.
(ROOT (S (NP (NP (JJ Radioactive) (NNS atoms)) (, ,) (NP (JJ nuclear) (NNS explosions)) (, ,) (CC and) (NP (NNS stars))) (VP (VBP produce) (NP (NN gamma) (NNS rays)))))
Radioactive atoms, nuclear explosions, and stars produce gamma rays