( ( ( ( The ( semi-circular recession ) ) , ) ( ( ( ( ( the ( outwash debris ) ) ( in ( the chasm ) ) ) , ) and ) ( ( the ( dendritic ( dried-up riverbeds ) ) ) ( leading ( to ( the edge ) ) ) ) ) ) ( ( suggest ( that ( ( ( ( ( a ( large waterfall ) ) , ) ( similar ( to ( ( ( ( the ( USA 's ) ) ( Niagara Falls ) ) or ) ( Angel ( Falls ( io Venezuela ) ) ) ) ) ) ) , ) ( was ( present ( in ( ( the ( planet 's ) ) ( distant past ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ semi-circular) (NN recession)) (, ,) (NP (NP (NP (DT the) (JJ outwash) (NN debris)) (PP (IN in) (NP (DT the) (NN chasm)))) (, ,) (CC and) (NP (NP (DT the) (JJ dendritic) (JJ dried-up) (NNS riverbeds)) (VP (VBG leading) (PP (TO to) (NP (DT the) (NN edge))))))) (VP (VBP suggest) (SBAR (IN that) (S (NP (NP (DT a) (JJ large) (NN waterfall)) (, ,) (ADJP (JJ similar) (PP (TO to) (NP (NP (NP (DT the) (NNP USA) (POS 's)) (NNP Niagara) (NNP Falls)) (CC or) (NP (NNP Angel) (NNP Falls) (NNP io) (NNP Venezuela))))) (, ,)) (VP (VBD was) (ADJP (JJ present) (PP (IN in) (NP (NP (DT the) (NN planet) (POS 's)) (JJ distant) (NN past)))))))) (. .)))
The semi-circular recession, the outwash debris in the chasm, and the dendritic dried-up riverbeds leading to the edge suggest that a large waterfall, similar to the USA's Niagara Falls or Angel Falls io Venezuela, was present in the planet's distant past.
(ROOT (S (NP (NNP Iguassu) (NNP falls)) (VP (VBZ is) (NP (NP (DT the) (JJS largest) (NN waterfall)) (PP (IN on) (NP (DT the) (NN planet))))) (. .)))