Why is it that numerous scriptures in Revelation speak in 3's (sea, air, earth / trees, vegetation, grass/ etc.) and in each instance the 3 parts each mean something. Why has the author now decided to break his M.O. and have these 3 parts just mean complete destruction??
Actually, the scenario is definitely not one involving "complete destruction". The destruction from the seven plagues (which is exegetically based on the ten plagues of Egypt in Exodus, cf. the affliction of festering sores in v. 2, turning water to blood in v. 3-4, darkness in v. 8, frogs in v. 13, hail in v. 21, drying up the waters in v. 12-13) in ch. 15-16 is necessarily incomplete because its purpose is to torture the peoples into repentance (cf. especially v. 9, 11, 21). It is in the parallel vision of the seven trumpets in ch. 8-11 where the fraction of one-third is especially prominent and stereotyped. This vision is also based on motifs of the ten plagues of Egypt, and the seven woes again are intended to represent incomplete destruction: "A third of humanity was killed by these three plagues ... the rest of humanity, those not killed by these plagues, did not repent of the products of their own manufacture, that is, they did not cease to worship the demons, or idols made of gold and silver and bronze and stone and wood" (9:18-20). The fraction of one-third is probably used because it implies that the majority of mankind survives the plague, to be tormented at a later time by another series of plagues, and then finally to be destroyed at the end of the world. In other words, the apocalypse is written in a way that implies that God would give mankind many opportunities to repent from their idolatry (e.g. the seven seals in ch. 6-7, the seven trumpets in ch. 8-11, the seven bowls of ch. 15-16) before he finally destroys them all in ch. 19.