The sinking I very much doubt was at the control of the Valar.
Three such mass continental movements have happened 3 times in the First Age. Once when Melkor destroyed the Two Pillars of Light (the world then split into 3 continents and Aman was formed), once after the Fall of Utumno and the War of the Powers (a new continent was formed between Middle-earth and the Lands of Sun called the Dark land), and once after the War of Wrath. None of these were at the control of the Valar. They certainly did not want there lovely Isle of Almaren ruled after the first great battle.
Ps: If you want to have a look at some maps then give us a shout and I will pm you with the links.