Suppose earth's landmasses someday all move together again. describe the changes that would occur in earth's oceans and earth's landmasses

It depends the speed of the collision. The higher the speed, the more impact it'll have on the landmass, perhaps forming more mountains. Now, on the landmass, life will struggle at first (depend on location or area where the land mass is at the equator) but will later eventually survive. The climate may be warmer or cooler than usual. On the oceans, damages may occur during the collision. The way certain sea creatures migrate and where schools go, will drastically change directions, changing the long tradition and cycle that it has been going on, and will also change the food cycle, locations where to live, hide, hunt and more.