Plate tectonics...

Opening of an ocean can be explain by plate tectonic. This theory of plate tectonic is an evolution of continent, ocean basin, mountain and continental margin.It consist of two processes, first continental drift state a supercontinent called pangea breaking apart about two million years ago.it can be proven by some evidence such as corellation of mountain belt and fossil. Second is sea floor spreading state that new ocean basin form from volcanism that happen in the ocean.