Earth Won't Have Five Oceans Forever (The Sixth Is Already Forming)

In terms of sheer area, oceans are top of the list of the most common landforms. Yes, even oceans are landforms, given that they are composed of vast basins riddled with trenches and mountains. In the strictest sense, there is only one ocean — the global ocean — which covers roughly 71% of the Earth's surface; however, we humans, for a combination of geological, political, and navigation reasons, have divided it into fragments.

There are currently five recognized oceans on Earth: the Pacific, Atlantic, Indian, Arctic, and Antarctic Oceans. The Antarctic Ocean, also known as the Southern Ocean, was the most recent one to gain recognition, having been defined by the International Hydrographic Organization in 2000. Now, a sixth ocean is on the way, but this time, it's not simply a matter of cartographic borders.

Earth's new ocean is being formed by tectonic activity. On the Somali peninsula, three tectonic plates meet in a region known as the Afar Triangle. The Nubian plate, comprising most of the African continent; the Somali plate, comprising easternmost Africa; and the Arabian plate, comprising the Arabian peninsula, all come together in a hotspot of seismic activity. For millions of years, these three plates have been drifting apart from one another, and eventually, they will rip the African continent in two. As the continents drift further apart, the space between will flood with water from the Red Sea and Gulf of Aden, forming a sixth ocean. That process won't be complete for another five to ten million years, but the signs are already appearing.

Along the fault lines between the Nubian, Somali, and Arabian plates, signs of a nascent ocean are already apparent. The clearest evidence of this is the East African Rift System (EARS), which runs from the Red Sea down to Mozambique. Here, the Nubian and Somali plates, which were once united, are slowly separating from each other, creating the Great Rift Valley. The ribbon lakes of East Africa include Lake Nyasa and Lake Tanganyika, the latter of which is the longest and second-deepest freshwater lake in the world. These lakes will slowly widen as the tectonic plates shift, ultimately becoming part of the sixth ocean.

Perhaps the most dramatic evidence of a newly-forming ocean came in 2005, when the Dabbahu volcano in the Afar region erupted and tore a 35-mile-long rift through the Ethiopian desert. The Dabbahu Fissure, as it's now known, is evidence of a divergent boundary, where two tectonic plates are separating (the opposite is a convergent boundary). This is exactly what happened when the supercontinent of Pangea broke apart 200 million years ago, forming the Atlantic and Indian Oceans, and it was only a matter of time (a lot of it) before we started to get another.