Once the Pacific and Atlantic oceans were separated by a giant landmass, but then a chink formed in the supercontinent and the waters merged. According to new fossil dating this happened about 41 million years ago, million of years earlier than some scientists had estimated.
The southern supercontinent, Gondwana, which once included land from most of the continents in the Southern Hemisphere, started to break up about 160 million years ago due to the same forces that drive plate tectonics.
During this breakup, an oceanic passageway, called the Drake Passage, formed between the Antarctic Peninsula and South America. This opening connects the Pacific and Atlantic oceans and encircles Antarctica in a ring of cool water known as the Antarctic Circumpolar Current (ACC).