The 800 km (500 miles) wide passage between Cape Horn and Greenwich Island is the shortest crossing from Antarctica to the rest of the world's land. The boundary between the Atlantic and Pacific Oceans is sometimes taken to be a line drawn from Cape Horn to Snow Island (130 km (80 miles) north of mainland Antarctica). Alternatively the meridian that passes through Cape Horn may be taken as the boundary. Both boundaries lie entirely within the Drake Passage.
The other two passages around Cape Horn, Magellan Strait and Beagle Channel, are very narrow, leaving little room for a ship, particularly a sailing ship, to maneuver. They can also become icebound, and sometimes the wind blows so strongly no sailing vessel can make headway against it. Hence most sailing ships preferred the Drake Passage, which is open water for hundreds of miles. The very small Diego Ramirez Islands lie about 50 km (30 mi) south of Cape Horn.
There is no significant land anywhere around the world at the latitudes of the Drake Passage, which is important to the unimpeded flow of the Antarctic Circumpolar Current which carries a huge volume of water (about 600 times the flow of the Amazon River) through the Passage and around Antarctica.
The passage is known to have been closed until around 41 million years ago[2] according to a chemical study of fishteeth found in oceanicsedimentary rock. Before the passage opened, the Atlantic and Pacific Oceans were separated entirely with Antarctica being much warmer and having no ice cap. The joining of the two great oceans started the Antarctic Circumpolar Current and cooled the continent significantly.