Antarctica does not have a town, a tree, or even a blade of grass on the entire continent. That does not mean that Antarctica is not vital to life on earth. Seventy percent of the world's fresh water is frozen atop the continent. These icecaps reflect warmth from the Sun back into the atmosphere, preventing planet Earth from overheating. Huge icebergs break away from the stationary ice and flow north to mix with warm water from the equator, producing currents, clouds, and complex weather patterns. Creatures as small as microscopic phytoplankton and as large as whales live on and around the continent, including more than 40 species of birds. Thus, the continent provides habitats for vital links in the world's food chain.
Geologists believe that, millions of years ago, Antarctica was part of a larger continent called Gondwanaland, based on findings of similar fossils, rocks, and other geological features on all of the other southern continents. About 200 million years ago, Gondwanaland broke apart into the separate continents of Antarctica, Africa, Australia, South America, and India (which later collided with Asia to merge with that continent). Antarctica and these other continents drifted away from each other as a result of shifting of the plates of the earth's crust, a process called continental drift that continues today. The continent is currently centered roughly on the geographic South Pole, the point where all south latitudinal lines meet. It is the most isolated continent on earth, 600 mi (1,000 km) from the southernmost tip of South America and more than 1,550 mi (2,494 km) away from Australia.
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