Answer:
15 million years
Step-by-step explanation:
Antarctica is the continent that is spread around the South Pole, known for being covered with ice, and being the coldest place on the planet. The glaciation of the continent started around 34 million years, started to speed up since 23 million years ago, and became dominant on this continent only around 15 million years ago. Antarctica has not always been covered in ice, and in fact, through the majority of its geologic history Antarctica has been covered with dense forests. This was possible because the continent was much further north, relatively close to the Equator, thus its climate was tropical, subtropical, and temperate. That all started to change as first Pangaea, and then Gondwanaland broke apart, and Antarctica was the piece that was moving toward the South Pole. As Africa, India, Australia, and at last South America drifted apart from Antarctica, the continent was left surrounded by ocean waters where very cold ocean currents occurred because of the continental drift. On top of it the continent got into a place where the sunlight is very weak, thus gradually it started to freeze and had become almost entirely glaciated.