Antarctica (南极洲) is actually a desert. It is the only continent (大陆) on the Earth without any rivers or lakes. Antarctica is covered by ice all year round. The warmest temperature ever recorded there at the South Pole is zero. Explorers (探险家) used to think that a place so cold would have heavy snowfalls. But less than 25.4 cm of snow falls each year. That is equal to less than 1.2 cm of water. Ten times that much moisture (水分) falls in parts of the Sahara Desert (撒哈拉沙漠). The little snow that falls in Antarctica never melts . It continues to pile up deeper and deeper year after year, century after century. When the snow gets to be about 243.8 cm deep, it turn to ice, due to the weight of the snow above it.