Even though nothing is seen on the surface and silence is part of the icy landscape, there's a whole variety of life waiting to be discovered beneath this white desert. Antarctica, the great white continent, is located some 620 miles (1,000 km) south of Ushuaia. Covering almost 5,405,000 square miles (14,000,000 sq km), its surface consists of a gigantic layer of ice which is up to 13,000 feet thick (4,000 m) extending over a continental mass of about 3,500,000 square miles (9,000,000 sq km). Covering a surface of 5,446,989 square miles (14,107,637 sq km), Antarctica is the fourth largest continent, after Asia, America and Africa. It's the highest one on Earth, with an average altitude of 6,560 feet (2,000 m) above sea level. About 80% of the planet's fresh water is in this continent, which is also the source of the greatest ecological variety. Animals only dwell by the sea, where whales, seals and penguins, among other species, live most of their lives. Among mammals, you'll find blue whales, Southern right whales, orcas and sea elephants. Among the different types of birds, you'll find penguins, albatrosses, petrels and scubas, among others. The weather is severe and is characterized by temperatures which descend to -40 ºF (-40 ºC), though, in the summer and with good weather, the average temperature in the Antarctic peninsula varies at 19 ºF (-7 ºC). During that part of the year, the continental mass reaches up to 5,405,000 square miles (14,000,000 sq km). During the winter, the surrounding sea freezes, and sea ice forms, then the surface goes up to 11,583,000 square miles (30,000,000 sq km). This happens every year, which is the reason why Antarctica is known as the "Pulsing Continent". Tourism in Antarctica consists of cruises which leave Ushuaia between November and March and, according to their itineraries, last between a week and two months. Tourists get to know the white continent, one of the areas on the planet that's been explored the least. Petrel, Esperanza and Jubany scientific bases are included in the itineraries because they are very relevant in terms of fauna and landscapes. Cape Horn, Shetland Islands, Malvinas (Falkland) Islands and the northern extreme of the Antarctic peninsula are the most frequently visited places. Nowadays, thanks to the Antarctic Treaty, countries such as Argentina, Australia, Chile, France, the United Kingdom, New Zealand, Norway, Belgium, Japan, the former Union of South Africa, the former USSR and the United States are able to carry out scientific and technical research on Antarctic ground.