Antarctica

I

Introduction

Antarctica, fifth-largest of the Earth's seven continents, located almost entirely south of latitude 66°33' south (the Antarctic Circle), and surrounding the South Pole. It is mostly circular in shape with a long arm—the Antarctic Peninsula—reaching out towards South America, and with two large indentations, the Ross and Weddell seas and their ice shelves. Its total area is about 14.2 million sq km (5.5 million sq mi) in summer. During the winter Antarctica doubles in size because of the large amount of sea ice that forms at its periphery. The true boundary of Antarctica is not the coastline of the continent itself but the Antarctic Convergence, which is a sharply defined zone in the southern extremities of the Atlantic, Indian, and Pacific oceans between about latitude 48° south and latitude 60° south. At this point, the colder waters flowing north from Antarctica mix with warmer waters moving south. The Antarctic Convergence marks a definite physical difference in the oceans. For these reasons, the water surrounding the Antarctic continent is considered an ocean in itself, often known as the Antarctic, or Southern Ocean.

Antarctica has no native population. Its residents are scientific and support staffs who usually stay no more than a year at a time. The first person born in Antarctica was Emilio Palma, the son of the commander of Argentina's Esperanza Base, on January 7, 1978.

Antarctica is more than 95 per cent ice covered and contains about 90 per cent of the world's fresh water. Because of its thick ice cover, it is the highest of all continents, with an average elevation of about 2,300 m (7,500 ft). The highest point on the continent is Vinson Massif (4,897 m/16,066 ft); the lowest point appears to be the Bentley Subglacial Trench (2,499 m/8,200 ft below sea level) in West Antarctica. This trench is covered with more than 3,000 m (9,840 ft) of ice and snow. Lower points may exist under the ice, but they have not yet been discovered.

Seven nations had announced territorial claims to parts of Antarctica, but since the Antarctic Treaty of 1959, enforced in 1961, these claims have been held aside in the interests of international cooperation in scientific research. (The claims had been made by Argentina, Australia, Chile, France, Great Britain, New Zealand, and Norway.)

II

The Natural Environment

Antarctica exists today in an ice age. Future economic development of the ice-covered land mass is highly unlikely. Resource exploitation on the continental shelf is possible, but certainly not for many years to come. Marine life in the waters surrounding Antarctica is currently being developed economically. This marine life includes whales and a tiny, shrimp-like animal called krill.

A

Geological History

Antarctica was a central part of the former supercontinent Gondwanaland (see also Plate Tectonics). As Gondwanaland broke apart during the late Mesozoic and early Cenozoic eras (some 100 million years ago) to form the continents of the southern hemisphere, Antarctica drifted from the Tropical Zone to its present polar position. In 1999 a large collection of important fossils was uncovered on the Antarctic Peninsula and several nearby islands. The fossils included the vertebrae, teeth, jaws, and partial skeletons of mosasaurs and plesiosaurs. Both were types of large, ocean-dwelling reptiles that lived during the late Cretaceous Period, which ended with their extinction—along with that of the dinosaurs—about 65 million years ago. The discoveries provided further evidence that Antarctica was a subtropical region millions of years ago, when the continents were much closer than they are today and had connecting marine corridors. The mosasaurs and plesiosaurs were thought to have arrived in Antarctica about 75 million years ago.

B

Physiographic Regions

Antarctica consists of two main geological areas. The larger of these, East Antarctica, is located mostly in the eastern hemisphere. It is probably a Precambrian shield, over 570 million years old, covered by thousands of metres of ice. West Antarctica, lying mostly within the western hemisphere, appears to be a continuation of the Andes of South America; glaciologists and geologists speculate that West Antarctica would become an island archipelago if the ice cover were removed.

The two areas of Antarctica are separated by the Transantarctic Mountains, an uplift zone of mountains that extends across the entire continent, although portions are buried under the ice cover. Within these mountains are found many coal deposits and fossil remains related to the earlier tropical climate of Antarctica.

In East Antarctica the geologically stable Precambrian shield is generally covered by sedimentary or igneous deposits. The geological structure of West Antarctica is less well known, but at least two active volcanoes are found in the area, the higher of which is Mount Erebus (3,794 m/12,448 ft). Antarctic soils are classified as dry polar desert soils, and their occurrence is limited to the several deglaciated (ice-free) valleys or oases and to parts of the northern Antarctic Peninsula.