Prehistory of Antarctica
Like all other continents, Antarctica has at its core an ancient shield. The rocks of the East Antarctica shield are as old as 4 billion years, which means that they are amongst the oldest known rocks on Earth. Geologists are now studying this shield to help them gain insight into the early geological processes of the Earth’s history.
In many ways, the evolution of Antarctica appears to be similar to that of Australia. The fossil record of the two continents is similar, and Antarctica has yielded dinosaurs, amphibians and even marsupials from ages when the continents were joined.
The position of the continents shifts constantly and the geography of today's world is vastly different from what it was even a hundred million years ago. Twenty million years before the dinosaurs became extinct, Australia, Antarctica and South America were part of the same land mass called Gondwana. In those days Antarctica was not covered in ice, even though it was at the South Pole. Animals passed freely from South America through Antarctica to Australia, and the plant species of Gondwana were also closely related to each other.
Eighty five million years ago Australia began to separate from Antarctica. The separation started slowly at first at a rate of only a few millimetres a year. This then accelerated to the present rate of 7 cm a year. Australia completely separated from Antarctica about 30 million years ago.
Scientists in Antarctica have discovered fossilised spores and pollen of sundews, Nothofagus (which includes the Tasmanian myrtle N. cunninghamii and the Tasmanian deciduous beech N. gunnii ). The Tasmanian tree fern and creeping pine, are derived from forms which once inhabited Australia and Antarctica. Scientists were recently excited by a fossil discovery of twigs, roots, leaves and pollen in Antarctica, of a form which is virtually indistinguishable from Nothofagus gunnii , the Tasmanian deciduous beech. These fossils may be ‘only’ 3 million years old. This implies that Antarctica was not entirely covered by ice at that time. Previous to this find, scientists had thought that Antarctica cooled and became ice bound after Australia and South America separated 30 million years ago, allowing the Circumpolar Current to develop. Scientists are still debating the age and significance of this fossil discovery.
Antarctica without its ice
People who consider Antarctica to be a small continent will be surprised to discover that it is larger than Europe and nearly twice the size of Australia. The Antarctic continent, excluding its ice shelves, covers over 13 million square kilometres compared with 7.7 million km² for Australia, or 10.5 million km² for Europe. The map below gives some idea of relative size.
Ninety-nine percent of Antarctica has a permanent blanket of snow and ice. Only about one percent of the continent's rock base is visible where it pokes through the ice sheet in the form of coastal outcrops, mountain ranges or ‘nunataks’ which are isolated peaks.
The Transantarctic Mountains divide the continent into two contrasting parts, the East and West. The Transantarctic Mountains constitute one of the world’s longest and most impressive mountain chains. They extend from the north western corner of the Ross Sea to the south western corner of the Weddell Sea. West Antarctica, which includes the Antarctic Peninsula, is smaller and has a complex geological history. West Antarctica consists of four land units each with a different history. There has been major volcanic activity here in recent geological times and there are still a few active volcanic centres. Deep waters exist between land units and the West Antarctic ice sheet, which can be considered to a be floating ice mass, held in place by land peaks. West Antarctica includes the Vinson Massif, which has the highest peak in Antarctica at 5140 metres.
Most of East Antarctica is still not well known by geologists but it does include the Transantarctic Mountains. These commonly exceed 4000 metres elevation. The shield is very depressed in the centre, where it carries the bulk of the Antarctic ice sheet. Large areas lie deeper than 1000 metres below sea level.
There are deposits of minerals such as coal and iron ore, but there are vast economic and technical difficulties associated with the recovery of mineral deposits. The Antarctic ice cover is, on average, 2.5 km thick and this means that very little of the land is accessible for exploration, so work would have to take place under the ice sheet. The difficult Antarctic conditions, even when the technology works well elsewhere make exploitation unlikely. Once minerals are mined, Antarctica is a long way from world markets, and material would have to be transported over the treacherous Southern Ocean. Cheaper sources exist elsewhere in the world, and these will be exploited before Antarctic sources.
So far, the economics of extracting resources from the harsh Antarctic environment have prevented any commercial operations, but Antarctica's climate may not protect its minerals indefinitely. What can prevent such exploitation is a strong, well-supported international agreement. Nations of the Antarctic Treaty System agreed in 1991 to put a halt to the exploitation of minerals when they signed a comprehensive Protocol on Environmental Protection (the Madrid Protocol), which banned mining in Antarctica indefinitely. This important agreement came into force in January 1998.
- Wendy Rockliffe, Patrick Quilty, Australian Antarctic Division