The polar landmasses we see today have shifted in relation to the North Pole as well as to each other over time, transported with shifting tectonic plates. Marine sedimentation throughout the years, largely occurring in between the rock shields, has lent itself to the partial submersion of the shields as well as geologic folding, which produced mountains—many of which have eroded over time. Information gathered from the final glaciation occurring 80,, years ago indicates that the Atlantic Arctic islands were coated in ice excepting where nunataks—secluded mountain peaks—poked out of the ice shields.
While northeastern Siberia appeared to have avoided substantial glaciation during this final period, the region had experienced heavy glaciation during earlier periods. The massive ice sheets served to carve unique landforms throughout the Arctic and beyond. Finland the the northern Canadian Shield were left with numerous lakes and lowlands filled with glacial deposits, producing more even terrain interspersed with glaciated ridges such as moraines.
Higher elevations were similarly marked with U-shaped valleys—many of which can be partially seen near the Arctic coasts where they peak out of the water as fjords. However, as the ice sheets melted, the crust regained its original latitude, leaving elevated strandlines coated with the skeletons of marine life, shells and other detritus. The Canadian Arctic boasts of some of the highest strandlines, with some reaching ft, while the coasts of Labrador and Baffin Bay have lower strandlines.
When animal life evolved, the carbon dioxide content of the atmosphere was much higher than now. Some estimates put it at 15—20 times higher.
Hole the Size of Maine Opens in Antarctica Ice
As the oxygen content grew it eventually reached the stratosphere, where it was converted to ozone, providing protection from ultraviolet rays. When this happened, plant life moved from the oceans to the land and then land animals evolved to feed on the plant life. About million years ago Gondwana really began to disintegrate, with India and South America-Africa departing. The links between Australia and Antarctica remained very strong until about 55 million years, when Australia began moving north quickly, allowing Antarctica to become isolated for the first time since animals evolved.
At about 30 million years the Antarctic Circumpolar circulation evolved, the Southern Ocean began to circulate around the southern world, and the modern Antarctic environment evolved.
When Antarctica was a tropical paradise
Until 55 million years ago, the history of life on Antarctica was very similar to that on other southern continents, especially Australia. The fossil record is very similar, with abundant plants and animals, including those that lived on land.
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There are abundant plant fossils in many areas of Antarctica from this period. Perhaps historically, the most significant evidence of earlier vegetation, well preserved in Antarctica, is the leaf form Glossopteris, which was at the heart of the concept of Gondwana — an hypothesis first proposed to explain the widespread distribution of glacial rocks and Glossopteris.
When Robert Falcon Scott and his men were found dead in their tent on the way back from the South Pole, specimens of Glossopteris from the Beardmore Glacier region were found with them.
While they had jettisoned almost everything else on the way back, they recognised the immense scientific importance of Glossopteris and refused to leave the specimens behind. These specimens are some — million years old. There is a major dispute about when Antarctic vegetation died out.
It is clear that a good vegetation cover — containing many elements that still exist in some southern hemisphere cold temperate rainforests such as Tasmania, New Zealand and southern South America — continued in Antarctica until about 35 million years ago. However, there are other tantalising pieces of evidence to suggest it continued until even much more recently.
For example, abundant remains of the southern beech Nothofagus N. The age is contentious but may be as young as 2—3 million years, suggesting that the modern ice sheet-covered environment of Antarctica may be a more recent development than previously thought. The leaves occur abundantly in lake sediments which are in turn under- and over-lain by glacial sediments.
The leaves are very similar but larger than the Tasmanian species Nothofagus gunnii, also known as the Deciduous Beech or Tanglefoot.
Study of the wood suggests that the plant grew as a straggly shrub, similar in growth form to the Arctic willow Salix arctica. Dinosaurs lived in Antarctica and are particularly well known from the northern tip of the Antarctic Peninsula although few have been described formally.
They include ankylosaurs the armoured dinosaurs , mosasaurs and plesiosaurs both marine reptilian groups. Seymour Island, just off the Antarctic Peninsula, is one of the most important fossil sites on earth.
Marine Plain in the Vestfold Hills is another important locality which is yielding a great diversity of fossils from 4. Perhaps the best known are the fossil dolphins and whales. About 5 or 6 species are known but only two dolphins have been studied in detail. The dolphins are new to science and are very different from modern dolphins.
They are quite common and occur as almost complete skeletons as if they died and sank gently into the mud without being disturbed by predators or rough sea conditions. They died in an embayment which was less than 40 metres deep. They consist of two species, one about 4.
Related Geological History of the Polar Oceans: Arctic versus Antarctic
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