Global climate change
The worldwide climate is changing. The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change. The IPCC postulated in the Fourth Assessment Report. „
Climate Change 2007", the global average temperature increased about 0.76 ° C in the past 100 years.
In the Antarctic the trend of global warming is not so significant than in Arctic. In the Ross Sea the Sea-ice duration has increased, while in the Bellinghausen and Ammundsen Seas it has decreased.
Indeed the West-Antarctic shows dramatic thinning of the ice sheet and deglaciation. The deglaciation not only affects the population of biotic communities it also affected the soil / earth. There are parts of the earth which were covered by ice for hundreds of years that are now exposed.
South Georgia, introduction into local geology
South Georgia belongs to a submerged ridge of mountains that connects the Antarctic continent with the southern tip of South America, called the “Scotia Arc or Ridge”. Unlike most isolated islands South Georgia is not a volcanic island. Most rocks here on the island are sedimental rocks of type sand stone. The oldest rocks belong to the remnants of the ancient supercontinent Gondwana.
Fortuna Bay, introduction into glaciology
The mountains and rocks of South Georgia were shaped by glaciation. The first glaciers formed about 5 million years ago. The five biggest glaciers (Brogger, Neumayer, Nordenskjöld, Esmark and Novosilski) does change very little during the last 130 years. All of them float into the sea. But many glaciers ending on land have receded up to several hundred meters during the last 30 years as it happens to König/Fortuna glacier here in Fortuna Bay. The end morains you see at the coast line were ice-covered in 1956!
Image 1 : View to König glacier from Fortuna Bay
As the island was released of the weight of ice by melting, it lifted up of the sea leaving beaches stranded above the present coast line. A raised former beach, many moraines and glacier outwash forms Fortuna Bay today.
Glacial traces
General glacial traces are moraines and glacial lakes. In addition we can find characteristic “small” traces on the former beach. Here at Fortuna Bay you can find many flat grey stones that contains parallel quartz seams of about 1 mm thickness. See image 2.
Image 2 : Stone with glacial traces
The stone material is slate stone, a quite soft material. The movement of glacier ice removes the softer parts of the stones in a kind of sanding process. The harder quartz seams remain. This gives the stones a characteristic shape, see image 2.
Image 3 : Profile of the stone
Logging Tasks
Find one of these characteristic stones and make a drawing of its profile and add it to your log. Feel free to find a different kind of stone that shows glacial traces, there are many.
Take a photo of the situation of König Glacier and add it to your log. Compare your image with images of the cache gallery. Does the glacier retreat? Write your suggestion to our profile-mail. Feel free to log directly.
Sources :
IPCC, Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007
Robert Burton, South Georgia, The Government of South Georgia and The South Sandwich Islands, ISBN 0-9529008-1-5