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The Falkland Islands are located in the South Atlantic Ocean between 51°S and 53°S on a projection of the Patagonian Shelf, part of the South American continental shelf. In ancient geological time this shelf was part of Gondwana, and around 400 million years ago split from what is now Africa and drifted westwards from it. Today the islands are subjected to the Roaring Forties, winds that shape both their geography and climate. The Falklands comprise two main islands, West Falkland and East Falkland, and about 776 small islands. ==Geology== (詳細はgeological history of the Falkland Islands began during the Precambrian era more than 1000 million years ago, when Proterozoic granites and gneisses were laid down in Gondwana. These rocks became part of the Cape Meredith/ formation and outcrop at the Cape.〔(BGS paper )〕 During the Siluro-Devonian era, these rocks were overlain with quartzose and subarkosic sandstones with some siltstone and mudstone, rocks that are particularly erosion- and weather-resistant, giving these parts of the islands a rugged landscape and coastline.〔 Tectonic forces continued to form the region: a mountain chain formed, part of which now creates Wickham Heights on East Falkland Island and extends westwards through West Falkland into the Jason Islands. A basin developed and was filled with land-based, or terrigenous, sediments. These layers of sand and mud filled the basin as it sank and as they hardened they produced the rocks of the sedimentary Lafonia Group of the Falklands. These rocks are similar to those in southern Africa's Karoo basin. About 290 million years ago, in the Carboniferous period, an ice age engulfed the area as glaciers advanced from the polar region eroding and transporting rocks. These rocks were deposited as extensive moraines and glacial till, or they sank in the sea while the glacier floated in a layer of ice. When the glacial sediments were turned into stone they formed the rocks that now make up the Fitzroy Tillite Formation in the Falklands. Identical rocks are found in southern Africa.〔 During the break-up of Gondwana and the formation of the Atlantic Ocean some 200 million years ago, minor crustal fragments that were to become the Falkland Islands detached themselves from the nascent African continent and drifted westwards, dividing and rotating as they did so before settling on the Patagonian Shelf.〔(State of the Environment Report 2008 )〕 Most of the layers of West Falkland and its surrounding islands are slightly inclined from the horizontal. This inclination shows different types of rocks in different places. The quartzites of Port Stephens and Stanley are more resistant than the arenaceous sediments of the formation at Fox Bay. The Hornby Mountains, near Falkland Sound have experienced tectonic forces of uplift and folding which has inclined the quartzite beds of Stanley to the vertical. Rocks from more recent geological periods such as the Jurassic, Cretaceous, and Tertiary periods usually contain lime-rich rocks. The absence of such rocks has led to an acidic substrate which manifests itself in the nature of the soil.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Geography of the Falkland Islands」の詳細全文を読む スポンサード リンク
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