Geology
The geological history of the Falkland Islands began during the pre-Cambrian 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. During the Siluro-Devonianera, 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 mountainous 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. 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 the 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.
Read more about this topic: Geography Of The Falkland Islands