The geological structure of Great Britain is complex, resulting as it does from a long and varied geological history spanning more than two billion years. This piece of the Earth's crust has experienced several episodes of mountain building or 'orogenies', each of which has added further complexity to the picture. A wide range of geological structures occur across Britain and include examples at a variety of scales of: * faults * thrust faults * folds * sedimentary basins * grabens and horsts * unconformities