Intrusive and extrusive volcanic activity in the UK

Distribution of volcanic activity in the UK
· Apart from hot springs, the UK has no current volcanic activity. However, there is much geological evidence of such activity, which occurred during the mountain-building periods of the Caledonian, Hercynian and Alpine orogenies (mountain-building periods)
· Granites and other examples of intruded rocks occur across the Grampians in Scotland, in Ireland and particularly in southwest of England where the top of an exposed batholith is seen in areas such as Dartmoor and Bodmin Moor. Here, weathering and erosion have combined to give a distinctive landscape of upland plateaux capped by rock outcrops, which are known as tors
· Dykes and sills are also common. The dyke ‘swarms’that radiate across the Isle of Arran in Scotland contain around 500 features in a 20km stretch of coastline. Dykes generally occur as small ridges in the landscape because they are more resistant than the surrounding rocks. The Great Whin Sill runs across large distances in the north of England, forming an upstanding cliff-like feature. Many rivers produce high waterfalls as they plunge over it, for example High Force and Cauldron Snout in the Tees Valley in the Pennines. It is also the defensive base for man-made features such as Hadrian’s Wall and Bamburgh Castle
· Basaltic flows can be seen where the Antrim lava plateaux formed in Northern Ireland. When the lava cooled, vertical cracks in the flow resulted in hexagonal columns. There are exposed to the coast – the Giant’s Causeway. The same volcanic feature can be seen in Fingal’s Cave on the Isle of Staffa in Scotland
· A volcanic plug from a long-extinct volcano (active over 300 million years ago) forms the site of Edinburgh Castle. Stirling Castle is also built on a volcanic plug