Door 18: Borrowdale Volcanics & Crinkle Crags
Jamie Farquharson sent us this image of the Borrowdale Volcanics for the 2015 Earth Science Week photography competition, based on our 100 Great Geosites.
Borrowdale is a valley in the English Lake District in the Borough of Allerdale in Cumbria. The valley lends its name to the Borrowdale Volcanic Group, which make up most of the mountains at the head of Borrowdale including Scafell Pike.
The Crinkle Crags are a classic and complex area of volcanic geology, dating from the late Ordovician. The Borrowdale volcanic group are a series of andesitic lavas and pyroclastic rocks, erupted from an arc of volcanoes that had developed above an active subduction zone – in this case, along the southern margin of the Iapetus ocean.
The complexities of the volcanic geology of arc volcanoes – which show rapid variations in lithofacies and depositional environments, and post-depositional modification ranging from redeposition to caldera-formation – means that much of the detail of the eruptive history has only been worked out within the past couple of decades.