Where to see the Whin Sill You can see dramatic exposures of the Whin Sill at several places in The North Pennines AONB is Britain ’s first UNESCO European northern England. Visit Upper Teesdale in the North Pennines to see Geopark and is a founding member of the UNESCO Global it at the waterfalls of High Force, Low Force and Cauldron Snout, Geoparks Network. Geoparks are places where outstanding and at the crags of Holwick Scars, Falcon Clints and Cronkley Scar. geology is being used to support sustainable development . The To find out more, please contact: Holwick Scars L North Pennines AONB Partnership Weardale Business Centre L The Old Co-op Building Falcon Clints Whin Sill 1 Martin Street Stanhope, Co. Durham DL13 2UY +44 (0)1388 528801 [email protected] www.northpennines.org.uk www.europeangeoparks.org Front cover: High Force, Upper Teesdale Above right: Low Force, Upper Teesdale Unless otherwise credited, all photographs © NPAP/Elizabeth Pickett L We can provide a summary of the On the North Pennine escarpment , near Dufton, the Whin Sill forms a spectacular ring of cliffs towering over the deep valley of information contained in this High Cup Gill . publication in large print, different formats and other languages on request. Please call 01388 528801 for details. This leaflet was produced as part of the Rockworks project – an initiative of the: Rockworks is supported by: In Weardale you can see the Little Whin Sill in the Rookhope Burn and in the disused quarry at Greenfoot, near Stanhope. This publication is printed on Greencoat Plus Velvet paper: 80% recycled post consumer, FSC certification; NAPM recycled certification; 10%TCF virgin fibre; 10% ECF fibre. In the Northumberland Coast AONB the Whin Sill forms the After you have finished with this leaflet please give it to someone else to read, or recycle it. Farne Islands and some dramatic stretches of coastline. In the Northumberland National Park the Whin Sill is a formidable natural rampart for Hadrian’s Wall. K The North Pennines AONB Partnership holds a Gold GTBS Award 6 / 8 0 for its corporate office and tourism activities. / 0 1 The Whin Sill is one of the most famous and dramatic natural Working the whinstone features of the North Pennines – and its origins are just as spectacular . There is a long history of whinstone quarrying in the North Its formidable cliffs and rocky crags tell a story of molten rock, Pennines, and the industry continues today at Force Garth Quarry in Upper Teesdale, where the Whin Sill is worked for roadstone . minerals, quarrymen and worldwide fame! Middleton Quarry L Molten rock in the early 20th About 295 million years ago, molten rock, or magma , at over century. The stone 1000°C , rose up from deep within the Earth. The magma spread Sandstone Shale blocks piled in the out between the layers of limestone, sandstone and shale which Limestone foreground are lie beneath much of the North Pennines. It cooled and solidified whinstone ‘setts’ underground to form a huge sheet of rock up to 90 m thick – for paving. the Whin Sill. This is made of a hard dark rock called dolerite or, Reproduction rights kindly given as it is known locally, whinstone . Dolerite is a type of igneous by the Photographic Archive, k Beamish Museum Ltd. c rock – one which is formed when molten rock solidifies . After o Whin Sill r P n millions of years of erosion the Whin Sill is now exposed at the A P e N t / t l surface in several places . t e o L k c i P How the Whin Sill formed M h t e b a z i l L Crystal kaleidoscope E © The now disused Look closely at a piece of freshly broken dolerite and you’ll Greenfoot Quarry, see that it is a mass of small crystals. The dark crystals are Cracks and columns near Stanhope in the mineral pyroxene and the white flecks are feldspar. Weardale, produced These minerals crystallised out of the magma as it cooled. The Whin Sill probably took crushed rock from When cut into very thin slices, only about 0.03 mm thick, around 50 years to cool from the Little Whin Sill, a and viewed under a polarising microscope, the Whin Sill molten rock to solid dolerite. thinner sheet of has jewel-like colours and intricate crystal shapes. During the final stages of cooling it contracted, producing vertical dolerite which lies A microscopic view of the Whin Sill, cracks along which the rock above the main viewed under polarised light. breaks into rough columns. You Whin Sill . can see these cracks and columns Actual size in Whin Sill cliffs and quarry faces. L Dolerite is rarely used as a L Columns in the Whin building stone as it is very Pyroxene Sill at High Cup Gill hard and difficult to work. However, in places like Cooked rocks Holwick in Upper Teesdale, which are close When the Whin Sill was molten it to outcrops of the Whin had a huge effect on the surrounding Sill, a few buildings are rocks. In Upper Teesdale, a limestone made of dolerite. layer was baked and altered to a white, crumbly, crystalline marble, What’s in a name ? Iron oxide known as ‘Sugar Limestone’. This unusual rock supports the unique The Whin Sill took its name from terms used by northern ‘Teesdale Assemblage’ of arctic- quarrymen – ‘whin’ was a hard dark rock and a ‘sill’ was alpine plants, including the beautiful any flat-lying layer of rock. When 19th century geologists spring gentian. worked out how the Whin Sill formed, the word ‘sill’ was adopted for all similar bodies of igneous rock worldwide. Feldspar Sugar Limestone near The Whin Sill is therefore famous for being the original sill L Cow Green Reservoir of geological science! Reproduced with permission of the British Geological Survey © NERC. All rights reserved..