Summits Lakeland

OUR PLANET OUR PLANET LAKELAND THE MARKS SUMMITS OF A GLACIER PHOTO Glacially scoured scenery on ridge between Grey Knotts and Brandreth. The mountain scenery Many hillwalkers and mountaineers are familiar The glacial scenery is a product of all these aries between the different lava flows, as well as the ridge east of Blea Rigg. However, if you PHOTO LEFT Solidi!ed lava "ows visible of Britain was carved with key features of glacial erosion such as deep phases occurring repeatedly and affecting the as the natural weaknesses within each lava flow, do have a copy of the BGS geology map, close across the ridge on High Rigg. out by glaciation in the U-shaped valleys, corries and the sharp arêtes that whole area, including the summits and high ridges. to create the hummocky landscape. Seen from the attention to what it reveals about the change from PHOTO RIGHT Peri glacial boulder!eld on often separate adjacent corries (and which provide Glacial ‘scouring’ by ice sheets and large glaciers summit of Great Rigg it is possible to discern the one rock formation to another as you trek along the summit plateau of Scafell Pike. not very distant past. some of the best scrambles in the Lakeland fells, are responsible for a typical Lakeland landscape pattern of lava flows running across the ridgeline. the ridge can help explain some of the larger Paul Gannon looks such as Striding Edge and Sharp Edge). of bumpy summit plateaus and blunt ridges. This Similar landscapes can be found throughout the features and height changes. at how the ice le" The products of glacial deposition are also type of landscape is characterised by hummocky great belt of major lava flows that runs across much But why are such landscapes limited in extent its mark on the familiar features of the Lakeland landscape, higher areas separated by tarns and boggy lower of central Lakeland as well as further southwest. to certain areas? especially moraines and drumlins. Moraines areas. Such glacial scouring produces some The long, wide ridgeline that runs eastwards from The answer lies in the fact that ice sheets and summits and ridges sometimes occur in enchanting clusters, such as spectacular scenery where the tarns are perched Pavey Ark and Stickle Tarn towards Chapel Stile very large glaciers do not erode all areas over of the Lake District. Langdale Combe at the head of Great Langdale. high up on a ridge. and Grasmere, is another potentially demanding which they pass equally. Lakeland has many However, there are many other aspects of glacial This type of landscape is found scattered all location for navigators. The geology of the ridge summit areas of smooth ground, such as the WORDS AND PHOTOS BY PAUL GANNON shaping of the mountains which are less familiar, over Lakeland, with spectacular examples between is complex, being formed from a mix of a variety summit areas and western flanks of both the despite having widespread influence on the Blea Rigg and Ambleside on the northern side of of pyroclastic rocks with some limited lava flows. Helvellyn and High Street ridges. The cutting scenery throughout the Lake District and other Great Langdale and Lingmoor Fell on its southern Pyroclastic rocks are formed by explosive or power of ice is concentrated into some areas and mountain areas. side. High Rigg is another classic example, as are fragmental volcanoes. The molten magma erupts glides with little effect across other areas. Ice has shaped not just the deep Rosthwaite Fell and Great Crag. Such areas are as small, medium or large lumps, rather than as identified on OS and Harvey maps by intricate a molten lava flow. The observant fell walker will also note that valleys, corries and crags, but also the patterns of tiny ring contours. The central Lakeland fells including High Street, some summits are awash with boulders strewn higher ground and the summits. These areas can be quite demanding navigation- Hellvellyn, the Langdale Pikes, Bowfell, Scafell ally, especially in poor visibility. When walking Pike and Great Gable, are made up from extensive across their upper reaches, such as is the case The Ice Age started about 2.5 million years ago through these knobbly landscapes, the hummocky areas of pyroclastic rocks ejected in a great number with Scafell Pike and Bowfell. and ended about 11,000 years ago though it was higher areas and the dips seem relentlessly random. of violent explosive eruptions, mixed with limited not a continuous run of cold conditions. There It takes very close attention to the map and the areas of lava flows. were several colder periods interrupted by warmer deployment of the full range of micro-navigation If you look at the British Geological Survey map These boulder fields are the product of what ‘interglacial’ phases (indeed, we are probably in an techniques to say with confidence where you are for this area it looks for all the world as if someone are known as ‘periglacial’ conditions. This involves interglacial phase at the moment). There is direct on the map. However sometimes, when seen from has smashed some pieces of coloured glass and repeated freezing and thawing of water that evidence of at least three intensely cold periods a higher point, a pattern becomes clear. thrown them on the ground, creating a manic enters those natural weaknesses such as joints affecting the Lake District, but there may well The pattern and the landscape is the result of pattern of colours, each representing a different (cracks where there has been no movement), have been more such phases. glacial scouring exploiting more or less regular set of volcanic rocks. The plentiful boundaries faults (cracks where movement has taken place) At the coldest point an ice sheet covered nearly structural weaknesses in the bedrock where the between these different rock ‘formations’ are a and rock boundaries. This can happened in fairly the whole of Lakeland, possibly 1km or more thick, plucking can exert most damage. prime source of weakness where the ice can carve cold conditions before and after a cold phase or it covering all, or all but a few, of the fells. During In the case of High Rigg the main factor behind its escape route. The rocks within each formation can affect any summits sticking out above the ice less cold times, big valley glaciers carved out the the pattern of hummocky land is the fact that the also vary and provide more weaknesses. Also, during a cold phase. major valleys and the higher summits would have rocks are nearly all solidified lava flows (erupted slight contraction of the erupted material as it Ice hasn’t just carved out the corries and stuck out above the ice, with the passing glaciers around 450 million years ago). One flow was laid cooled caused minute cracks in the rocks called the lake-filled deep valleys that give Lakeland Paul Gannon is the author of leaving evidence as ‘trimlines’ scored into such fells on top of another and the process repeated time ‘joints’ which, when exposed at the surface again its name. It has also played a significant role Rock Trails Scottish Highlands as Great Gable. And, at marginally higher temper- and again. The whole lot was then tilted upwards give the ice a way of cracking the rocks open. in shaping the summits. Hummocky high and leads geology workshops atures, only small glaciers existed, occupying the in mountain building to its present angle. In much Unfortunately, unlike High Rigg, there is no ground, smoothed summit plateaux and tedious for mountaineers. high corries, such as Red Tarn under Helvellyn. more recent times the ice has exploited the bound- obvious pattern discernible on a landscape such bouderfields are also ice-made features. ] www.landscape-walks.co.uk 30 » THE PROFESSIONAL MOUNTAINEER WINTER 2015 WINTER 2015 THE PROFESSIONAL MOUNTAINEER » 31.

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