Клох Хед: Геология и Маршруты Озерного края

Mountain in the English Lake District, Cumbria, England

Clough Head (/pron//k//l//ʌ//f// //h//ɛ//d/) (meaning: hill top above the ravine) is a fell, or hill, in the English Lake District. It marks the northern end of the main ridge of the Helvellyn range and is often walked as part of the ridge walk. The fell stands south of the village of Threlkeld and the A66 road, and it forms the steep eastern side of the tranquil valley of St John's in the Vale. On its western side the fell displays a dark mass of rocky crags and a deep set rocky ravine. On the other side it has smooth grassy slopes. Beneath the north face is the steep valley or clough from which Clough Head gets its name. Also beneath the steep northern face lies the lower hill of Threlkeld Knotts, a granite hill which has been much quarried round its margin. A number of different types of rock are found on and around Clough Head, which were formed in very different circumstances. These include deep sea sedimentation, effusive volcanic lava flows, explosive volcanism, an intrusion of granite, mineralisation and finally glacial sculpting. To understand the geology of Clough Head is to understand much of the geology of the Lake District. An old route known as the Old Coach Road passes beneath Clough Head. Most of the fell is Open Access land, which walkers can enter from either end of the Old Coach Road, or from a lane south of the village of Threlkeld. Four main routes lead to the summit.

Threlkeld Knotts (meaning: the knobbly hill above Threlkeld) is a lower, rounded hill, nestling against and overshadowed by the steep northern face of Clough Head. Its curving summit ridge contains three small tops, Remains of enclosure walls may still be seen, about north of the Old Coach Road. as it crosses from Wanthwaite (/pron//'//w//ɒ//n//.//θ//ɛ//t/ Near the summit of the road is Hause Well, a spring issuing from a crevice in the rock. Sandbed Gill was the first new route in the Lake District to be pioneered by the brothers George and Ashley Abraham in 1890. Although George was only 18 at the time, and Ashley 14, they had already gained true rock climbing skills elsewhere in the Lakes. Walkers should leave the gill well alone.

The summit is marked by an Ordnance Survey triangulation column and a wind shelter. It provides a good view of Blencathra to the north, and a wide, all round view, broken only by Great Dodd, with glimpses of both the Solway Firth to the north and Morecambe Bay to the south. Mudstones, siltstones and sandstones which had been deposited in deep water on the northern margin of an ancient continent (Avalonia) in the early Ordovician Period were chaotically disrupted by a huge undersea avalanche to form an olistostrome deposit in which blocks of rock are now embedded in a matrix of mudstone, and intensely deformed by minor folds, slumps and shears. This event can be dated to about 460 million years ago. The deep sea deposits of the Skiddaw Group were raised above sea level by the subduction of ocean crust from the north beneath the continent to the south. This uplift was followed by a brief (about 5 million years) period of intense volcanic activity, up to about 450 million years ago. In the area to the north of Sticks Pass the Birker Fell andesites are overlain by the Lincomb Tarns Tuff Formation. This formation is one of the most widespread of the volcanic rocks of the Lake District; it seems that the whole district was buried beneath at least 150 m of densely welded ignimbrite, a rock formed from a pyroclastic flow of very hot gas and rock. This formation must represent a series of eruptions of truly exceptional magnitude, accompanying the formation of a volcanic caldera probably in the area around what is now Helvellyn. The quarry closed in the 1980s and now houses the Threlkeld Quarry and Mining Museum. Mineral veins have been formed in many Lake District rocks by hydrothermal circulation of groundwater though geological faults and are often associated with the granite batholith. The lower promontory of Threlkeld Knotts north of Clough Head is scarred and flanked by 'rock slope failure' fractures and landslips, and views from the A66 and Blencathra could suggest that the whole mass of the Knotts has descended from the concavity in the north face, which is not a true glacial cirque (Lakeland combe), but this remains debatable. Rock slope failure also patterns White Pike with antiscarps (uphill facing scarplets), which could formerly have extended across the Clough Head cavity.

Clough Head was called Threlkeld Fell in Thomas West's 1778 guide book. Its present name, Clough Head, was first recorded by the Ordnance Survey in 1867. Clough is a dialect word from the Old English clōh, a ravine. This appears to be a reference to a steep valley just below Red Screes, and which contains a sheepfold called Clough Fold. White Pike is "the pale summit," recorded since 1774, probably named from its pale coloured rock, and perhaps in contrast to the reddish colour of Red Screes beneath the main summit. Fisher's Wife's Rake is "Mrs Fisher's Path." Rake is a dialect word of unknown origin which refers to a narrow path on a hill. Mark Richards claims that the name comes from the Fisher family of Rake How across the valley. He says the husband cut peat on the col above and his wife hauled it down by sled, but he gives no indication of the source of this information.