The Pennine Way. Paddy Dillon
Чтение книги онлайн.
Читать онлайн книгу The Pennine Way - Paddy Dillon страница 7
Название: The Pennine Way
Автор: Paddy Dillon
Издательство: Ingram
Жанр: Книги о Путешествиях
isbn: 9781783624768
isbn:
The underlying geology of the Pennines shapes the scenery along the Pennine Way. The Dark Peak and the South Pennines, whose foundations are sandstones and shales, with gritstone ‘edges’, give rise to acid clay soils, which encourages the formation of thick blanket bog. This bog has been growing for the past 7000 years, but in many places it is decaying, so that the moorlands are riven by peat channels, or ‘groughs’, with high banks of peat between them, known as ‘hags’. Given that the blanket bogs absorb considerable amounts of carbon dioxide, their rapid decay gives cause for concern and efforts are being made to stabilise the remaining bogs and reverse the trend.
Where limestone dominates, particularly in the Yorkshire Dales but also in parts of the North Pennines, the landscape often looks fresh and green, covered in short, dense, sheep-grazed turf, with bright cliffs and outcrops, or ‘scars’, of limestone poking through. Limestone country is fascinating, mostly because of the way the rock dissolves slowly over the aeons, giving rise to a distinctive landscape known as ‘karst’ topography. Limestone doesn’t just wear down like other rocks but dissolves inside itself, becoming riddled with caves and passages. When these are close to the surface, they may collapse, forming ‘shake holes’.
In the North Pennines, the existence of the igneous Whin Sill, sandwiched between older beds of rock, forms some of the most striking landscapes in the North Pennines and Northumberland. The mighty Teesdale waterfalls, the striking High Cup and the rugged crest bearing Hadrian’s Wall are all formed by the Whin Sill, which also outcrops along the Northumberland coast.
Technically, and geologically, the Pennines end just south of Hadrian’s Wall, so the continuation northwards through Northumberland results in another shift in the scenery. While Carboniferous rocks lie underfoot at first, by the time the high Cheviot Hills are reached, the bedrock is either lava or granite. The central granite mass of The Cheviot stands broad-shouldered, with all the other Cheviot Hills huddled around it. The poor acid soil supports thick blanket bog. Many walkers, seeing the Cheviot Hills after spending so long in the Pennines, are surprised at how hilly they are, but this is short-lived, as the Pennine Way ends suddenly with a descent into rolling, pastoral countryside.
The Helm Wind
Most walkers on the Pennine Way hear about the ‘Helm Wind’ but few understand what it is. The Helm Wind is the only wind in Britain with a name. It only blows from one direction and it gives rise to a peculiar set of conditions. Other winds blow from all points of the compass, but the Helm is very strictly defined, restricted to the East Fellside flank of the North Pennines, and according to local lore, no matter how much it rages, it cannot cross the Eden.
The Helm Wind blows down the steep western slopes of the North Pennines
First, there needs to be a northeasterly wind, with a minimum speed of 25kph (15mph), which the Beaufort Scale calls a ‘moderate breeze’. This isn’t the prevailing wind direction and it tends to occur chiefly in the winter and spring. Track the air mass from the North Sea, across low-lying country, as far as the Tyne Gap. The air gets pushed over Hexhamshire Common, crossing moorlands at around 300m (1000ft). It next crosses moorlands at around 600m (2000ft) and then Cross Fell and its neighbours are reached at almost 900m (3000ft). There are no low-lying gaps through the North Pennines, so there is nowhere for the air mass to go but over the top.
As the air is pushed up from sea level, it cools considerably. Any moisture it picked up from the sea condenses to form clouds, and these are most noticeable as they build up above the East Fellside. This feature is known as the ‘Helm Cap’. If there is little moisture present it is white, while a greater moisture content makes it much darker, resulting in rainfall. Bear in mind at this point that the air mass is not only cooler, but as a result it is also denser than the air mass sitting in the Vale of Eden.
After crossing the highest parts of the North Pennines, the northeasterly wind is cold, dense, and suddenly runs out of high ground. The air literally ‘falls’ down the East Fellside slope, and if it could be seen, it would probably look like a tidal wave. This, and only this, is the Helm Wind. The greater the northeasterly wind speed, the greater the force with which it plummets down the East Fellside, and if it is particularly strong, wet and cold, it is capable of great damage. Very few habitations have ever been built on this slope, and the villages below were generally built with their backs to the East Fellside, and most of them originally lacked doors and windows on their windward sides.
The air mass now does some peculiar things, having dropped, cold and dense, to hit a relatively warm air mass sitting in the Vale of Eden. A ‘wave’ of air literally rises up and curls back on itself. As warm and cold air mix, there is another phase of condensation inside an aerial vortex, resulting in the formation of a thin, twisting band of cloud that seems to hover mid-air, no matter how hard the wind blows at ground level. This cloud is called the ‘Helm Bar’ and is conclusive proof that the Helm Wind is ‘on’, as the locals say.
Local folk say that no matter how hard the Helm Wind blows, it can never cross the Eden. All the wind’s energy is expended in aerial acrobatics on the East Fellside, where it can roar and rumble, while the Vale of Eden experiences only gentle surface winds. Northeasterly winds are uncommon and short-lived, so after only a few days the system breaks down and the usual blustery southwesterly winds are restored. In the meantime, don’t refer to any old wind as the Helm Wind until all its characteristics have been noted, including the northeast wind, the Helm Cap and the Helm Bar.
Wildlife
Swaledale sheep are common throughout the Yorkshire Dales
Pennine pastures offer good grazing for sheep and cattle, while the higher moorlands offer passable grazing for sheep in the summer months. Only in the North Pennines are fell ponies likely to be seen, and feral goats are occasionally spotted in the Cheviot Hills. Other mammals that can be seen include foxes, badgers, hares and rabbits, along with small rodents, or bats in the evenings.
The heather moorlands of the Pennines are managed for grouse-shooting, which involves the control of ‘vermin’, meaning anything likely to affect the numbers of grouse on the moors. Red grouse are dominant, but there are small areas in the North Pennines with black grouse too. The plaintive piping of the curlew will be heard on the moors, while snipe may be flushed from cover. Lapwings are notable in high pastures, usually when trying to distract walkers from their nesting sites. The reservoirs and bog pools attract all manner of wildfowl and waders, and it is not uncommon to find raucous colonies of gulls breeding on the high moors, far from the sea. Emperor moths are also notable on the high moors.
Reptiles include common lizards, adders and grass snakes, although these are rarely seen. Amphibians include frogs and increasingly rare newts, while the native white-clawed crayfish is under great threat from competition and disease introduced by non-native species.
A well-camouflaged adder on a heather moor adopts its strike position when approached too closely
Plant life
Woodlands are rare in the Pennines, although densely planted commercial forests occur in some places. For the most part, the high Pennines feature tussocky moor grass with boggy patches of sphagnum moss. In the summer months, vast areas of nodding bog cotton give the impression of snow-covered slopes. There is rather less heather than most people expect, and much of it has been managed to provide a habitat for red grouse. The dominant species is ling, although there are occasional areas of bell heather. Heather is burnt on a rotational СКАЧАТЬ