13 July 2008

High Force

High Force is a waterfall on the River Tees, near Middleton-in-Teesdale, Tees Valley, England. Despite popular belief, it is not, at 20 metres (70 feet), the highest waterfall in England: Cautley Spout, in Cumbria's Howgill Fells, is almost 180 metres (600 feet) high; and Hardraw Force, in North Yorkshire, has an unbroken drop of 30 metres (100 feet).

High Force is, however, undeniably stunning, with the whole of the River Tees plunging over a precipice in two stages. In former times flooding created two separate falls but after the completion of Cow Green Reservoir in the upper dale this seldom happens now. Also, in harsh winters the falls would freeze, creating cathedral-like ice formations. Again, this very rarely happens nowadays, perhaps due to climate change.

High Force is formed where the River Tees crosses the Whin Sill - the rock system followed by Hadrian's Wall. The waterfall itself consists of two different types of rock. The upper band is made up of whinstone, a hard rock which the waterfall takes a lot of time to erode. The lower section is made up of carboniferous limestone, a softer rock which is more easily worn away by the waterfall. The wearing away of rock means that the waterfall is slowly moving upstream, leaving a narrow, deep gorge in front of it. The length of the gorge is currently about 700 metres. The bedload (rocks that the river is carrying) is mainly composed of large boulders, which are rolled along the river bed. Upstream of the waterfall, the river is narrow, but afterwards, it widens and begins to meander.

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