Teesdale
Coordinates: 54°32′42″N 1°55′37″W / 54.545°N 1.927°W
Teesdale is a dale, or valley, of the east side of the Pennines in County Durham, England. Large parts of Teesdale fall within the North Pennines Area of Outstanding Natural Beauty (AONB) - the second largest AONB in England and Wales. The River Tees rises below Cross Fell, the highest hill in the Pennines at 2,930 feet (890 m), and its uppermost valley is remote and high. The local climate was scientifically classified as "Sub-Arctic" and snow has sometimes lain on Cross Fell into June (there is an alpine ski area Yad Moss).
Unusually for the Pennines, rock of igneous origin (the Whin Sill) contributes to the surface geology and scenery of Teesdale. Around 295 million years ago upwelling magma spread through fissures and between strata in the earlier Carboniferous Limestone country rock. As it cooled (an event which is believed to have lasted 50 years) the rock contracted and caused itself to split into vertical columns. The heating of the limestone above the roack also caused it to be turned into a crumbly marble known as Sugar Limestone.
Economic deposits in Llandovery rocks include soft shales that were previously worked to be used as slate pencils.
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