The rocks of Bilsdale were laid down about 180 million years ago during the Jurassic period. The area was covered by sea and located closer to the equator. Conditions varied as the sea level changed. Sometimes the land rose above the sea and was covered in dense foreasts. Geologists have identified 3 distinct phases, the Lower, Middle and Upper Jurassic periods.
These flat sea beds were eventually pushed up and twisted when the Alps were forming in Europe, so they now tilt gently to the south. The continuous process of erosion has removed more than 3,000 ft of rock, so the streams in the northern part of the dale now cut into the Lower Jurassic lias shales. The surrounding dale and moors consist of layers of Middle Jurassic rocks and, to the south, the climb up Newgate Bank takes you onto the Upper Jurasiclimestones and sandstones.
Within the Middle Jurassic layers are the ironstone, jet and alum deposits which have been extensively mined and formed the basis for early industry in the dale.
During the last ice age which finished about 12,000 years ago, the ice sheets did not cover the moors. Lakes formed between the ice and the northern scarp face so melt waters regularly flowed down Raisdale and Bilsdale creating the gaps between Live Moor, Cringle Moor, Cold Moor and Urra Moor. As the water flowed down Bilsdale a V-shaped valley was created. Springs emerged along the valley sides between the Lower and Middle Jurassic rocks and eroded the valley sides further to produce the present U-shaped valley.
As the ice receded, trees and vegetation spread over the area and changed as the climate warmed. The moor tops were heavily forested, and the valley bottons were wet and boggy. Bronze Age man created tracks across the moors and cleared the forests. This lead to severe erosion and the formation of the peat.
With the development of the heather moors, the area became popular for grouse shooting and the moors are now managed to support this.
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Published: 13 2016 (Updated: 24 2017)