Jackson, Ian. Cumbria Rocks — 60 extraordinary rocky places that tell the story of the Cumbrian landscape. Newcastle upon Tyne : Northern Heritage, 2022.
The richly illustrated and accessible book series of Cumbria, Northumberland and Durham Rocks are available to purchase from Northern Heritage.
Theme: Rivers, seas and life
5 Holmepark erratics and Woodbine mudstone band. Take the bridle path from Holme Park Farm onto access land of the fell. It’s a very pleasant 2 kilometre return walk
Just after you cross into Cumbria heading north on the M6, you’ll maybe notice a prominent pale grey hill to the east. It’s called Holmepark Fell and you might also see it’s got a notch across its top.
The pale hill is limestone but the notch is (was) a rock layer called the Woodbine Shale. Climb up the hill and you won’t find the shale; it’s hidden by limestone scree. Shale and its close relative, mudstone, are the invisible men of field geology. You know they exist; the quarry next door has excavated them; boreholes prove they are there; and you sometimes catch a glimpse in a fresh cliff. But in the landscape shales rarely reveal themselves. Reason: shales are easily eroded. They were once mud and while they may have been compacted, they are the soft option. Limestone and sandstone are much harder, they resist erosion and stand proud in the landscape. Shales give us the depressions and valleys, the negative features. Yet shales make up a lot of the rocks in Cumbria, especially those from the Carboniferous Period. At Holmepark Fell the Woodbine Shale has a thickness of around seven metres but the notch you can see is where it used to be. Time and weather have worn it away. But the view from Farleton Knott is well worth the walk.
Shales are in the public eye, controversially. Natural gas can be found trapped in tiny pores in shale. The gas comes from the decomposition of ancient plants and animals and can contain 70 to 90% methane. The technique used to extract shale gas is called fracking; drilling boreholes and artificially fracturing the rock to release the gas. The Bowland Shale, which stretches underneath much of Lancashire and Yorkshire, is a Carboniferous shale like the Woodbine Shale, but it is one hundred times thicker and is rich in organic material. It is a potentially valuable prospect for gas production and that means in these times of rising energy costs a contentious debate might re-start.