Sheffield’s rock of ages

Landscape of the Mayfield Valley walk : Peter Kennett discussing the Mayfield Valley using  a field sketch
Landscape of the Mayfield Valley walk : Peter Kennett discussing the Mayfield Valley using a field sketch

PETER Kennett has many years experience of trying to make people enthusiastic about geology in the face of the more cuddly areas of natural history.

“In my book geology is extremely important,” he says to 20 well-wrapped rock watchers. “Everything depends on it, is built on it and grows in it.”

It’s a chilly Saturday morning at Forge Dam and Friend of the Porter Valley Peter is leading a walk looking at the landscape of the Mayfield Valley (and a bit of the Porter too).

Peter was a geology teacher for over 30 years, and is still keenly interested in the subject, which is often sadly neglected by the public and by the Government in their landscape policies, he says.

He launches into a condensed description of the various rock types to be found around the Porter and Mayfield and produces a bright red and yellow model of the surrounding landscape. “My sixth-formers made this 40 years ago out of wet paper and Polyfilla,” he says, proudly.

The rocks of the area are up to 300 million years ol, and reveal the times when Ranmoor and Fulwood were under the sea or beneath a tropical forest on a forgotten continent, which, says one of Peter’s leaflets, has migrated northwards at ‘the rate at which your fingernails grow’.

In an attempt to emulate modern Attenborough-style nature broadcasting, Peter pulls out a piece of shale he found earlier.

“Lets see if we can see anything no-one has ever seen before,” he announces, handing the rock and a blunt knife to an onlooker. He demonstrates how to deftly peel off layers of shale, and a fossilised view of life many millions of years ago is revealed next to the Forge Dam cafe ice cream window.

“There it is. A Dunbarella, a kind of bivalve. Nothing to write home about,” he sighs. “But it does show how sea covered this entire area, when there were no hills and valleys.”

Peter and FOPV colleagues have written at some length about the landscape, history and geology of the Porter Valley area and their findings are summarised in several leaflets available at Forge Dam cafe.

Peter suggests the public could get hold of these, follow the landscape walk and try and work out themselves from one of the viewpoints how the different rocks have influenced the landscape and what goes on there.

“Sheffield is unique in a way with so many rural bits fingering into the city. It was used by industry, with a bit of iron and coal and the water power, and there’s quite a bit of all that left around here if you use your eyes. And to let it all lapse would be a tragedy.”

Saturday’s walk aimed to offer a glimpse of all this – the Friends have a series of such events to raise interest in the area.

After a brief stop at the silted-up Forge Dam, the walkers climb uphill towards Fulwood to see a 400-year-old oak tree and to learn how holly was used as winter fodder at ‘holly haggs’.

At the top near School Green Lane there’s a view of ancient irregular field systems, possibly going back 2,000 years. From the viewpoint, Peter explains how the many large stones in the valley probably slid down from rock above during the summer melt of the Ice Age.

He asks his students for the day to have a look at the stone wall in front of them for a stone he overlooked in an earlier search.

They find a rounded fragment of quern stone, used in the ancient past to grind grain into flour.

“It might have taken a woman four or five hours to grind enough flour for her family,” he says.

On the way back, he stops near the confluence of the Mayfield and Porter near Clough Lane, with a warning that the actual meeting point is in a small thicket in the middle of an almost impenetrable bog, so perhaps best to take his word for it.

Much has been learned by the 20 mature students but there’s clearly lots more to see on the sandstones, shales and grits of the Porter Valley.

“It’s often overlooked but the influence of geology on the landscape underlines everything,” says Peter.

lwww.sheffieldportervalley.org.uk.

lDam clean-up drive, page 19.