Monday, 14 May 2018

A Geology Field Trip to Green Moor



A well marked public footpath in Green Moor

After undertaking a preliminary reconnaissance of Green Moor, in preparation for a field trip with the Sheffield U3A Geology Group, I felt that the preparation for this event had gone well, especially since there was help from a local resident to explain the industrial history of the area.

A long stretch of stone walling built with Greenmoor Rock

On the day, our way to Green Moor from Wortley was blocked for essential works and, with a badly signposted road diversion then taking us all around the houses, we eventually turned up 10 minutes late at a designated meeting point that had become infested by wasps.

At the meeting place in Green Moor

Introducing the group to the physical characteristics of the Greenmoor Rock by examining nearby dry stone walling and roofing tiles - noting its thinly bedded and laminated nature - we briefly stopped at the new Stoneway Manor housing estate – where its history of Geological Conservation was briefly described.

The Old Pump House at Stoneway Manor

Moving westward along Green Moor Road, the old school provides a good example of the differential use of the Greenmoor Rock – with the infrequent massive beds of sandstone used for its dressings but with the basic walling using the thinly bedded stone. A little further along the road, there is a good opportunity to observe the geomorphology of the Don Valley where - strikingly - the gradient of the landscape reflects the dip of the underlying rocks.

Hunshelf Hall

Briefly pausing at Hunshelf Hall, where the Greenmoor Rock contrasts strongly with the Welsh slate that has been used to re-roof it a century later, the group continued along a surprisingly busy narrow lane to Don Hill Height – where there are good views of the escarpment, the steel making town of Stocksbridge and the Millstone Grit moors of the Peak District National Park.

Stopping to admire Hunshelf Hall and its fine eucalyptus trees

The old road stone quarries here are very impressive, with the very irregular bedding being emphasised and the poorly cemented Greenmoor Rock leaving distinctive orange coloured hollows. At the top of the quarry, the dry stone walling seamlessly merges with the natural rock.

The Greenmoor Rock at Don Hill Height

Having had a good look at this excellent exposure of Greenmoor Rock, the next stage of the walk provided an unexpected obstacle. In April, the paths along the escarpment are well defined but, in July, a large section of these were covered shoulder high in bracken.

Bracken at Don Hill Height

A path through this was soon found and the group stopped to discuss the geomorphology and landscape that we could see around us, especially the contrast between the bracken and gorse, which grows on acidic soils on the Greenmoor Rock, and the grass that grows on the shales.

Greenmoor Rock used as a building stone

Following an established path that runs along the escarpment, there are further examples of dry stone walling and the occasional agricultural building and several very large blocks of stone - with extremely fine ripple marks - can be seen at the Isle of Skye Quarry.

Blocks of ripple marked Greenmoor Rock at the Isle of Skye Quarry

The waymarker here couldn't be put to good use - due to the poor visibility on the day - and so we just carried on with our walk back down to the village, where we encountered a few Hebridean sheep and the remains of a trackway that was once used for transporting stone from the Isle of Skye quarry.

A waymaker in the Isle of Skye Quarry

Moving on to the Green Moor Delf quarry, which has now been designated as a RIGS (Regionally Important Geological Site), the rock exposure here provides an excellent example of large scale cross-bedding and foreset beds. Although actively managed by Hunshelf Parish Council, the rapid growth of vegetation at sites like these provides an ongoing problem of maintenance, which can lead to complete obliteration of exposures, as at Boston Park in Rotherham.

The Green Moor Delf Quarry

We finished off our walk at Ivy Millennium Green, where we took a late lunch break before exploring the Old Pump House, which was once used to provide essential water to the village of Green Moor.

Ivy Millennium Green in Green Moor

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