Saturday, 29 June 2019

A Reconnaissance of Hob's House

Solitary corals in the Hob's House Coral Band

During March 2019, I investigated Selby Abbey, mediaeval churches in the villages of Baslow, Stoney Middleton and Silkstone, as well as visiting Poole’s Cavern in Buxton, and I finished off the month by assisting with the reconnaissance of Monsal Dale – in preparation for the next day out with the Sheffield U3A Geology Group

The geology around Monsal Dale

The plan was to firstly investigate Hob’s House, a site that is of interest to geologists for its landslips and the fossils that it contains. Secondly, we would then try and find the basalt that is marked on the British Geological Survey map, as well as identifying other points of interest on a circular walk of more than 8 km. 

A view down down Monsal Dale from Monsal Head

Arriving on a cool Saturday morning, when a mist still hung over the various valleys that we encountered after leaving Sheffield, we easily found a parking space on the road from Little Longstone and started off at the usual time of 10:30 am. 

A view of Hob's House from Monsal Head

So I was told by my colleague, he had been to Hob’s House with the group before but, when walking down the well-trodden path from Monsal Head to the valley bottom, a local explained that a high level path had long become overgrown and that the Duke of Devonshire had been erecting fences to prevent access to Hob’s House, where it was considered unsafe. 

Vegetated scree below Hob's House

Not being able to see any kind of path by the time we had reached the large weir on the River Wye, we attempted to scramble up over a heavily vegetated scree slope, but both of us had potentially injurious slips in the attempt and had to retreat. 

A barbed wire fence below Hob's House

Our next effort, also by an undefined path, took us to a barbed wire fence that had been previously described to us and, by this time, I was beginning to curse my companion who casually slipped under this fence. Whilst I admired his tenacity at the age of 70, a risk assessment for undergraduate geology students would have been rated as high and, for a group that has membership of an average age of 70+, it would have been well off the scale. 

A cleft in the limestone at Hob's House

Finally arriving at Hob’s House landslip, which comprises a series of very large blocks of Monsal Dale Limestone Formation separated by wide clefts, I have to admit that the climb was well worth it, but we agreed that another route to the site would need to be found for the group.

Chert nodules and solitary corals

Although the rough, blocky terrain of the scree need to be carefully traversed, the irregular, nodular beds of chert and the Hob’s House Coral Band are spectacularly exposed here. The latter is about one metre thick, with a lower leaf rich in the small colonial forms Diphyphyllum and Lithostrotion and an upper leaf with large solitary corals, particularly Dibunophyllum.

The Hob's House Coral Band

Unlike those most often seen in the Carboniferous limestone, the fossils here have been silicified and differential weathering between them and the surrounding limestone has left the corals standing proud of the surface, with the fine details exceptionally well preserved. 

A solitary coral

Having had a good exploration of the various rock faces, a large rotated block of limestone, and the scree slope above Hob's House we then set off to find our way back down to the main path from Monsal Head. 

A rotated block and the scree slope above Hob's House

Although not very well defined, it was obvious from disturbed vegetation that the route we followed was used by others and, when later eating lunch in the valley below, we saw a few people in the area where we had been less than half an hour earlier.

The start of the route down to the valley floor