Thufur

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A very cold night and day

As part of our 10 Tors training, The National Trust Wild Tribe and Torquay Boys Grammar School teams, camped near Foggintor on Saturday night and then spent Sunday walking across the moor back to Okehampton camp.

It was so cold putting up tents on Saturday at dusk …. everyone was in their tents and sleeping bags by 8pm. It was one of those night when it seemed that you were awake all night – sleep seemed a luxury which was just out of reach. I was warm most of the night but when the wind got up and battered the tent you could feel a cold breath of air fill the tent and pivot the temperature towards the uncomfortable. I think everyone had similar experiences but fortunately nothing worse.

Foggintor
The first team had left camp by 6.30am and all were on their way by 7. We left camp at dawn in the shadow of the derelict mining building

BreakfastNext stop was Fox Tor Cafe for breakfast – a perk of the job if you are check pointing teams. From here we dropped off two of the team at Holming Beam to shadow various teams along their route.

Tavy CleaveNear Lane end – where we met a couple of teams – out of the wind with a glorious view over to Ger Tor and Tavy Cleave

We then made a detour back to Holming Beam to collect one of our 55ers who had fallen waist deep into a bog – it wasn’t a day for ‘bog falling’ as the wind chill on the high moor kept the temperature close to or below zero all day. Emergency plans worked perfectly – tents were erected, hot drinkers were made and our two ‘shadowers’ brought the now warmed up 55er back from Rough Tor.

Yes Tor
We now had a bit of time on our hands to we climbed Sourton Tor and got incredible views across to High Willhays, Yes Tor and West Mill Tor (note the peri-glacial ‘Thufur’ bumps in the foreground – I have written about these before – see here)

Check pointingThen out to Oke Tor from Rowtor (minibuses left at Okehampton Camp!!) – Pete, Mark and Tony scanning the horizon, checking texts and phoning teams – I just take the pictures ….

East MillThe sun beaming through the clouds over East Mill Tor (in the fore ground) with High Willhays in the distance

Winter TorAfter completing our  appointments with our teams we headed back to Rowtor – the sunlight catching the hillside above Cullever Steps – with Winter Tor on the right, Higher Tor in the middle and the start of Belstone Tor on the left.

Sunset-2

Back at Rowtor the sun was getting ready to set – we weren’t quite done yet as two teams were still ‘practicing’ their navigation skills …. best done in February rather than May but it meant they were a bit late back – all part of the fun and no harm done.

Well done to all the teams, leaders and helpers – it was a challenging couple of days thanks to the weather but that to be honest is all part of the 10 Tors’ tale. Wonder what weather we will get the next time we are out?

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What are these bumps on the moor?

Over the years on our 10 Tors training expeditions we have come across the bumps on the north  and north west side of the moor.

Thufur1Bumps on the moor below White Tor

Thufur2Cattle giving an idea of scale

A couple of weeks ago Dave Berry took these photos and sent them to me in the hope I could find someone who knew what they were. As a result I sent the pictures to the archaeologists and nature conservation advisors in the National Trust and the Dartmoor National Park Authority.

Are they ant hills? Something archaeological like pillow mounds?

Well within hours Jim Parry the NT archaeologist has consulted with Janet Lister the NT nature conservation advisor and ….. concluded these bumps were of periglacial origin i.e. on the edge of areas where the glaciers in the last ice age got to and therefore areas which were subject to seasonal freezing and thawing.

A bit of googling and Jim found the answer – thufurs

‘A special form of cryoturbation is represented by earth hummocks or thufur, they are vegetated oval mounds with heights of 30 to 50 cm. Earth hummocks develop because of local patchy freezing of pore-water in the active layer, yet no pure ice core forms but a small proportion of the soil freezes. This core of frozen ground causes moisture migration towards it, concurrently causing a small scaled displacement of soil material in the same direction. Frost heaving leads to the development of a small mound, and as the freeze/thaw processes re-occur many times, this displacement is amplified.’

Abb15kryo‘The picture above shows the internal structure of a hummock: an accumulation of humus can be discerned. As humus has a high capacity for storing water, it leads to the development of more ice in the earth hummock. Often being frozen, the decay of the organic material is slowed down, which in turn raises the amount of humus in comparison to unfrozen inter-hummock areas. The thick layer of humus also has an insulating effect, thus the formation of ice and its preservation are positively affected.’

Thufur