Wednesday 28 December 2022

Is this year’s tumultuous weather set to become the new ‘norm’ ?


The National Trust has warned that this year’s tumultuous weather is set to become the new ‘norm’  The Stonehenge and Avebury WHS are thought to be at risk from climate change, so it is of interest here -

We hear a lot about climate breakdown, that our climate is getting more unpredictable and tumultuous. We can survive and thrive in nearly any climate if we can plan and prepare for it from the arctic to the equator, from deserts to rainforests. But instability and uncertainty is dangerous. So is it getting more disorderly?

To check if any increasing instability was evident in England  I thought a simple, quick and dirty way would be to compare the annual, and each season’s, temperature and rainfall using the long running Hadley Centre Central England Temperature (HadCET) dataset  and HadUKP, the UK regional precipitation series available from

My method was to compare the differences between years.

For instance the mean spring temperature in 2020 was 9.9°C, in 2021 8°C, and 2022 10.1° so the differences are  -1.9°C and 2.1°C.   I charted out the differences from 1963.

Wow, the swings are getting larger. English spring temperatures are getting less predictable.

So, I looked at more of the data.

Here’s the mean spring temperatures from 1904 – 1963:


Huh? That looks the same as the 1963 – 2022 chart.  Let’s overlay them to see:


So, spring temperature got more unpredictable from 1904 to 1963 and then the pattern repeated from 1964 to now.

What is going on? I don’t know but whatever it is it isn’t unprecedented.

 Just eyeballing the rest of the data graphs for the other seasons, years and annually I couldn’t spot any other repeating patterns either for temperature or rainfall. But torturing it with statistical analysis may reveal more. I hope someone with the skills does so.

  Another surprise to me from the series is how related the Min and Max series are. It appears that the temperature band is narrow, is it self-regulating?  A plot of spring temperatures shows: 

 A simple plot of Maximum temperature minus Minimum shows this over the whole period:

Sometimes very simple analysis is all that is needed to answer a question.

Friday 23 December 2022

Mesolithic Machans

Yesterday the Mesolithic tree-throw and post holes were showing up well with grass mown and it reminded me to record my belief that there may have had been a practical purpose. 

If you are ever to try a spot of big game hunting, I haven't myself, I am assured that the Cape Buffalo is the most dangerous beast to hunt. I imagine Aurochsen were similar. They don't take kindly to being wounded and a couple of tonnes of beef behind some horns travelling at speed intent on revenge is best avoided. Using only spears and arrows kills would not have been quick and easy. 

Deer hunters in our local woods still use high seats, not so much to avoid the danger, as to be out of sight and smell of the prey and have a better view and platform to operate from. 

In India and south Asian countries, such platforms, in trees and where trees were absent on poles, are called "Machans". Thankfully they now more often used to photograph big game from than for shooting.

David Saunders* in his excellent studies on prehistoric cattle movements touches on the roles the posts may have played but doesn't, I think, suggest them as machans. So combining a sketch from E P Stepping's Diary of a Sportsman Naturalist in India and a photo of the post holes let me supply a suggestion of how the posts alongside a natural funnel for the beast may have been used.
*Saunders, David. The Cursus Enigma: Prehistoric Cattle and Cursus Alignments. Austria: NIELSEN BOOKDATA, 2021.

Wednesday 21 December 2022

How many original entrances did Durrington Walls have?

 It seems surprising that the number of entrances that Durrington Walls originally had is uncertain.

1, 2, 4 and even 3 have been suggested.

Model from Gaffney V, Neubauer W, Garwood P et al (2018) Durrington Walls and the Stonehenge Hidden Landscape Project 2010-2016. Archaeological Prospection. 25(3): 255-269.

"Durrington Walls is a large oval henge, classified as a type 2 henge (Piggott 1939), with an internal irregular ditch and external bank, and with two entrances known, to the east and to the west (Wainwright and Longworth 1971, 1), although Parker Pearson et al. (2007) suggest four entrances."
Higham, R., & Carey, C. The Durrington Walls Sarsen Burial relocated and reconsidered. The Wiltshire Archaeological and Natural History Society Magazine, 112, 74-84.

"It was not possible to determine the presence or absence of the assumed north-west entrance in the bank/ditch as there is significant metallic noise at the surface here. Similarly, it is not possible to establish the nature of the apparent breaks on the north and east sides due to the presence of the old and new main roads cutting through the earthworks at these points."
"There appears, for example, to be no certain evidence for a north-west entrance. The air photograph used by Crawford (1929, 54-6, pl.III) might indicate such an entrance, but this also seems to show a gap in the ditch on the east side of the enclosure which certainly does not exist. The land surface in the area of the supposed entrance is steep and very uneven, apparently heavily-disturbed, suggesting relatively recent modification of the scarp slope possibly to create an entrance ramp into the field within the enclosure area, which might account for the ‘gap’ observed by Crawford. The geophysical survey data (GPR and FDEM) are ambiguous, but there is certainly a suggestion that the ditch is continuous (see fig. 15). It is possible, therefore, that the Durrington Walls henge enclosure only had a single south-east entrance." Gaffney et al 

So the South -East entrance is certain, it seems to be ceremonial and aligned to the Solstice.

The North West one opposite seems to be becoming less certain, the area was used as a rubbish dump so it is hard to survey but there doesn't seem to be any evidence it was there.

 "the vexed issue of the north-western entrance to Durrington Walls henge becomes significant. Initially postulated by Crawford (1929, 54–56, plate III), the entrance is complicated by the presence of a large scarp that lies between the bank and ditch, and which must pre-date the enclosure (Gaffney et al2018, 10). The area associated with the postulated entrance is very steep, uneven and heavily disturbed and the geophysical survey data from the henge is ambiguous regarding whether an entrance actually exists at this point."   Gaffney, V. et al. 2020 A Massive, Late Neolithic Pit Structure associated with Durrington Walls Henge, Internet Archaeology 55.

The North and South entrances are hard to interpret as the old road went through them. Talking to archaeologists the feeling is that the north one probably is the least certain and is probably more a modern agricultural access to the interior. The South entrance has more features such as a curve to the ditch which hint it may be original. 

To answer the question, I think 1 is certain and 2 probable, but not the traditional two. I think as at Stonehenge there was a ceremonial entrance and maybe a more functional one to the south. 

Saturday 3 December 2022

The Stonehenge Sarsens didn't float down the Avon

The route that the great sarsens were brought from the Marlborough Downs to Stonehenge is still debated. This blog was started to investigate it and it is still of interest.

I am using 40 tonnes as the maximum weight of an untrimmed sarsen that was moved. The raft or sledge it was moved on then adds to this weight.

The idea that they were brought down the River Avon from Upavon to Amesbury is still popular despite the impossibility of it.

The River Avon we see now isn't the same as it was in Neolithic times, the main difference is that it has historically been dredged, over-widened and impounded in many places due to past river management.

It would have been a multichannel meandering stream in a marshy valley bottom with trees and bushes growing over and in it.

1) They weren't slid on the frozen river. 

The River Avon is largely fed from ground water along its route, water that is referred to as warm during the winter as it stays at near constant temperature all year round. The river doesn't freeze solid and according to Gold's Formula the ice would need to be over 500mm thick 

The River at Amesbury has a normal maximum depth of 700mm and is usually half  of that, and at Upavon it is a lot less.

Photo from Pennsylvania Lumber Museum 

2) They weren't loaded onto rafts and floated down.

To float 40 tonnes of stone  40 cubic metres of water must be displaced. If we had a weightless box to load the stone on it would need to be 4 metres wide, 20 metres long and 500mm deep, the depth of the river being a limiting factor here.

A wooden raft made of logs would need to be much larger. Wood has a specific gravity of 500 - 800 kg per m3 . The photo shows how only half of a  log raft is out of the water. At the lightest end the raft would need to weigh another forty tonnes to displace enough water, at a more realistic weight for hardwoods of 750kg/m3 it nearly 100 tonnes. A forty five meter by five meter wide raft at 500 mm deep. The river is not big enough.

Only by using hollowed logs or canoes could the weight and size of the raft be reduced but would they be strong enough for the massive stones?

Dragging heavy stones through an overgrown bog didn't happen, they went overland away from the river.