Cleaning, geophysics and a trench extension
Dig Diary – Day Two
Tuesday, June 29, 2021
As regular diary readers will know, the first two days back on site are usually taken up with “housekeeping” – tidying up the trenches and the archaeology within ready for work to begin in earnest.
Today was no different. But after almost two years under covers, that clean-up was sorely needed. There was vegetation to remove, wall lines and paving to clean, and sections to freshen up – some of which required some remedial work after the excavation hiatus.
So it was heads down and trowels out. The team handled it with aplomb, prompting site director Nick to comment that he hadn’t seen the eastern section of Trench P looking so good.
The finds so far have included flint, pumice and, in the vicinity of Structure Ten, more animal remains.
While the cleanup was ongoing, over at Trench J some of the questions surrounding Structure Thirty-Two – the later building that sits on top of the south-western end of Structure Five – were being probed.
Gordon Higgs and Mark Williams carried out resistivity scans of the areas to the north-west and south-west of Trench J to see whether geophysics could give some indication of the extent of Structure Thirty-Two, particularly how far it extended outside the edges of the trench.
The results were complex. Although the northern boundary wall (aka “the Great Wall of Brodgar”) showed up beautifully, the situation regarding Thirty-Two was not so clear-cut.
The recent prolonged dry spell in Orkney may be responsible.
Resistivity measures the resistance to an electrical current passed through the ground. The amount of water present in the soil is affected by some archaeological features. A wall under the surface, for example, means there’s less soil to store moisture, so it will show up as an area of high resistance.
A ditch or pit, on the other hand, can store more moisture for longer, giving a lower resistance.
What’s that got to do with Orkney’s recent dry spell? Well, if the ground is too dry there’s no water to affect the electrical current, which will impact the resistivity results.
While supervisor Paul is going to study the geophysics data further, plans are already afoot to open up a new extension to the north-west of Trench J tomorrow. This will let us see whether Structure Thirty-Two does extend beyond the trench edge or whether it is just a solitary wall section raised on the remains of Structure Five.
Watch this space for details.
Meanwhile, tomorrow, Wednesday, is also the first day we open to the public, so we’re looking forward to welcoming you all back on site.
As we’ve explained previously there’s a few changes this year, due to Covid, so if you’re planning a visit, check out our guidelines here beforehand.
We hope to see you soon.