Welcome to another in our Living Lomonds archaeology blog posts. Firstly, apologies for the gap since our last post. A whole lot of fieldwork has been happening out on the hill since June and we are fast approaching the first of our Living Lomonds Big Digs. This starts at East Lomond Hillfort in Fife from Monday 15th September until Sunday 5th October. Take a look at our website for more information about how to visit: the-living-lomonds-big-dig-2014-east-lomond-hill. I’ll be bringing you updates about the digs progress every other day – so stay tuned for more regular posts!
We’ll bring you more about the dig plans with the first posts, but the current little entry is mainly about geophysics: what it is all about and news about the fascinating surveys that LLLP volunteers have been undertaking this year. These include the first geophysical survey at East Lomond Hillfort completed by our brave and dedicate teams of volunteers; the results of which have informed planning for our community excavation at the fort.
Seeing Beneath the Soil: Archaeologists and Geophysics
Geophysics covers a range of scientific techniques that were first developed by geologists to investigate physical characteristics of the earth’s strata (layers of rock and soil deposits) that are buried deep beneath the surface. Archaeologists began to experiment with these techniques from the 1960s/70s. Techniques such as seismic, ground penetrating radar and electrical resistance were used to investigate archaeological remains at shallower depths. Archaeological geophysics is often refered to as ‘shallow geophysics’ for this reason. These shallow methods can still pick up deeper geology sometimes creating a challenge for the archaeologists. The different forms of survey and devices can each provide different types of information about deposits and structures buried under the turf. Since the 1990s tailor-made survey kit have been commonly used by professional archaeologists in all walks of life to investigate what might be buried out of sight; from commercial units to university researchers. In 2008 a study by English Heritage recorded that about 26% of all development management archaeology work (part of Local Authority planning processes) included some kind of geophysical survey to evaluate proposed development sites.
Despite this geophysics still has a bit of a reputation among some archaeologists as being a unreliable, particularly in Scotland, which has more than its fair share of igneous geology that can particularly affect magnetic based surveys. This has led some naysayers to declare that “geophysics doesn’t work in Scotland”, which is often preceded by a sharp intake of breath between the teeth or a range of tutting noises. Happily such negative views are pretty much nonsense and expounded by those with a fairly limited misunderstanding of how geophysics works, what it actually does for you and what it should be expected to do.
Basically geophysics simply provides a combination of information about the physical attributes of buried deposits and (now this is crucial) spatial information about those attributes (ie. where different readings are located on the ground). Figuring out exactly what geophysical readings are actually telling you about the archaeology that is buried under your feet is the tricky bit. This ‘data interpretation’ is something of an art form, the success of which is largely down to the experience and skill of the archaeologist who is interpreting the data and the extent of good quality archival and mapping research that has been done about a target site beforehand. Admittedly, this subjective factor in geophysics interpretation can occasionally led to embarrassing moments for the unwary or unlucky surveyor, when a juicy looking anomaly turns out to be something non-archaeological or nothing at all. Common problems occur if data has been over-processed or a not enough background research has been done about a site or made available to the surveyor. In practice there are generally two stages to any survey: recording readings out in the field using a device in a systematic survey grid and then the data processing and presentation. Conventional data results like resistance survey and magnetometer (the ones you’ve probably seen in action on re-runs of Channel 4’s Time Team) produce results in the form of 2D data plots, usually displayed as some form of grayscale pattern. These show different levels of readings as black, white or grey coloured makings within a square grid. You also get ‘3D’ data from certain kinds of radar surveys and tomography, all of which provide information from different depths and so can be very useful for archaeologist.
The Living Lomonds Landscape Partnership has undertaken survey at East Lomond Hill. Here is a link showing the location where the survey was carried out around the site of an Iron Age and Pictish hillfort. Resistance and magnetometer surveys were undertaken to look for settlement or industrial activity with a focus on the southern shoulder of the hill where an outer annexe from the main fort rampart my enclose the part of the site. Here is the resistance results from a ladder of survey 120m north to south and 20m wide:
A circular low resistance anomaly near the bottom of the plot looks like we may have found an ancient building of some kind. This could be a Iron Age roundhouse or hut circle or a later Pictish cellular buildings. We’ll found out soon as we’re about to dig it. Whatever this anomaly may turn out to be, the low resistance readings suggest it more likely to be made of turf or soil walls rather than stone slabs for instance. Its a great find if we can prove its the real deal. We’ll see… watch this space for more news.
Bye for now.