On the 25th and 26th of October Earthsound have carried out a number of geophysical surveys for Fingal What Lies Beneath: Fingal Geophysical Survey Project (Phase II)

Project: Brownshill Portal Tomb

Location: Carlow

Year: 2018

So this is our first post of 2018! We’ve had a grand start to this year. Surveyors headed up north for a couple of weeks to undertake two separate surveys around two churches for research projects, and also paid a brief visit back to Meath. On top of these, some research projects from last year were wrapped up.

Panorama of Brownshill dolmen and earth resistance survey (Photo: C. Hogan)

This week Cian and Ciarán headed down to County Carlow to carry out a survey on the land surrounding the impressive and imposing portal tomb at Brownshill. The Neolithic monument is situated in rolling lowlands and positioned on the northeastern side of a small hillock. The capstone is reputed to weigh up to 150 tons and is thought to be one of the largest erected in Europe.

Brownshill dolmen banked in snow (Photo: C. Davis)

Earthsound were commissioned to investigate the area around the monument using an earth resistance meter. We started work on Monday afternoon, and on Tuesday morning members of Carlow Historical and Archaeological Society visited while work was ongoing. A small group were given a presentation on geophysical surveys, and following this assisted in collecting a portion of the resistance data in front of the dolmen.

Work had to be cut short due to the arrival of the ‘Beast from the East’! While the sun was shining during the Society’s visit, when they left so did the good weather. Snow started falling soon after, and coming up to the final grid of the day, a blizzard set in. Quite an experience doing a resistance survey in those conditions! On Wednesday morning, several grids of data were taken in a winter wonderland, with snow coating the ground and the dolmen, and the sun shining brightly. With icicles hanging from the van, the surveyors headed back West ahead of predicted worsening weather.

Cian talking with members of Carlow Historical and Archaeological Society (Photo: C. Davis)

Earth resistance meter and dolmen (Photo: C. Hogan)

Members of Carlow Historical and Archaeological Society collecting earth resistance data (Photo: C. Davis)

Almost at the end of the grid!! Ciaran surveying during a blizzard (Photo: C. Hogan)

Cian surveying before the arrival of the ‘Beast from the East’ (Photo: C. Davis)

And after – Cian in the snow with earth resistance meter (Photo: C. Davis)

Seasons greetings to all!

It’s come to that time of year again when the work is getting quiet and everyone is preparing for a new year. This year has been full of change and excitement for those of us at Earthsound – people coming and going; impressive sites visited; and wonderful data collected.

The year kicked off with a two-month stint down in the county of Cork. Taking up residence in Ballyvourney (and all the while enjoying the fantastic local brews offered by Nine White Deer brewery), Earthsound surveyed the lion’s share of the long-awaited N22 route upgrade. Cork was a popular destination this year, with various members of Earthsound heading down for shorter projects throughout the rest of the year – back to Ballyvourney, Castlemartyr, Carrigaline, Blarney, Clonakilty, Ballincollig, Kinsale, Ballincollig again, Kinsale again (I think that’s everywhere!).

Ciarán and Cian metal detecting at Kinsale (Photo – U. Garner)

Foerster cart at Ballincollig (Photo – C. Hogan)

Every so often a change of scenery was in mind and we headed somewhere other than Cork for fieldwork. Following on from the stretch in Cork, a couple more surveys for the TII popped up during the year, though they were much smaller in size. A couple of days in Westmeath and a week in Laois to undertake preliminary work for road-straightening jobs to come. Some private developments took us to Meath, Laois and Dublin.

Ciarán with Foerster cart at Castle Ward, Co. Antrim (Photo – C. Hogan)

The month of May was more or less spent north of the border. Two of the surveys were for solar farm developments. At the start of the month we were north of Belfast for a job of 15 Ha. At the end of the month we were south of Belfast, undertaking one of the largest private developments we’ve worked on – 26 Ha of geophysical survey. Between these two jobs, we spent a couple of days at the wonderful Castle Ward, Co. Down – the setting for Winterfell Castle from Game of Thrones. We were investigating the landscaped gardens in order to locate Queen Anne’s house and other garden features.

Darren instructing Ursula and Ciarán on the MSP40 (Photo – C. Hogan)

2017 saw quite a shift in terms of staff at the company. Hannah Brown (now Dr. – congratulations!) temporarily joined the survey team. In April, Ursula Garner and Ciarán Davis, recent graduates of IT Sligo, joined the company – bringing it up to largest it had ever been, at six employees. During the first couple of months we had some great training days in local fields and the green at Castlebar barracks. And after seven years of surveys, Darren Regan decided it was time for a change and headed off for sunnier climes in October.

Panorama of entrance to Doon Fort (Photo – C. Davis)

Research projects were the name of the game for this year. We were back for a second round at Knocknashee Hillfort with Queen’s University. Following last year’s MS survey of the entire hilltop, this time half of the summit plateau was surveyed using Earthsound’s first in-house frame – the Earthwalker. Vinegar Hill was in our sights twice in 2017. An ERT survey was carried out early on in the year, which was was followed up a few months later by involvement in a metal detection survey. We were working closely with the National 1798 Rebellion Centre and Rubicon Heritage on this very interesting project. This year also saw the first surveys for the Heritage Council’s ‘Adopt a Monument’ Scheme (run in association with Abarta Heritage) take place. Earthsound had the delight to undertake a detailed survey of the interior of Doon Fort – probably the best survey spot in the world! We spent a week in the westlands of Donegal, paddling in and out with equipment to carry out the survey. Following this, we headed in the opposite direction to Kilfinnane, Co. Limerick. Here, we carried out the first surveys investigating the lands surrounding one of Ireland’s most impressive mottes. After several years of looking for walls in Athy, we had the opportunity to put the experience gained there to practice in Castledermot and Kilkenny. The surveys at both locations proved fruitful, with walls and ditches being identified.

Panorama of interior of Doon Fort (Photo – C. Davis)

ERT survey at Vinegar Hill (Photo – J. Bonsall)

Ursula with the EM cart in front of Kilfinane Motte (Photo – C. Hogan)

Foerster cart with Newgrange and Dowth passage tombs somewhere in the background (Photo – C. Hogan)

The year wound down with a number of short surveys here and there: a quick jaunt down to Claregalway one morning to do some work ahead of a graveyard extension; a Saturday afternoon in Dublin city centre to carry out a radar survey; and a trip to Meath in order to check out a pipeline corridor.

Wishing you and yours a Merry Christmas! And all the best for the New Year!

Be it through Channel 4’s Time Team or through homegrown heritage documentaries, people’s exposure to, and understanding of what geophysical techniques can locate has greatly improved over the past few years. Many members of the general public will have an awareness of techniques such as Magnetometry and Ground Penetrating Radar and will have at least a cursory understanding of what they are and what they’re used for. We have become used to hearing about the wonderful knowledge that the ever-developing technology employed by geophysicists can offer us about our past and this can be of enormous benefit in terms of informing people outside of the field of geophysics. However, this can sometimes lead to a somewhat distorted understanding of the constraints and limitations associated with our techniques as well as the full extent of the information which we can realistically provide about a given site.

Our Geophysical Techniques cover a wide variety of technologies from the most commonly requested and well-known methods such as Magnetometry and Earth Resistance to methods which may be used more infrequently and for very specific site types of archaeology, such as Induced Polarisation for the location of wooden trackways within peatlands. Earthsound have the capacity to avail of a number of varied techniques and, when possible, can deploy more than one technique over a given site enabling us to yield the maximum amount of information available about the archaeology which lies beneath our feet. However….

Where are you looking?

The first thing we as geophysicists need to know before we can discuss what approach or methodology to undertake on your site is its exact size and location. This is important for a number of reasons. Firstly it allows us to provide you with the most appropriate technique to find what you’re looking for. The geological composition of the bedrock of the site can heavily influence the choice of technique. Although the geological make-up of the island of Ireland is fairly homogeneous, comprising mainly of carboniferous limestone, there are many regions where the geology may have an adverse impact on a technique that the client might request. A good example is the use of Magnetometry in the northern part of the island, where a large amount of volcanic and basalt geology can severely impede the ability of Magnetometry to locate the more subtle magnetic signatures emitted by archaeological remains.

Geological dyke found in magnetometry

The above image shows a Magnetometer survey containing a strongly magnetic geological dyke located throughout the middle of the survey area (the long arcing black-and-white line running top-left to bottom-right). As you can see, the strong signature given off by the geological feature obscures all of the other ambient magnetism as well as any anomalies of potential archaeological significance.

Another reason for needing to know the location of the proposed survey area(s) is for sheer practicality. Our Magnetometer array, for example, has a span of about 4m x 3m and has a large turning circle. This, added to the fact that it can be quite heavy, can mean that a promontory fort located on a sheer slope on the edge of a cliff may be a little bit beyond our capabilities!

As with everything, we are always eager to accommodate our clients and if we feel that one technique might not be amenable to the requirements of the site, we will suggest another, more appropriate one.

What is the land used for?

Another related question is the current and past land usage of the site. One of the main things we need to know prior to survey is whether or not it is possible to move our instruments unimpeded and ensure the collection of the best quality of data possible. For example, if the land is being used for tillage or silage, we would only be able to carry out our survey once the crop has been harvested or if it is in the very early stages of growth. In addition to this, land which is boggy or poached will present difficulties for our surveying equipment, alternative methodologies may be deployed in some instances. Similar issues apply to livestock so we would request that any areas which are to be surveyed be emptied of cattle and horses in particular.

Example of unsurveyable terrain

It is also especially important to know whether or not there has been a history of dumping or burning at a site. If a given area has historically been used to dispose of waste (such as cars) or has been used as a location for bonfires for example, this will have an extremely large impact on the efficacy of Magnetometry in that area and will mask any archaeological anomalies. In that instance, it may be that another technique could be employed. However, this of course depends on the site in question and we are always happy to discuss the possibilities.

What are you trying to find?

Last, but certainly not least, it is always useful to know what, if any, archaeological remains are expected. The size and type of archaeological remains being prospected for, especially for research, will influence the  instrumentation and sample intervals deployed. This is not only time-effective but cost-effective as it means the survey will detect the items of interest.

Having a full suite of geophysical techniques means that we can find most types of archaeology, however, some techniques will fair better at finding certain types of material whereas others will be inapplicable. In the case of stone and masonry remains (such as, for example, a castle) a magnetometer will not be able to detect the stone material of the structure. In this instance, where there is a known stone-built monument or structure we would probably advise Earth Resistance or perhaps an Electromagnetic Induction Survey for your particular needs.

Processed data and interpreted image of a stone-built leper hospital found in an Electromagnetic data set (white represents stone/high resistivity)

Another consideration when specifying a technique appropriate to the type of archaeology being sought is the size and morphology of the archaeological elements being investigated. Narrow slot trenches, pits, post holes, grave cuts, relict flowerbeds or other small dug features will be extremely difficult to find using standard sample intervals. Very high resolution surveys can be used to locate small elements, however in the case of very small features such as stake holes, neonatal burials or small pits the archaeology is so ephemeral that even a very high resolution survey may not locate any remains. All of these things are taken into consideration along with the terrain and type of geology and we will happily oblige in recommending the most effective technique or combination of techniques for the archaeology being investigated and in full consideration of the environment we are searching in.

If there is anything else that you are curious about in regards to what we can do for you, then please feel free to contact us.