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)
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!
Funding: The Heritage Council – Adopt A Monument Scheme
In October of this year, Earthsound had the chance to carry out one of the most spectacular surveys the company had ever tendered for! From the 2nd to the 6th, our full complement of field crew (Heather, Cian, Ursula and Ciarán) were out in the wilds of southwest Donegal. The subject of the survey was a cashel, on an island, in a lake!
Doon Fort is a stunning stone stronghold, covering most of a small island found in Doon Lough. The massive dry-stone fortifications rise to a maximum height of c. 5m at the entrance and range in thickness from 3m to 4m. The cashel contains not only a crawl space, but also a passageway with stairs within the wall itself, which lead up to the wall walk.
Approached from the east, launching from the lakeshore slipway, the fort makes an impressive appearance as you row up the lake and round a headland. Loading up a small row boat and a canoe, the Earthsound crew made the journey up and down the lake with all the equipment needed to carry out the survey each day.
A comprehensive survey was undertaken of the cashel. The interior was investigated with high resolution surveys using a single gradiometer, a hand-held electromagnetic instrument and a twin-probe earth resistance meter. In addition to these, a topographic survey was also conducted. An additional aim of the survey was to produce a 3-D model of the monument. Photographs documenting the structure were taken from all positions: inside the fort, on top of the wall and outside the fort from a canoe and adjacent islands.
Despite the small scale of the survey, a week was set aside to complete it. This was due to the changeable and harsh weather conditions sometimes encountered in this part of the country. As it happened, both the Monday afternoon and all of Wednesday were written off due to high winds and stormy conditions. On the other hand, the Tuesday, Thursday and Friday were very successful days, with all work being carried out in good conditions and an amazing setting!
Doon Fort is looked after by the Ardara GAP Heritage & History Group who are working very closely with the landowners, the McHugh family, and, in the weeks leading up to the survey, their members and many local volunteers worked to clear the interior of heavy vegetation and the dense ivy from the walls. Without their hard work and dedication, the survey would not have been possible. The survey was commissioned by the heritage group as part of the ‘Adopt a Monument’ Scheme being administered by the Heritage Council (https://www.facebook.com/AdoptaMonumentIreland/) and Abarta Heritage (https://www.facebook.com/AbartaHeritage/).
Unfortunately, there is restricted access to the monument. It is vital that anyone trying to visit the site, that they contact the landowner prior to any visit. Please see Ardara GAP Heritage and History Group on Facebook (https://www.facebook.com/ardaraheritage/) for more info.
At the start of November Earthsound headed down to the village of Kilfinnane in Limerick. This quiet village hosts one of the most impressive monuments to be seen in the Irish landscape – a lofty motte, rising to 12m in height, surrounded by a series of imposing banks and ditches.
Standing atop the motte, sweeping views are given of the surrounding landscape – taking in Keale Mountain to the south, the Ballyhoura Hills to the southwest, the Galtee Mountains to the east, and a rolling countryside to the north.
View looking south from on top of the monument – Galtee Mountains on the left, Keale Mountain on the right and Ursula with the EM cart (Photo: C. Hogan)
This monument has been adopted by a community council and Tommy O’Sullivan acted as liaison for us. He, along with other enthusiastic locals, were able to fill us in with a great amount of detail of ‘The Moats’ recent background and older history.
Little is known about the history of the monument and there are very few other monuments recorded in its immediate vicinity. A standing stone is located in an adjacent field. The Kilfinnane Community Council has made great efforts to assemble of huge range of historical documents, local knowledge and folklore to create a greater understanding of the landscape – and the geophysical survey is another step towards this.
A broad survey was undertaken of the lands surrounding the motte. The site was investigated using an eight-probe magnetometry system and an electromagnetic instrument. The aim of the survey was to identify any associated anomalies, perhaps a bailey, or other unknown anomalies. The magnetometry covered the entirety of the survey area, whereas the EM was used to target the area adjacent to the banks and topographic features elsewhere.
Ursula surveying with the EM cart in front of the motte (Photo: C. Hogan)
Acknowledgements to the landowner Tom for allowing us access to his lands for the survey.
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.
On top of the hill with the Earthwalker Magnetometer Array
Survey of Knocknashee hillfort interior using Earthsound’s Earthwalker Magnetometer Array
Cian & James, walking the earth, with the Earthwalker
Our latest magnetometer array is the Earthwalker – the first in-house piece of equipment created by Earthsound Geophysics. The Earthwalker was designed, sourced and built by Earthsound’s Cian Hogan, with input and help from all staff.
Cian constructing the Earthwalker
Our regular multi-sensor magnetometer array uses a wheeled cart – however, due to increasing demand to undertake fieldwork in remote and challenging terrain, a more suitable and sturdy option was required. From uplands and rocky outcrops to dunefields and the inter-tidal zone, Earthsound’s new Earthwalker array allows us to carry out high-resolution GPS-acquired magnetometry no matter what the terrain.
The Earthwalker had its maiden survey at Knocknashee Hillfort, as part of the 2017 season of the Knocknashee Archaeology Project – and it was a great success! It took 8 people to transport our survey gear – 2 x GPS, 8 x ranging rods, food for the day (most important!), a metal detector, survey flags, 4 x magnetometers, an electronics box, and the Earthwalker array – to the top of the hill.
Heading up Knocknashee with the Earthwalker
Earthsound surveyors worked together to collect data over 9 Ha of data, developing a methodology and refining the array.The Earthwalker delivered the first large scale, high-resolution assessment of the Knocknashee hillfort interior.
Project: Vinegar Hill Battlefield Research Project
Location: Vinegar Hill, Enniscorthy, Co. Wexford
Client: 1798 Interpretation Centre
Funding: Wexford County Council (2016, 2017)
Aim: Earthsound, together with Rubicon Heritage Services, IT Sligo and Cotswold Archaeology have carried out a series of geophysical and metal detecting surveys across the purported location of the 1798 Vinegar Hill Battlefield, with a view to confirming its location and systematically investigating elements of the battlefield. Earthsound have carried out high resolution Magnetometer, Earth Resistance, Electrical Resistivity Tomography and Metal Detection surveys.
Outcomes: The geophysical survey results are currently being written up for publication in a monograph and the investigation will be the subject of an upcoming documentary.
Client: Dr. Dirk Brandherm, Queen’s University Belfast
Funding: Royal Irish Academy Grant (2016, 2017)
Aim: The purpose of the geophysical surveys was to assess hut sites on the plateau of Knocknashee, a hillfort complex which also contains two Passage Tombs. In 2016 the entire hillfort interior – more than 20 ha in size – was assessed with Magnetic Susceptibility to identify zonations of activity. Specific clusters of huts and enclosures were further investigated with high resolution Magnetometry and Earth Resistance surveys. The 2017 survey used the ‘Earthwalker’ Magnetometer array across the southern half of the plateau and targeted Metal Detection surveys.
Outcomes: The 2016 geophysical survey results are currently being written up for publication in a future edition of Emania. The results were used to target a series of excavations in 2017, under the direction of Dr. Dirk Brandherm.
Community Engagement: We’ve given a number of lectures on our work in Athy at the Athy Heritage Centre Museum, we’ve been visited by local schools and filmed for a short video that documented the surveys for the benefit of the local national school.
Outcomes: The 2013-2016 geophysical surveys have been used to aid the management of the Athy Town Walls and castles in a rapidly developing urban area. For more information on our work at Athy, see our collection of Blogs from Athy.
Magnetometry and a great view of Dublin City from Mountpelier Hill. Image: Abarta Heritage
Project: The Hellfire Archaeology Project
Location: The Hellfire Club, Mountpelier Hill, Co. Dublin
Client: The Hellfire Club Archaeology Project, on behalf of Abarta Heritage and South Dublin County Council
Aim: The purpose of the survey was to assess two Neolithic Passage Tombs on top of Mountpelier Hill and the land surrounding the 18th Century Hellfire Club. The site was investigated with high resolution Magnetometer, Electromagnetic Induction and Earth Resistance Surveys, as well as LiDAR.
Community Engagement: 3 volunteers worked with Earthsound geophysicists over 3 days (volunteer labour contribution: €986)
Outcomes: The 2014 geophysical survey results were used to target a series of excavations in 2015 by the Hellfire Club Archaeology Project.
Hellfire Club, Co. Dublin
Dr James Bonsall is assisted by the volunteers carrying out an Earth Resistance Survey over a Neolithic Passage Tomb. Image: Abarta Heritage
Earth Resistance Survey at the Hellfire Club and Passage Tomb
EMI Survey over the Passage Tomb
EMI Survey beneath a UAV photography survey
EMI Survey overlooking south Dublin
The geophysical survey was carried out as part of The Hellfire Archaeological Project in conjunction with Abarta Heritage. The site is located on top of Montpellier Hill in the Dublin Mountains which affords it a panoramic view of Dublin City and Bay. The summit of Monpellier Hill contains the remains of a hunting lodge built by the politician William Connolly in 1725. Adjacent to this is the probable remains of a prehistoric monument and it is thought that the lodge itself may have been constructed of stone robbed from these monuments.
According to folklore the roof had been blown down by a phantom from one of the tombs and Connolly had the roof reconstructed in stone. Subsequent to Connolly’s death, the lodge lay in disuse for up to 10 years when it was leased by his widow Katherine to the Earl of Rosse, Richard Parsons. Parsons was a well known socialite and one of the ‘Young Bucks of Dublin’, a group of aristocrats who allegedly engaged in debauchery and possible Devil-worship, essentially what was to become the Hellfire Club. There are no direct accounts of Hellfire Club meetings occurring at Connolly’s Lodge on Montpellier Hill, however it is highly likely owing to its isolated location and association with Parsons.