Geophys 101: Magnetometry

Southampton team member undertaking magnetometry survey of Kingston Maurward in Dorset. Photo courtesy of Kristian Stutt.

The last cool bit of kit our friends at Southampton are bringing to help us with our geophysical survey is called a fluxgate gradiometer. This tool is under the broader heading of “magnetometry,” where scientists have studied the behavior of magnets and magnetic fields. Unlike the two previous survey methods we discussed, this is a passive system: we are not sending out signals and recording their manipulation; we are monitoring changes in natural forces. There are many different versions of magnetometers that allow scientists to find specific information like the intensity of a magnetic field or sets of correlated readings like intensity coupled with direction. The earliest magnetometer is the magnetic compass: it only tells you one thing, which is the direction of the earth’s magnetic field, but one can use that to find North. When the lowly compass was placed near an electric current, voila, electricity and magnetism were finally proven to be besties. The unification of these two branches of physics is the study of electromagnetism!

A gradiometer in particular measures the rate of change of a quantity, so for us it will find the rate of change (“gradient” if you remember calculus) vertically in the magnetic field of the immediate area by comparing readings from 2 or more sensors stacked on top of each other. If you can track these variations, you can detect certain types of features, but usually no more than 2 metres down. Filled-in cut features (ditches and pits), hearths and burnt material, and ferrous (iron-y) objects are the subsurface anomalies a fluxgate gradiometer can find. These features can produce small but measurable variations in the magnetic field produced by the Earth. The “fluxgate” part of the name refers to the movement in the coils and core of the system, which have a strange technological history with respect to space exploration. A fluxgate magnetometer in essence measures two things: intensity and direction of the magnetic field.

There are different versions of the fluxgate gradiometer which have their own pros and cons: one probe can be carried through wooded areas, while the multi-probe carts are much faster gathering data but limited to open ground. In general, this method works best in areas without a lot of background noise like buried ferrous objects or igneous (volcanic) bedrock. Also, much like Anakin Skywalker, magnetometers hate sand.

The first non-compass magnetometer was invented in 1833 by Carl Friedrich Gauss, a German math nerd who did a lot of cool things. It was surprisingly simple, involving bar magnets reacting to the Earth’s magnetic field and each other. Around the same time and thereafter, other European scientists of many adjacent fields of study were observing, hypothesising, and experimenting with magnetism on a large scale. They were collaborating to try to unlock the mysteries of Earth’s magnetic field: this was the “Magnetic Crusade.” Observatories were built, expeditions to the poles and equator were launched. The amount of data collected by hand, first through direct observation and then through photography of instruments, was absolutely massive. The practical reasons for this investigative trend were mostly to make navigation, especially for military purposes, more accurate and safer, but, as with most scientific pursuits, geeks like us also just like to know things, to truly understand things, about this planet we all share.

It wasn’t until over a century after Gauss’ magnetometer that the fluxgate mechanism (see the “coils and core” link above in the second paragraph) was invented. Hans Aschenbrenner and Georg Goubau published their design in 1936, but it seems to not be online in translation from the German; their paper does pop up in citation by a lot of fluxgate literature still This timing during the interwar period and Germany’s rearmament proves to be pivotal for development of the tech. Five years later, Victor Vacquier successfully made a mobile fluxgate magnetometer while based at an oil firm in the US; the US Navy had been looking for just such a technology for recon over the ocean so they popped them on planes one year after that (end of 1942). Time to hunt some submarines! (Keep reading that last link to learn how this usage revolutionised plate tectonics theory.) Fluxgate magnetometers were first employed in archaeological study in the 1950s, so so far they have been used on the surface of the Earth, under the ocean at the spreading zones of the seafloor, and even in space!

Here on the surface of the Earth, we have the results of our last geophysical survey. Dr. Groves describes the three different types of anomalies after the data gathered in 2006 was processed. Magnetic anomalies can be positive, negative, or dipolar (mixed), and there are several ways material gets magnetised enough to make a detectable deviation from surrounding material. Positive anomalies may represent ditches and pits (and certain types of geology), because topsoil is really susceptible to magnetization and that is usually the backfill of such features.

Negative anomalies might be stone foundations or geological variation including non-ferrous and non-magnetic rocks, but unfortunately sometimes they also turn out to be pits with a mixture of backfills, negating the magnetic signature relative to the surrounding material because the filling soil isn’t all the same thing.

Here’s a really nice example of a Neolithic enclosure in Riekofen, Germany provided in the magnetometry entry in the Encyclopedia of Geoarchaeology. The two inner ditches are positive (black) anomalies, which is expected because they were filled in with magnetised topsoil. The outer two ditches are light grey, closer to the white of a negative anomaly, because they were saturated with water and the ferrous particles dissolved and thus were not detected in quantity relative to the surrounding ground.

Riekofen Neolithic enclosure in Bavaria, Germany. The postive (black) and negative (light grey) anomalies represent ditches in-filled with differently magnetised soil. (Fassbinder, p. 507)

The third signature we find in our survey are the dipolar anomalies often are associated with burning (accidental or purposeful like in hearths and kilns) or ferrous material. Figure 3 of the Groves report includes linear dipolar anomalies along the fence line, which is common, and lots of smaller dipolar anomalies in the area left unexcavated. Could this be modern ferrous rubbish just under the surface? Or are they iron objects like knife blades and fittings used as grave goods in as-yet undiscovered burials? Unfortunately, these smaller anomalies don’t seem to line up with cut features like the pits or graves that show up when we compare the results to our resistivity survey. They remain a mystery.

Works Cited/Further Reading:

Cawood, J. (1979). The Magnetic Crusade: Science and Politics in Early Victorian Britain. Isis, 70(4), 493–518. https://www.jstor.org/stable/230719 (paywalled)

Fassbinder, J.W.E. (2017). Magnetometry for Archaeology. In: Gilbert, A.S. (eds) Encyclopedia of Geoarchaeology, 499-514. https://www.researchgate.net/publication/309386014_Magnetometry_for_Archaeology

Goodman, M. (2019) Follow the data: administering science at Edward Sabine’s magnetic department, Woolwich, 1841–57. Notes and Records of the Royal Society Journal of the History of Science, 73, 187–202. https://royalsocietypublishing.org/doi/epdf/10.1098/rsnr.2018.0036

There’s a neat classroom handout from the US National Parks Service here that explains how magnetometry has been used to explore Indigenous village sites in North Dakota.

This blog is brought to you as part of our 2023 grant-funded activities through the generosity of the Castle Studies Trust.

Geophys 101: Electrical Resistivity

Southampton team members undertaking electrical resistivity survey of Kingston Maurward in Dorset. Photo courtesy of Kristian Stutt.

Electrical resistivity is another survey method we will employ this season in Week 3!

When you were in primary school science (and if you were really clever, secondary school physics), you probably encountered several lessons on electricity. You may not have gotten as much firsthand experience out of the formal classroom lessons, say, as someone who licked a battery or stuck something in an outlet, but then again we all have our learning styles. (DO NOT DO EITHER OF THOSE THINGS. WE’RE SERIOUS.)

Electricity is clearly a Big Deal in modern society, as we rely on it for everything from light bulbs in our flats to the smartphones in our hands. Electricity is also part of the human body, conducted by our cells (through a little bit of chemistry involving ions), telling us about stimuli, reacting to stimuli, and making our hearts pump. But in every circumstance, it all comes down to subatomic particles: protons in the nucleus of an atom are described as positive (+), while electrons that encircle the nucleus are described as negative (-). Electrons can get moving between adjacent atoms of conductors like copper, and zap! You’ve got an electrical current. We’ll get back to this in a mo, just keep that image of flowing electrons in your heads.

The equipment we are going to be using has two metal electrodes 50cm apart that you stab (gently) into the earth at predetermined, regular intervals along a measured axis. Most of our team has done this insert-take readings-repeat process along a surveyor’s tape-anchored grid system, recording a reading or two every metre across fields, animal paddocks, and the occasional golf course so far in our careers, but not yet at Bamburgh! Once you’ve done one whole length of the survey area, you do the same distance again, this time just sliiiiiightly (a metre) to the left or right. Eventually you will cross the length and width of the survey area multiple times without tracing over your previous footsteps. This builds up a picture of the subsurface one grid square, and then strip, at a time. (There’s another pair of probes outside of the survey area which we will talk about further when we actually see the full setup of the equipment that the Soton team is bringing; unhelpfully, a “twin probe array” like the one we are expecting actually has 4 prongs in the full system: the mobile pair and the stationary pair.)

Wait, wait, wait…but what are the machine and the various electrodes actually doing? The rig is sending an electrical current through the soil between the prongs. Conductivity means the current flows relatively easily; resistance is therefore the opposite of conductivity. How conductive the earth or buried features may be is heavily reliant on moisture content and the arrangement of pores within the medium the current is meant to pass through. If the current passes through with little resistance, features like pits and ditches that have been filled back in with material may lie under the surface. Areas of high resistance may represent buried foundations, trackways, or rubble.

This system is adaptable to a degree: you can configure it to work at varying depths by changing that initial spacing of the mobile probe pair, but this also changes the resolution of the data we are gathering. Even though we are conducting currents, the readings are not going to be skewed by metal artefacts below the surface. This is however a slower method of survey than GPR because you must stop and prod regularly rather than walk comfortably rolling an array along each row. Also, it’s not ideal in winter surveys because of the amount of prodding into frozen soils.

It is surprisingly difficult to get hands on the output of resistivity surveys from other sites to share as examples, so for now take a look at our last resistivity survey here. Figure 4 shows you the output from the processed data. It takes a lot of training to be able to read and interpret these surveys, so please don’t be put off by that initial black and white image. Figure 5 shows you the interpretation by Dr. Groves and their team. The small high resistance areas (light blue) could be stone-lined graves, while the small low resistance areas (light green) could also be graves, but only filled with soil. The other larger blue anomalies seems to be dune-related, while the large linear green anomaly could be a soil-filled ditch.

Nota Bene (yes, we did get a little Latin up in here, simply meaning “note well”): We often point to 18^th-century American mega-flirt Ben Franklin as the first mainstream electrical experimenter, but knowledge of electrical phenomena such as shocks from electric eels (weirdly enough, not truly eels but closer to catfish) and static generated using amber can be found in sources as far back as the Egyptians in the Bronze Age for the former, and Archaic Greece for the latter. Franklin was studying lightning when he confirmed it was a type of electrical discharge, but he was building his experiments on the work of scientists from the century prior; one such scientist was William Gilbert who wrote extensively on magnetism, but disbelieved its connection to what we call electricity. Gilbert was not only physician and philosopher to the stars (Elizabeth I), but also the first scientist to posit that we ourselves are living on a giant magnet. More on that when we get to magnetometry! We now know that these two forces are united through electromagnetism: an electrical current generates a magnetic field, creating a basic force of nature that affects things as small as individual atoms to as large as our whole planet.

This blog is brought to you as part of our 2023 grant-funded activities through the generosity of the Castle Studies Trust.

Geophys 101: GPR (Part 2)

Historic England GPR survey at Stonehenge. (Photo by Historic England Geophysics Team.)

Okay, okay, so now you are all experts on radar, and we can get to the ground-penetrating bit. If you missed part 1, catch up here.

Funnily enough, patents for using electromagnetic waves to find subsurface features were filed shortly after the original Hülsmeyer patent for his Telemobiloscope in 1904. You can view a digitised image if you go here and click “Original document,” and the European Patent Office does offer a machine-translation of the description into English if you would like to get the gist of the original text.

In 1910, Drs. Leimbach and Löwy in Göttingen patented a technique that required antenna to be lowered down boreholes: German original; English translation.

The second is issued in 1926 by Dr. Hülsenbeck and his team based in Frankfurt that uses what is translated as “electric shock waves” and rely especially on conductivity differences that suggest a change of material: German original; English translation. Conductivity in particular will become key to the next survey technique we will discuss.

Briefly in the interwar period, radio waves were experimentally used to measure glacial thickness, but did not really take off until the 1960s and 1970s. NASA’s plans for lunar exploration were becoming a reality, eventually performing their first official GPR experiment 5 years later while Apollo 17 was in lunar orbit. (Conyers, p.68)

So folks had already shot radio waves into glaciers and the moon, but only turned to archaeological applications in the mid-1970s, with early projects at the Ancestral Pueblo site of Chaco Canyon, NM, USA. (Conyers, p. 68) Use of GPR in archaeology steadily increased, and when computing tech became more robust, it became possible to handle larger datasets that provided clearer visualizations. (Conyers, p. 68).

The GPR systems we use today send radio waves in pulses vertically into the ground as you move the rig across the ground surface. The signal is reflected back to the instrument, and both the time it takes for and the strength of the return signal are recorded. Factors like the material below ground (stone, sand, clay), compaction (who packed the material is), and water retention of the different materials all affect the return signal. GPR works really well on sites with sandy soil, and it is often employed to search for masonry and ditches; this is perfect for us because our target area is to trace the medieval ditch at the outworks.

We can then build up a vertical profile, a cross-section of the subsurface to a known depth, that is a side-view similar to our section drawings of stratigraphy (like a layer cake) of a trench wall. Look at the image below. On the vertical axis, you can see intervals of depth in centimetres; on the horizontal axis, you can see the distance in metres from the edge of the survey area. Interpreting these profiles takes experience! The main anomalies are all first appearing at roughly the same depth, but one is giving stronger disrupted signal than the others, which is why the archaeologist (Conyers) believes he is detecting coffins made of different materials. When Conyers published this article, GPR had not been extensively used on graveyards; in recent years, however, it has been employed at sites of former residential schools (mandated schools for Indigenous youth in the US and Canada) to search for lost burial grounds.

GPR profile showing different coffin signatures in an early 20thC cemetery (Conyers’ Figure 3 on page 67).

If you can compile enough of these profiles, you can also create a survey in plan (overhead view) at different depths, but this time by slicing horizontally through the collection of vertical slices. Think of a loaf of sliced bread: each slice is your vertical profile, but now imagine taking a bread knife (or machete) and cutting the loaf horizontally instead to get an overhead view. They are called “depth slices” or “time slices.” Check out the composites below showing what the overhead view looking down would be at different depths for a crypt at Calvary Cemetery in St. Paul, MN, USA.

Depth slices of a crypt at Calvary Cemetery in Minnesota published under a Creative Commons licence by Wikipedia user Tapatio (US based geophysicist active on geophys articles and discussions on Wikipedia in the last decade) in 2010.

If you are interested in profiles and their correlating depth slices for a UK site in 2020, check out the appendix of Gaffney’s team’s work on Neolithic features near Durrington Walls here. Full text linked below.

When we combine our vertical profiles with our plan-view depth slices, we can also build a 3D model of what is under the ground surface. We hope to use the various plans and datasets to be compiled from our surveys and excavations to create contemporary models and period or phased reconstructions of Bamburgh’s features in the future.

Works Cited:

Conyers, L.B. (2006). Ground-penetrating radar techniques to discover and map historic graves. Historical Archaeology, 40(3), 64-73. https://www.jstor.org/stable/25617373 (paywalled)

Gaffney, V. et al. 2020 A Massive, Late Neolithic pit structure associated with Durrington Walls Henge, Internet Archaeology 55. https://intarch.ac.uk/journal/issue55/4/full-text.html

This blog is brought to you as part of our 2023 grant-funded activities through the generosity of the Castle Studies Trust.

Geophys 101: GPR (Part 1)

Southampton team member undertaking GPR survey of Kingston Maurward in Dorset. Photo courtesy of Kristian Stutt.

The first geophysical survey technique we are going to employ under the guidance of our guest specialist is ground penetrating radar (GPR).  Radar stands for “radio detection and ranging” though it originally was all-capitalised as the acronym RADAR. Ranging is the term for measuring distance by timing how long between when a signal is sent out from a location and received back, an “echo.” Scientists and engineers have developed other technologies that have “ranging” abbreviated in their names, such as SONAR (an earlier technology but renamed to be analogous to RADAR but using sound navigation) and LiDAR (aerial survey using a laser as “light detection”). All three of these ranging methods have been applied to archaeological sites in the past few decades!

At its most basic level, a transmitter sends out electromagnetic waves (radio or microwaves) from an antenna that then are reflected or scattered. Giant metal aircraft are especially good at this part. A receiver (which can be the same as the antenna emitting the waves) collects the reflected signal, then the data on return signal strength and timing can be processed to be interpreted. Properly interpreted modern radar data can tell you how far a target is (range), how high in altitude (angle), what direction it’s travelling (bearing), speed, and how many targets there are. Some sophisticated systems can even differentiate between bird species!

The roots of radar stretch back to at least the latter half of the 19^th century. A Scottish physicist, James Clerk Maxwell, had theorised mightily on electromagnetism, understanding that a spectrum of radiation existed and predicting the existence of radio waves on that spectrum. He worked in multiple fields of science, and his contributions were game-changing; you can listen and learn about some of them here. Two German scientists took the next steps with their experiments based on Maxwell’s theories: Heinrich Hertz (yes, THAT Hertz, here and here) realised that different electromagnetic waves could pass through some materials and be reflected by others like metal objects; Christian Hülsmeyer applied this to ships (an idea also posited by Mr. Radio himself, Guglielmo Marconi), and patented the first bit of tech that we could recognise as a precursor to radar early in 1904. During WWI, the only methods for detection of aircraft via soundwaves in use were designed specifically for acoustic signals the human ear could amplify and perceive, and then triangulate: the war tubas and sound mirrors.

Another Scot, Robert Watson-Watt, emerged in the post-war period as critical to the development of radar, drawing on his experience with related techniques for finding radio signals of lightning strikes and finding radio systems themselves (“radio direction finding”). Arnold Frederic Wilkins joined Watson-Watt’s team in 1931, working on the reflection of shortwave signals off of aircraft, and eventually their parallel strands of work were pursued under Henry Tizard’s Committee for the Scientific Survey of Air Defence. When war loomed again in the mid-1930s, the Air Ministry was looking for new technology to give them the upper hand should war break out: what they wanted was a death ray to match the intelligence rumours coming out of Germany, but what they got was a modest proposal for radio detection. But that was enough to set in motion the development of a true radar system in the UK.

Chain Home coverage map 1953, public domain.

By the onset of WWII, multiple countries had been experimenting with what we call radar, but our heroes above produced something completely new. A series of radar stations, called Chain Home, was the early warning system employed by the RAF that saved so many lives of air crew, ground crew, and civilians; it allowed the strategic scrambling of fighters when the RAF was under the most pressure from the Luftwaffe. The Battle of Britain was won in part due to the effective implementation of radar as a component of a larger air defence apparatus called the Dowding System. Chain Home and its adapted partner Chain Home Low (for low-flying craft) are now mostly absent from the landscape save for a recently listed CH mast in Essex and the occasional unassuming concrete bunker like this CHL station in Craster on the coast 13 miles south of Bamburgh.

CHAIN HOME LOW STATION: e25207 (Extant) M28 / K28 Craster.

The tall and short of it: (Left) Chain Home receiver towers at Woody Bay near St Lawrence, Isle of Wight, “Remote Reserve” station to Ventnor CH. Source: (CH 15174) IWM. (Right) Craster bunker for CHL, source linked above in text.

Since then, radar has become commonplace in military and meteorological pursuits. It had been designed to function in one medium, air, but when did someone decide to point those electromagnetic waves into the ground? Stay tuned for Part 2 tomorrow!

This blog is brought to you as part of our 2023 grant-funded activities through the generosity of the Castle Studies Trust.

Geophys 101: What and Why

Radar survey of the West Ward of Bamburgh Castle in 2002 before the opening of Trench 3.

As mentioned previously, we have been awarded a grant from the Castle Studies Trust to undertake various surveys of sites of interest in and around the outworks we’ve been excavating the past two summers. This summer, we will have a specialist from the University of Southampton join us to supervise three non-destructive and minimally-invasive methods of geophysical investigation: ground penetrating radar, electrical resistivity, and magnetometry. We have chosen techniques that we believe will help us identify the remains of the castle ditch and possible trackways to access the early medieval entrance of Saint Oswald’s gate. We will be sharing our methods and preliminary results here on the blog, temporarily moving away from our daily in-season format to provide longer-form posts pre-season before arriving on site to provide real-time news. Updates will still be frequent during the season, but we are also looking forward to the other methods of dissemination of our research that this funding will enable. You’ll see a notice like this on all posts related to the grant funding so you can follow along with our progress!

This blog is brought to you as part of our 2023 grant-funded activities through the generosity of the Castle Studies Trust.

What on Earth…

“Geophysics” is a field of science that focuses on the earth’s physical processes and characteristics. Geophysical surveys use various types of technology deployed on land to differentiate between soils, rocks, structures, and subsurface features in a target area. Many forms of geophysical survey are well-suited for large scale geological and mineral resource management, but in archaeological applications we tend to focus most on electrical and electromagnetic techniques. The choice of technique relies heavily on both the physical landscape and the research aims of the surveying team. We will cover our approaches mentioned above in forthcoming blog posts, but why should we be using these survey techniques at all? We’ve got trowels and mattocks, why can’t we just jump straight into the digging?

Geophysical surveys help us figure out where the best places to dig to try to solve our research questions. Without them, we would have to rely on extant features like ruins, barrows and mounds, or crop marks (differences in height and water retention of vegetation overlying buried stuff) to know that anything was there. That’s how a lot of antiquarians and early archaeologists found places to dig, but just as our methods of excavation and laboratory care have improved, our ways to search for possible sites have also become more efficient. Geophys, as it’s sometimes abbreviated, can be performed (with a bit of patience and sturdy boots) over massive areas to develop a picture of what’s underground before you ever even have a chance to strip the turf.

The immense amount of data we record using the various survey machines doesn’t get spit out as a sheet saying “Wow, you’ve got a Roman bathhouse under here!” Instead, we are given a computer-generated visual of the differences between the various materials underground. We can see the different densities or electrical conductivity (how well a current can move) or magnetic variation of the subsurface material to a specific depth, depending on our method and resolution (which itself is based on how many data points we record). If we had a structure, for example, we would probably have lines of building stone and the outlines of voids that had been filled in with slightly looser soil or rubble. This gives us a little preview of what to expect on the way down, and it allows us to make better-informed decisions on whether, where, and how to excavate.

Archaeological excavation is something you can only really do (properly) once! Sure, sometimes we re-excavate areas like Brian Hope-Taylor’s trench edges to cross-reference our data with the surviving stratigraphy from his section walls, but we can’t truly see the site the way his team did as they dug down, down, down. This is why archaeology has so much paperwork and huge image archives: we record every context on a context sheet (a form that has sections for soil description, dimensions, artefacts, and tentative interpretation), we plan all of the trench multiple times on our grid paper, and we photograph all the areas we’ve worked on throughout the season. But sometimes we decide not to excavate, and often that is because the features and possible artefacts underground are not at risk in the same way they might be if pulled out of their cosy little soil beds (as soon as you change the reasonably-stable environment of an artefact or ecofact, it almost always starts to degrade faster). Geophysical survey in some instances can prevent or at least delay the excavation, which in essence is a type of regimented, meticulously-recorded destruction of the primary source that is a site. We will likely develop new methods of survey that provide even clearer data to interpret before moving a single shovel of soil, just as we will likely invent new techniques to gather evidence from the buried features and surrounding earth during excavation. By choosing not to excavate right now, we can give future archaeologists a proving ground for data collection methods we haven’t even dreamed of.

To read an open-access report of the geophysical surveys of the Bowl Hole (early medieval, 7^th-8^th century) cemetery, click here. Our friends at Durham employed magnetometry and electrical resistivity, undertaking their surveys in December 2006.

Funding Success for the Bamburgh Research Project with the Castle Studies Trust

The Bamburgh Research Project (BRP) are pleased to announce that we have been successful in securing £9306 from the Castle Studies Trust (CST).

Over the next 12 months the BRP will be utilising the funding to further explore Bamburgh Castle’s medieval outworks, particularly the area outside St Oswald’s Gate where our current excavation is underway as part of our annual field school. Our project is titled ‘Contextualising Bamburgh Castle: wells, towers, mounds and more!’

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St Oswald’s Gate and the Medieval Outworks

St Oswald’s Gate and the outworks beyond lie in the area of the original entrance to the castle. It is very likely that the siege castle (named Mal Voisin in the Anglo-Saxon Chronicle) was built close to this gate in AD 1095. When the main access was re-sited, the entrance here remained as an important postern. Perhaps serving a small adjacent harbour immediately to the north of the site. This area now forms the BRP’s main investigative focus. The outworks consist of strong walls enclosing a trapezoidal area with the Tower of Elmund’s Well. With a more recent wall and postern to the west.

The outworks at St Oswald’s Gate are a rare case at Bamburgh as they have not been subject to extensive rebuilding in the post medieval period. Other than the reconstruction of the tower as a cottage, the outworks represent an astonishing window into mostly unaltered medieval fabric still standing at Bamburgh.

Foreground shows the area currently under excavation by the BRP with St Oswald’s Gate visible at the top of the steps and West Ward of Bamburgh Castle present in the background.

Work to Date

Recent investigation by the BRP has revealed that a substantial structure still survives below ground. This is in the form of an L-shaped corridor and steps down into the room that is thought to be the tower basement that contained the well. The presence of two splayed narrow windows appears to further indicate that this is part of the medieval Elmund’s Tower. The 2023 excavation season aims to reveal the full extent of the tower and identify any remains of the well depicted on the 19th century survey. You can find out more about our ongoing excavations in this area by taking a look at earlier blog posts: Investigations beyond St Oswald’s Gate: End of Season Overview.

What will the CST Funding be used for?

There are two primary aims for the CST funding. The first is to contextualise our recent excavations at Elmund’s Tower through geophysical survey (GPR and Magnetometry) and undertake a preliminary masonry survey of the castle’s associated extant outworks.

The geophysical survey will provide context to the area immediately outside of the outworks and identify if the castle ditch (seen as a rock cut feature at the Great Gate) extends all the way along the front of the castle. As part of the masonry survey the project will be using photogrammetry to create a 3D model of the standing outworks and internal structures of Elmund’s Tower. The survey will be undertaken in conjunction with a metric survey of the structures outlines so that a photo-real, stone by stone, 3D photo model can be used as a management tool for future plans, including consolidation work.

The investigation of the area will be used to aid in making management decisions to ensure the preservation of the outworks. More broadly, the proposed investigations will assist the interpretation of the extensive, but more complex and disturbed stratigraphical sequences recovered elsewhere in the castle, principally the West Ward.

We will also be using the photogrammetry and geophysical surveys as an opportunity to upskill BRP staff and provide add-on benefits to students during our annual field school (July 2023).

The second focus for the funding will be on disseminating our discoveries to the wider public. Bamburgh Castle is in the process of re-focussing the story it tells the public, giving greater focus to its medieval and early medieval history through a new website, signage throughout the grounds and new displays within the castle itself. However, the medieval outworks are inaccessible to the public and there is currently no opportunity to highlight the ongoing research into this area of the castle and how the site was shaped by the surrounding topography. The funding will allow us to create and install signage for visitors with a QR code for the 3D model, granting online access to Elmund’s Tower and the wider outworks. This information will also be replicated and enhanced with the creation of a new webpage on the Bamburgh Castle website. Alongside these permanent additions we will continue to share our work through our blog and social media.

Listen to two of our Directors discuss the project with the CST

Project Directors, Jo Kirton and Graeme Young, recently spoke to the CST about the project, which you can listen to here:

Make sure you follow our blog and social media accounts to see how the project progresses over the summer. We cannot wait to share what we discover!

Two places are now available to book in Week Three

Booking has filled up very fast this year but two places have now become available! These are both for Week Three (16th July to 22nd July) and as this is the week we will also be doing geophgysics as well as completing the excavation, it should be a really good one to be on.

Booking information, the booking form and email to ask any questions is available through this link

We look forward to seeing you in July

Archaeology of the Last Kingdom online talk

The Bamburgh Research Project will be taking part in an online talk to discuss the archaeology of the Last Kingdom.

Coinciding with the release of The Last Kingdom: Seven Kings Must Die, this event is designed to appeal to fans of the series, highlighting the ‘real’ history and archaeology behind the show.

The event is free for anyone to attend, and a recording will be made available on YouTube at a later date.

Booking and informaion for the online event can be found here: digventures.com/product/the-archaeology-of-the-last-kingdom

Introducing our Newest Director….

We are really pleased to introduce our newest Director, Constance Durgeat!!!

Many of you will know Constance as she has been with the project since 2010 and many more will recognise her from our social media and blogs. Constance has been an amazing team member and over the past few years she has managed our excavations at the castle and looked after everyone off site.

Constance first joined the Bamburgh Research Project as an undergrad student in Art History and Archaeology from the Sorbonne University in Paris. After a Masters’ in Urban Archaeology, she moved to York to complete a Masters on Bamburgh’s metalworking area in Trench 3. She was then made supervisor of Trench One and carried out more roles over the years.

For Constance, coming from France where community archaeology does not really exist, it was (and still is) very exciting to get to teach anyone, no matter their level or education! Thanks to this interest, she has worked for seven years with the University of York, teaching first-year students fieldwork techniques and environmental processing. She has worked with multiple commercial companies, digging a variety of sites across England to keep her skills up to date. She now works as a Senior Archaeology Consultant with Rocket Heritage and Archaeology. Her main interests are Anglo-Saxon and medieval archaeology and buildings archaeology.…and travelling around the world when she has time!

Bamburgh and the Last Kingdom what’s the real story? Part 2 – An origin story

The Last Kingdom has proved incredibly popular, so we thought it was about time we explore how the story holds up against the archaeological and historical evidence.

You can read part one of this exploration here: Bamburgh and the Last Kingdom what’s the real story? Part 1- a real Uhtred??

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Where did this family come from?

The story of Uhtred from the books begins along with the Viking Age and with Uhtred as a boy at the time of the Viking Great Army. It then moves quickly on to the time of Alfred the Great. We have seen from the first blog that there was a real Uhtred whose life inspired the story but that he was from a much later time (the end of the 10^th and early 11^th centuries). In this blog we will look at the beginning of the books and see if we can find connections with the Bamburgh Family from this earlier time in the real history of the period.

The north after the creation of a Viking kingdom in Yourkshire (wikicommons)

The first Viking Age ushered in a period of great change across the British Isles, overturning once settled political structures. It began with a long period of raiding extending over more than two generations and then in the mid 9^th century the character of these attacks changed when large raiding forces were confident enough stay and over winter. Intentionally, or just as a consequence of their long term presence, these forces now became part of the power politics of the age and led ultimately to substantial settlement and the creation of Viking dominated kingdoms. This process began with the arrival of what the chroniclers called the ‘Great Heathen Army’ in the kingdom of East Anglia in AD 865. The sudden arrival of this force provided a very different challenge to the kind that the Middle Saxon kingdoms were uses to, and this quickly resulted in a degree of collapse of some of the power structures of the day. East Anglia was taken off guard and gave treasure and horses to the army, almost certainly hoping that they would leave, a policy that did work for a time.

It proved to be a particularly bad idea for the Northumbrians where two kings had been contesting the throne, meaning that there were divided loyalties to be exploited. The great army made there way north and attacked, seizing hold of the great city of York. The king of Northumbria on the throne at that time was called Aella having recently displaced a king called Osberht. One source suggests they were bothers but this is perhaps unlikely as others state that Aella was something of a usurper from an obscure royal line.

York was a hugely important city for Northumbria, being the seat of the archbishop and increasingly a major trading centre. The presence of wealthy merchants, and likely also a royal centre that had been stocked up with food for the next royal visit, would have been a tempting target. The Great Army seem to have intended to overwinter there as it was a well supplied site with a defensive perimeter. This situation was seen by the Northumbrians as so dire that both rival kings put there differences aside in order to fight to retake the city in the midst of winter. They attacked in the New Year of 867. The battle seems to have gone well for the Northumbrians at first, as they successfully broke into the city, but were unable to take advantage of this and it ended in disaster. The chronicle describes how those that had made it into the city were cut off before being killed or captured, leading to the collapse of the Northumbrian force with those that could making their escape fleeing. Of the two rival kings, Osbert was killed in the battle and Aella was reported as taken captive and then later put to death. Lurid tales from later legend describe his death as a human sacrifice. It is not at all certain that this was true, and many modern scholars seem to be sceptical, but we do have accounts from Arab sources of sacrifice of slaves being conducted by Vikings, so its by no means impossible.

A Thor’s Hammer pendent, of the few apparently Viking Age cultural items found at Bamburgh

In the aftermath of the battle the Viking army placed a puppet ruler called Ecgberht on the throne of Northumbria, to do their bidding in their absence. They then went south to raid other kingdoms. This worked for some five years before the Northumbrians rebelled, forcing the Viking army to return. In the end Northumbria was split along the lines of the old kingdoms that had, centuries before, come together to form it. Large tracts of the lands south of the Tees were divided up by the Viking force who settled and farmed the land. In the north, a rump of the kingdom north of the River Tees maintained its old kings for a while longer.

What was Bamburgh’s role in these turbulent times?

In the Last Kingdom books Uhtred is born into a family that are the hereditary rulers of the palace fortress of the kings of Northumbria. In history we know that it was from Bamburgh that the early kings of Bernicia ruled, from the middle of the sixth century, and that it remained one of the foremost centres until after the Norman Conquest. So there is no doubt that Bamburgh was and remained an important place throughout these times. We are told something of the arrangements by which important royal sites like Bamburgh were administered from annals and writings of the period.

In the absence of the royal court a palace like Bamburgh would have been administered by an important official called a reeve. It is almost certain that such figures were appointed by the king, but we cannot be certain that some roles did not become somewhat hereditary over time. It is frustrating that we have so few documents and references detailing how the governmental system of the Northumbrian Kingdom was administered, and not much more regarding the Northumbrian aristocracy- the warrior class from which such officials would have been drawn.

The records, as far as we have them, do let us piece together something of the aristocracy and offices that existed within the Northumbrian kingdom. Leaving aside the senior churchmen and Archbishop of York and thinking of the secular administration, the highest of these officials appears to have been the Patrician (in Bede’s Latin – Patricius). The Historian David Rollason has suggested that this was held by only one person at a time and we may be able to look at is as equivalent to a similar top role in the Merovingian court (France), called there the ‘Mayor of the Palace’. So we can imagine a top minister and chief advisor to the king. Next in status appears to have been the Ealderman and the historian Alan Thacker has suggested that some eight of these were present in Northumbria at a time. These were great lords, some even of royal descent (or the descendants of older royal dynasties that had lost their royal status) that may have governed a region or district. In later times this rank came to be associated with the title of Earl, a name borrowed into Old English from Old Danish. Beneath the Ealdermen were royal thegns – or gesiths – high ranking warrior aristocrats who held office at court or in the royal army. The reeves that ran royal palaces were likely drawn from this tier of society. We hear from the Life of St Wilfrid that one of these was the administrator of the Royal Palace of Dunbar at the time of King Ecgfrith, when the king instructed him to imprison Bishop Wilfrid there.

In the 10^th century the ruler of Bamburgh was referred to as a ‘high reeve’ and in the 11^th century its rulers were often called Ealderman or Earls. So its possible that a site as important as Bamburgh may have had a reeve of particularly high status drawn from the highest levels of society just below the kings themselves.

Kings of the North after AD 867

We can trace the royal line of the north – that ruled what is now Northumberland and Durham, and likely parts of the north west of the Pennines, into the last decades of the 9^th century after the partition of the kingdom and the creation of a Viking kingship in York.

He had clearly not come recently to power and was noted (in the history of the Church of Durham a text preserved at Durham Cathedral that has much information from the early medieval period) as a friend and ally of Alfred the Great who died in 899. The short note that tells of his death (preserved as a kind of historical apocrypha by the Church of Durham) tells us he was murdered by another great noble of the north.

We have the names of three kings following Aella. Ecgberht, the puppet king placed in power by the Great Army and two of his successors who, it seems, successfully reasserted some independence for the lands north of the Tees. These were likely descendants of the royal house (though perhaps a rather extended royal house) if not necessarily the children of the two rival kings who died in 867.

The Bamburgh ruling house appears in the historical record at the beginning of the 10^th century. The first of the Alderman/High Reeves whose names are directly associated with Bamburgh, and who were clearly rulers of great substance within the region, is named Eadwulf. Annals in England but also significantly as far as Ireland noted his death in AD 913. The chronicler Aethelweard names him as reeve of Bamburgh, demonstrating the link to the royal place dates from at least this period. He was clearly important enough for his death to be recorded far and wide and it is also fascinating and informative that the titles used for him in the Irish annals were those used by them when reporting the death of the old kings of Northumbria. Proof if any were needed of his status and power.

The appearance of the Bamburgh family

Assuming Ecgberht II ruled for several years that would take us very close to the time that Eadulf was the important ruler and ally to Alfred the Great. This does not mean that Eadulf was Ecgberht II’s formal successor, or direct descendent, but it may suggest that he inherited the role of the pre-eminent ruler of the lands to the north of the Tees by some form of arrangement or even by the fact of being the most powerful of the magnates of the region. This is not much removed from the little we know of the contested royal successions we see between rival branches of the royal dynasty in the 8^th and earlier 9^th centuries. At that time ambitious potential heirs seem to have competed for power by cultivating support from other powerful figures that included great lords and the major Bishops. Perhaps Eadwulf arrived in power in a similar way being a substantial land owner with a military force and the backing of some other important players.

One thing that does seem certain is that from the first Eadulf taking power north of the Tees, with few exceptions, power lay in his hands and his successors, who were his descendants. The nature of rule in the north changed and the era of competing dynasties was over as succession stayed within the family and seems in the main to have been orderly.

Where did Eadulf come from?

Can we then see Eadulf as the successor of one of the extended competing branches of the royal dynasty, who successfully did away with rival branches, or was he just an outsider without any sense of a legitimate claim who took control through force? There is a surviving text that claims to preserve his family origins. This is a manuscript now at Cambridge University Corpus Christi College – called MS 92. It contains a continuation of an annal by John of Worcester that preserved a series of additional documents tacked onto the end and one of these was the genealogy of Earl Waltheof, a descendent of the historical Uhtred (see our previous blog) through the female line. This genealogy names our first Eadwulf (who died in 913) as the son of a daughter of King Aella, and so a descendant of his dynasty through the female line. It is not without its problems as the dynastic claims predating Aella look less than secure but the decent from Aella to the later Waltheof are completely consistent with what we know from other records and as a document it is the only one we have that links the parts of this dynasty together consistently.

This still leaves us with many questions but it does seem to give an origin story for the Bamburgh Family that we can then trace right through the 10^th and 11^th centuries. We will look at this story and how it plays out in future blogs and indeed come back to this Aella connection as it may offer some important insights into the politics of the 10^th century.