Learning to understand the dark

Rob Smith – Senior Minerals Planner

That 2020 had been unusual hardly needs emphasising. The need for adaptation and restraint in our routines has, as we all know, continued into 2021. It’s frustrating, and we all wish it could end right now, but we have to be patient a while longer.

For me, back in April and May last year when the first lockdown was at its peak, the main consolation was the lengthening hours of daylight. Combined with the glorious spring weather and the absence of traffic, it was possible to get out for a walk, bike ride, or run and experience the National Park (or at least that little bit of it near my home) as never before. Some of the reasons we all love it – its diverse landscapes, the wide sweeps of heather moorland, its tranquillity and sense of remoteness, the valleys, forests, and of course it’s wildlife – were all brought into sharp focus in a way that I’d not quite experienced until then, and they seemed more valuable than ever. It wasn’t just the long hours of sunshine; more what the place meant to me during that difficult time.

Sometimes we know instinctively that something, or someone, is special even if we can’t put a finger on just why. But when it comes to a place, as for many things, getting to the bottom of this sometimes tricky question is a critical first step towards being able to look after it in way which ensures its intrinsic value is retained for the future.

The North York Moors National Park Authority has tried to identify exactly what it is that makes the area such a special place. These ‘special qualities’ help us describe and understand why it is so valuable and why it needs protecting. They include those qualities I was enjoying on my lockdown excursions in spring but there are many more, in fact twenty-eight in total. All are equally important, even if we each have our own favourites.

NYMNP Special Qualities (from 2012 Management Plan)

Importantly, promoting opportunities for the understanding and enjoyment of the special qualities of the National Park by the public is one of the two main statutory purposes of a National Park Authority. Alongside the other main purpose, to conserve and enhance natural beauty, wildlife and cultural heritage, it drives much of what we do as an organisation.

Last year spring turned into summer and then autumn brought lockdown mark two, and this time it was different. The long days of sunshine seemed quite distant. It was dark before the end of the working day and opportunities to get into the outdoors were much harder to find. Chances are when daylight and opportunity coincided, the weather wasn’t cooperating. Which brings me back to the need for adaptation.

One of the National Park’s special qualities is its ‘dark skies at night and clear unpolluted air’. Recently the National Park Authority has been carrying out a lot of work on the dark skies theme and you can find out more about this in previous blog posts by my colleague Mike Hawtin.

Although I’ve always enjoyed looking at the night sky, and appreciate the way that a starscape on a clear winter’s night can be just as inspiring as a beautiful landscape, or a dramatic seascape, as seen during the day, I’ve never tried to carry on with my outdoor activity at night. The thought of going off for a run through the woods or across the moors after dark for my ‘daily’ activity is a bit unsettling, however much your head also tells you there’s no rational basis for this.  But recently, that’s just what I’ve been doing.

It’s been a revelatory experience in many ways. Firstly, that I was easily capable of overcoming that irrational worry that had deterred me from trying it before. Secondly, I wasn’t the only one doing it (in a socially distanced manner)! More importantly, it has opened my eyes to a whole new sphere of ‘understanding and enjoyment’ of some of the National Park’s special qualities – sights, sounds, smells, wildlife –  that wouldn’t have been noticeable through the sensory overload that full daylight can bring. A landscape reduced in scale perhaps, but enhanced in detail and refreshingly new, even in places I’ve visited many times before.

And of course there’s the night sky. Pause to look upwards on a clear night and it’s impossible not to be impressed and inspired. Yes there’s sheer enjoyment in this, but I also feel that each individual night time visit is another step on a journey towards a better understanding of my local countryside that happens to be on the edge of a National Park, and how its special qualities meld together to make a coherent whole. I know it won’t be for everyone, but I’m pretty sure my adaptation won’t be a temporary one this time.

(Cropped) Northern Lights at Saltwick Bay. Credit Andy Dawson Photography.

Always follow the latest Government advice in regards Covid-19.

To keep up to date with the latest National Park situation in regards Covid-19 – see here.  Hang On – Stay Local – Keep Positive.

What’s Ironstone?

Tom Kearsley – Mineralogist

Iron is arguably the most important metallic element in the history of human technology. In the most comprehensive modern reference volume on properties, processing and use of metals – the Metals Handbook edited by Davis, 1998 – there are more pages devoted to ‘ferrous’ metals (‘irons’, steels and high performance alloys) than to all of the other metals combined.

Together with Magnesium (Mg) and Aluminium (Al), Iron (Fe) is an abundant element throughout the Solar System (Lodders, 2010), including the Earth. It was inherited from dust created by ancient giant stars, then brought together over four and a half billion years ago during the formation of the planet from the collision of asteroids and meteorites in the early Solar System. Much of the Earth’s Fe, along with Nickel (Ni) and Sulfur (S), is now in the core where it is responsible for the magnetic field of the planet. ‘Iron’ is also occasionally found on Earth’s surface as a ‘native’ metal, this may come from meteorite falls (which will not be pure Iron element, but will also contain a little Ni), and even a little can be found in some volcanic lavas. This raw material has been used by people for at least 5000 years, but it is so rare that ‘iron’ was not the most widely used metal until much later. In nature, Mg and Al readily form common minerals with Silicon (Si) and Oxygen (O), but they are not found as metals without human intervention, and they have only become widely manufactured and used in the last century.

Although now a little dated, ‘Metals in the Service of Man’ by A. Street and W. Alexander (10th edition, 1994) provides a concise and readable introduction to the sources of metals, their processing, properties and uses. An excellent and detailed explanation of how metals (including ‘irons’) came to be produced, from the earliest methods up to modern large-scale industries, can also be found in ‘A History of Metallurgy’ by R. F. Tylecote (1992). The first widespread use began with discovery that Copper (Cu), and later Tin (Sn) could be extracted relatively easily from their ore minerals, giving rise to the ‘Bronze Age’, beginning perhaps 9,000 years ago. It is likely that the discovery of ‘iron’ smelting was accidental, perhaps around 4,700 years ago, and was possibly linked to the use of Iron-rich material in production of copper. By 3,000 years ago, ‘iron’ was important in human societies, being used widely in making weapons.

To produce ferrous metal in quantity, it’s necessary to find a good supply of a suitable starting material – the ore. Fuel is required to break the ore down into elemental Iron, typically by raising it to a very high temperature, away from air. It’s also important to be able to remove a range of impurities from the molten metal. Improvements in smelting technique have long been driven by pressures of the cost of mining and transporting ore and fuel, but also reflect the availability of different types of ore. Since the Second World War a very unusual type of ore, Banded Iron Formation (BIF) has been mined in enormous quantities in Australia, Brazil, the USA and Russia (among other countries). BIF is a very peculiar sedimentary rock, deposited in ancient seas, more than two billion years ago when the atmosphere and oceans had very different behaviour to the modern world. Because it is available in large quantities (many millions of tonnes per annum) and can be processed quite easily to concentrate the content of Iron, it is now most economic to transport this ore worldwide, rather than smelting at source in areas lacking fuel. Before the use of BIF, most production usually relied upon local supplies of ore, as well as coal, coke or charcoal, and additives to help separate metal and slag. In Britain, we have no BIF, and there’s little in Europe as a whole. The history of ferrous metal production in Britain therefore reflects making do with what was available, and many different types of Iron-rich rocks (ironstones) were used as ore.

Example of 'Ironstone'

The most common natural Iron-rich materials found on the modern Earth’s surface are oxide minerals, carbonates, sulfides and fine aluminosilicates. The oxides may be loose mineral grains from weathering of igneous rocks such as basalt lavas, or may form by reaction of volcanic glass and Iron-bearing silicate minerals (such as olivine or pyroxene) with Oxygen and water, especially during tropical weathering. Two minerals are often formed : Goethite (yellow-brown oxyhydroxide, FeO.OH, about 60% Iron by weight) and Hematite (red-purple-grey oxide Fe2O3, nearly 70% Iron by weight), both contain Iron in an oxidised form, Fe3+, which is not very soluble in water. As anyone who has owned an old car will know, metallic ‘iron’ and steel are also able (and all too willing) to form similar oxidised rust! The insoluble oxyhydroxides and oxides are very widespread as tiny grains in soils, giving brown or red colouration. Accumulation in dense soil layers can produce material suitable for use as ore, but these minerals were also occasionally deposited from warm water flowing through cracks in rock, and may form patches and veins of very high grade ores, such as the red Hematite ‘kidney ore’ of Egremont in Cumbria. BIF contain mainly Hematite, in layers with silica.

However, if the tiny grains are washed away by streams and rivers until they reach still water, they can sink and become gently buried within muddy sediment in a lake, delta-front or quiet-water sea. Here they are effectively cut off from air, and as bacterial decay of organic matter in the mud proceeds, they may again lose Oxygen, releasing soluble Fe2+ ions. In freshwater, the ‘reduced’ soluble Iron may react with carbonate created by bacterial oxidation of organic matter (such as rotting leaves), and can be fixed as an insoluble carbonate mineral called Siderite (FeCO3). This often forms spherical concretions that may become flattened as the muddy layers are gradually squashed by continuing build-up of sediment above. The hardened (lithified) concretions or nodules are grey-green when broken, although may turn brown on weathering. Often found in mudstones between coal seams of Carboniferous age across Britain, these Siderite nodules (called ‘doggers’ by miners) may contain nearly 50% Iron by weight, and were an important source of ore during the Industrial Revolution of the seventeenth and eighteenth centuries.

Iron-rich mud deposited in seawater may behave differently. The oxides and oxyhydroxides again release soluble Iron as Fe2+ ions, but bacterial activity near the surface of the accumulating sediment removes Oxygen from the sulfate ions in the seawater, creating sulfide ions. This is how disturbed marine muds often come to smell of ‘rotten eggs’, the characteristic signature of hydrogen sulfide (H2S). Soluble Fe2+ reacts very quickly with sulfide ions, forming a black iron sulfide, and eventually golden Iron Pyrites (FeS2), with about 45% Iron by weight. This can be used as an Iron ore, but releases acidic sulfur dioxide fumes during processing, and requires both careful handling and large amounts of fuel. However, if deposition of mud is quite rapid, the production of sulfide can stop well before all of the soluble Fe has reacted, and more of the carbonate Siderite will then form, often becoming the main Iron-bearing mineral in shallow marine ironstones.

Iron may also be found in pale green hydrated aluminosilicate minerals (containing Al, Si and water), these are members of the Clay Mineral and Chlorite groups, called Berthierine and Chamosite, typically containing about 25% Iron by weight. How these minerals form is still not well understood, despite many studies of ancient and modern ironstones (Kearsley 1989; Young, 1989; Mücke and Farshad, 2005; Clement et al., 2019). There are probably several different origins. Some may be formed by soluble Fe reacting with the white clay mineral Kaolinite within the mud, or from insoluble Fe oxides reacting with Al and Si hydroxides. Some may form by tiny crystals growing within a slimy gelatinous blob or layer, some may grow as crystals directly from water in the mud. Strangely, these minerals also seem to favour growing in layers around a central core, making a concentric tiny egg, an ‘oolith’ or ‘ooid’. When ooids/ooliths are common within an iron-rich rock, it is described as an oolitic ironstone. It is not uncommon to find ironstones that contain aluminosilicates, Siderite, Hematite and Pyrite all together, including within ooliths/ooids – even with evidence that these minerals have replaced each other during or after deposition of the layer.

Rosedale SEM (Scanning Electron Microscopy) Minerals - copyright Tony Kearsley

Oolitic ironstones are complicated rocks (see figure above). As their content of Iron can vary a great deal, they may or may not prove to be an economic source of Iron, which may also depend upon the other materials that they contain. High contents of Calcium (Ca) may help smelting, but high Phosphorus (P) can contaminate the metal that is produced. The oolitic ironstones mined in Rosedale and around all of the North York Moors typically contain mixtures of Siderite and Berthierine, as well as Kaolinite and the Calcium carbonate mineral Calcite.

The oxide Magnetite (Fe3O4) may also be found in some oolitic ironstones, it contains over 70% Iron by weight. As the name suggests, this mineral is strongly magnetic, unlike almost all of the other Iron ore minerals. It is quite common in Mg- and Fe-rich igneous rocks (formed from molten material), and can occur in massive deposits with a very high percentage of Iron. For example, magnetite has long been mined in Sweden, and was much sought after by both Allied and Axis industries during the Second World War. Magnetite is well known to occur in rocks that have been subjected to burial heating (low grade metamorphism), probably growing as coarser crystals from iron carried through porous rock by hot water.

However, it has also been found (and almost completely mined out) in sedimentary ironstone deposits in Rosedale, it was so rich in Iron. Here its origin is still a mystery, and there have been differing interpretations of when and how it formed. There are several 19th century accounts of the discovery of magnetic ores in Rosedale (Bewick 1861; Wood, 1969; Marley 1871), as well as descriptions of these rocks in the Geological Survey Reports of Hallimond (1925) and Whitehead et al. (1952). From other evidence in the North York Moors, it doesn’t seem likely that these rocks were heated sufficiently to encourage metamorphic magnetite replacement of other minerals, and these are definitely not rocks formed from hot melt. Perhaps the peculiar setting where these sedimentary ironstones accumulated was an important factor in creating Magnetite? The earlier accounts suggested that the richest ore was found within elongate troughs, eroded into the underlying layers. Young (1994) suggested that there were indeed shallow basins where ooliths were deposited, but that the basins had been formed by fault motion at about the same time. Is it possible that stagnant water saturating the sediment within these hollows allowed Magnetite to form, replacing other more-oxidised Iron-rich minerals?

Ironstones deposited during the early part of the Jurassic Period have been extensively mined throughout England and Western Scotland, as described in Whitehead et al. (1952). There is a wider discussion of other ironstones from a broader range of ages, across England and Wales, in Hallimond (1925).

References

Bewick, Joseph 1861. Geological Treatise on the District of Cleveland, in North Yorkshire, Its Ferruginous Deposits, Lias, and Oolites; With Some Observations on Ironstone Mining. London: John Weale

Clement, A. M., Tackett, L. S., Ritterbush, K. A. and Ibarra, Y. 2019 Formation and stratigraphic facies distribution of early Jurassic iron oolite deposits from west central Nevada, USA. Sedimentary Geology 395 C Web. doi:10.1016/j.sedgeo.2019.105537.

Davis, J. R. (Ed.) 1998 Metals Handbook 2nd Edition. ASM International, Materials Park, OH 44073-0002, USA. i-xiv, 1521 pp. ISBN 0-87170-654-7.

Hallimond, A. F. 1925 Iron Ores: Bedded Ores of England and Wales. Petrography and Chemistry. Special Reports on the Mineral Resources of Great Britain. Volume XXIX. HM Stationery Office, London. p 75, plate IV fig. 14.

Hawley, D. 2019 Rosedale – the magnetic ironstone conundrum. Field Excursion Notes. The genesis of geology in York and beyond. Yorkshire Philosophical Society and Geological Society of London History of Geology Group. 25th Anniversary Meeting Thursday 24th October 2019. Downloaded on 3rd December 2020 from: https://www.ypsyork.org/wp-content/uploads/2020/02/HOGG-YPS-YORK-Rosedale-Magnetic-Ironstone-Conundrum-Oct-2019-ONLINE.pdf

Kearsley, A.T. 1989 Iron-rich ooids, their mineralogy and microfabric; clues to their origin. In Young, T.P. and Taylor, W.E.G. (Eds) Phanerozoic Ironstones. Geological Society of London Special Publication 46:141-164.

Lodders, K. 2010 Solar system abundances of the elements. In: Principles and Perspectives in Cosmochemistry. Lecture Notes of the Kodai School on ‘Synthesis of Elements in Stars’ held at Kodaikanal Observatory, India, April 29 – May 13, 2008 (Goswami, A. and Eswar Reddy, B. eds.) Astrophysics and Space Science Proceedings, Springer-Verlag Berlin Heidelberg. p. 379-417 ISBN 978-3-642- 10351-3.

Marley, J. 1871 On the Magnetic Ironstone of Rosedale Abbey, Cleveland. Transactions of the North of England Institute of Mining and Mechanical Engineers. 19, 193-199.

Mücke, A. and Farshad, F. 2005 Whole-rock and mineralogical composition of Phanerozoic ooidal ironstones: Comparison and differentiation of types and subtypes. Ore Geology Reviews 26:227–262.

Powell, J. H. 2010 Jurassic sedimentation in the Cleveland Basin: A review. Proceedings of the Yorkshire Geological Society 58:21-72.

Street, A. and Alexander, W. 1994 Metals in the Service of Man. 10th Edition. Penguin Books Ltd, London, UK. ISBN 10: 0140148892

Tylecote, R. F. 1992 A History of Metallurgy 2nd Edition. The Institute of Materials. 1 Carleton House Terrace, London. 255 pp. ISBN 0-901462-88-8.

Whitehead, T. H., Anderson, W., Wilson V., Wray, D. A. and Dunham, K. C. 1952 The Liassic Ironstones. Memoirs of the Geological Survey of Great Britain. Department of Scientific and Industrial Research, Her Majesty’s Stationery Office, London. pp 47-50.

Wood, N. 1869. On the Deposit of Magnetic Ironstone in Rosedale. Spons’ Dictionary of Engineering, Part VIII (Borings and Blasting), pp 501 – 512.

Young, T.P., 1989. Phanerozoic ironstones: an introduction and review. In: Young, T.P. and Taylor, W.E.G. (Eds.), Phanerozoic Ironstones. Geological Society of London Special Publication 46: ix-xxv.

Young, T. P. 1994 The Blea Wyke Sandstone Formation (Jurassic, Toarcian) of Rosedale, North Yorkshire, UK. Proceedings of the Yorkshire Geological Society 50:129-142.

Dark Skies (Part Two): We need to talk about ALAN

Mike Hawtin – Head of Polyhalite Projects

Dalby Playground Iridium Flare by Steve BellEnjoy the National Park after dark
It’s probably as a result of increasing light pollution in urban areas that many more people are seeking out opportunities to experience Dark Skies, which is resulting in a growing interest in Astro Tourism.

We know from the popularity of our very own Dark Skies Festival that increasing numbers of residents and visitors to the National Park value dark skies and love to take part in all manner of outdoor events at night. Started almost six years ago, in partnership with the Yorkshire Dales National Park, the Festival has become the biggest in the country and is contributing significantly to the local economy during what is typically considered the low tourist season. This helps businesses survive through winter and doesn’t add to the busy summer season. The Festival in 2020 attracted over 8,000 attendees to over 100 events and across a two week period and contributed over £300k to the local economy in the North York Moors alone.

The ongoing success of the Festival led to a decision by the National Park to seek worldwide recognition by joining a select group of organisations around the globe in applying for International Dark Sky Reserve status. There are key requirements to becoming a Dark Sky Reserve along with ongoing obligations to maintain the status. These include meeting specific requirements for the quality of our dark skies, organising continued education and outreach events, control of new lighting and making ongoing improvements to existing lighting.

This lengthy process started three years ago with a huge amount of background work including audits of the type of lights and controls used in the National Park along with their colour temperatures and taking dozens of dark skies meter readings to identify where our darkest areas are. We’ve even had support from local and regional councils to install only Dark Skies compliant street lighting at 3000k or less.

This work has fed into the creation of a Lighting Management Plan which will help us ensure that new lighting will meet Dark Skies criteria. We’ve also had letters of support from dozens of parish councils, landowners, organisations, astro groups, businesses and pledges of support from the public, which have all been included in our application.

STOP PRESS – This month we were designated an International Dark Sky Reserve, along with the Yorkshire Dales National Park, one of only 18 in the world.

Dark Skies Lighting Improvement Scheme
To help deliver improvements to existing lighting and to meet our Management Plan objectives of preserving tranquillity and Dark Skies, we’ve also set up a lighting improvement scheme to offer grants in targeted areas to help reduce light pollution. The focus will be on helping clusters of residential properties, pubs, accommodation providers, campsites and visitor centres etc. to become exemplar sites for Dark Skies friendly lighting.

This scheme is being funded by section 106 payments from the Woodsmith Mine development to compensate and mitigate for the negative impacts of the mine development. We’re working on a number of demonstration projects to help property owners understand that it’s not about turning off all lights but about sensitive and efficient use of artificial light at night. Two of these projects have already been delivered with a number of others underway. We’ve even had requests from the Institute of Lighting Professionals and other protected areas to use images of our demonstration projects to help spread the message.

Changing lights on outbuildings from bulkheads and floodlights to downlights provides ample light for access but doesn’t create unnecessary upward light spill. Note the lack of light hitting the tree in the second image above.

Glare from poor lighting in a service compound is reduced, eliminating upward light spill.

Changing floodlights or angling them down provides enough light for operational purposes (in this case loading) whilst at the same time reducing glare and unnecessary light spill.

In recent weeks, we’ve set up a new volunteer role called Dark Sky Monitor and it’s really exciting to announce that the first recruits to this role have attended a live online training session so they are ready to go when restrictions allow. During the session they learnt about why Dark Skies are important, how we can protect them and how to use a tiny box of tricks to take readings which will be added not just to our records but also to an international database.

If you’re reading this and wondering how to do your bit by converting or adjusting your outside lighting, whether it be for reducing energy usage (and cost), stargazing, wildlife or your own health and wellbeing, there are some easy steps to follow…

Light only what you need

Is the light needed? Is it purely or partially decorative or does it serve a specific purpose?
Can I angle floodlights down, shield them or change to downlighting?
Is light projecting beyond my boundary and causing a nuisance for others?
Can my light(s) be seen from a great distance? This gives a good idea of how they are positioned.

Light only when you need it

Are my lights on a timer or a sensor? Consider fixtures where the sensor can be angled independently of the light.
What time do they come on and go off? Ideally 10pm is a good curfew or use of a proximity sensor is even better.

Light only at a level suitable for the situation

How bright are my lights? Unless for operational purposes, one or two lights at a maximum of 500 lumens are usually enough for most residential properties.
Am I using warm white light? Don’t forget that all lights should be no more than 3000k and preferably 2700k.

Milky Way over Ravenscar by Steve BellWe’ve created a Dark Skies Friendly lighting page with a link to a property lighting audit to help guide you through the process. We’d love to see some before and after images if you decide to make some changes.

Keep an eye out on our Dark Skies webpages and social media for information and updates on best viewing spots, events and activities, and announcements.

We hope you’ll continue to follow the ongoing work to protect the Dark Skies above the North York Moors National Park and don’t forget to talk to others about ALAN.

Dark Skies (Part One): We need to talk about ALAN

Mike Hawtin – Head of Polyhalite Projects

The Milky Way over Young Ralph Cross. Image: Steve Bell

Dark Skies – revered by our ancestors, a gateway to science, crucial to nocturnal wildlife and a special quality enjoyed by residents and visitors to the North York Moors National Park – are under threat.

Over 80% of people in the UK are unable to see the Milky Way, our own galactic neighbourhood. In most cities you’d be lucky to see a handful of stars due to light pollution but in truly dark places, like the North York Moors National Park, you can still see thousands. With the availability of cheap high power LED lighting though, those pristine dark skies are increasingly at risk.

You can see many cities from space but you can’t see space from many cities. Figure 22017 composite image courtesy of the U.S. National Geophysical Data Center’s Earth Observing Group. Image source: darksky.org

It’s not all bad news though. Unlike other man made threats to the natural world, this one isn’t so complex that we’re almost paralysed into inaction, we just need to talk about ALAN.

So who on earth is ALAN!? Well, ALAN stands for Artificial Light At Night and when used incorrectly and inconsiderately, ALAN can have a devastating impact, not just on our ability to enjoy Dark Skies but on animal and plant life, and even human health.

Imagine a situation where developments that interrupt or obscure our natural daytime landscapes or that impact on natural habitats and disrupt animal behaviour, were allowed to go ahead unchecked? Well that’s exactly what happens when we go to the middle of those well-known budget supermarkets to buy those cheap super bright white LED lights and put them up around our property. These lights are designed to flood the outside of our homes and garden with simulated daylight, often causing significant glare and nuisance to others, both near and far.

Understandably we can be quite protective of our need for light at night. Let’s face it, we all need it, whether it’s for safe working, recreation, getting to our front door with shopping bags and children in tow or for general feelings of security. At the same time though, we can probably all think of poor examples of lighting, from inconsiderate neighbours keeping us awake into the night, car sales forecourts dangerously dazzling us when driving past, long after closing time or that one floodlight we can see for miles in an otherwise dark and tranquil remote landscape.

The impact of a single farm floodlight on the night sky during a stargazing event (image: Richard Darn)

The rhythms of life
The impacts of light pollution go much further than ‘just’ causing a nuisance. It prevents us from seeing something humans have been able to see for thousands of years, something that has inspired humans to seek to understand our place in the universe, to help explain the fundamentals of science we now take for granted and even helped us navigate, long before we had maps or smartphones.

Throughout evolution, circadian rhythms, present in most living things have been responsible for natural sleep wake cycles. As daylight fades, replaced by warmer light then darkness, it signals physiological changes which signal a slowdown, which prepares us for sleep.

ALAN disrupts these natural rhythms, altering animal and plant behaviour. It can cause bats to think it’s still daylight so they stay in the roost instead of feeding and mating. It attracts moths which increases their predation and prevents them undertaking their role as nocturnal pollinators.

Research to assess the impact of artificial light on insects is ongoing. In mini-ecosystems in the Netherlands, researchers test the effects of artificial light. Credit: Kamiel Spoelstra/NIOO-KNAW.

It even disrupts the migratory behaviour of birds and the dormancy cycles of trees and plants can be altered, impacting on their ability to survive the rigors of winter. As if that’s not enough, study after study shows that too much light (especially blue light) at night also disrupts human circadian rhythms, which has been attributed to weight gain, stress, depression, diabetes and even heart disease and some types of cancer.

We know that many living things are already struggling to adapt to accelerated climate change over the past century. Widespread use of LED lighting technology though is little more than 10 years old and, through an increasing number of studies, we are just beginning to understand the impacts, which, left unchecked, could be devastating for wildlife and human health.

Conservation at the flick of a switch
It’s not often in the world of conservation, at a time when we’re tackling complex ecosystem problems, that we can legitimately say that a problem is solvable at the flick of a switch. Imagine if we could crack plastic pollution, noise pollution or vehicle pollution often with little or no cost or, if in fact that in solving the problem, we would actually save money! Wouldn’t that be something?

In the case of light pollution though, for the most part, it really can be that easy. Tilting lights down to only light where we need and switching them on only when required, and sensitively using low power LED lighting at a level suitable for the situation, will save energy and money. It will also prevent nuisance light pollution from wasted upward light and glare.

The answer isn’t simply urging us all to switch off lights though, with a bit of thought and effort, we can have the best of both worlds. By only lighting what we need, when we need it and at a level suitable for the situation, we can protect our dark skies, our nocturnal animals and even our human health whilst still having enough light to work, play and feel safe at night.

It’s all about control
Think about how you feel when you’re driving towards an inconsiderate or forgetful driver who keeps their lights on full beam, dazzling you and causing danger to other road users. It’s easy to fit a floodlight and angle it up at 45 degrees thinking it’s doing the job intended when in fact half of the light is being projected above horizontal into the sky. So with the exception of those trying to signal the caped crusader or visitors from outer space, that’s up to 50% of light completely wasted. Additionally if we look at those lights, we’re dazzled, preventing us from seeing properly, especially into the deep shadows created, which contributes to reduced safety rather than improving it.

Image source: darksky.org

It’s also understandable to think that leaving lights on all night will offer more security but it has two significantly negative impacts:

  1. It advertises our location for miles around so those unwelcome visitors looking for opportunities will know where to look.
  2. If lights are on all night, we have no idea whether somebody is meant to be there or not.

Using sensors for instance will immediately alert us if there’s an unexpected presence. If we’re concerned about animals setting them off then selecting a light with a separate sensor can help solve this by allowing the light and the sensor to be angled independently of each other.

Warm light good – Cool light bad
The colour temperature or warmth of the light is also very important. Warmer light has less impact on nature and human health. It mimics evening light (remember those circadian rhythms) as the end of the day is approaching and is much less likely to cause disruption to the natural world. Warm light also triggers feelings of relaxation, safety and welcome, most likely developed over thousands of years of sitting around the warm light of camp fires with friends and family, and feeling safe from predators.

Think about driving past that shop, hotel or pub at night and consider what looks and feels more welcoming, warm cosy light or harsh blue white light? Another impact of blue white light is that it scatters much more readily into the atmosphere which means it can cause much greater sky glow if installed incorrectly.

The colour temperature of light is measured in kelvin (k). 3000k is considered a key threshold. Below this is considered warm and over is considered cool. Dark Skies friendly lighting should have a recommended colour temperature of 2700k but where technology or availability doesn’t allow then 3000k should be considered an absolute maximum. The good news is that most lights and bulbs are available in warm white and have this specification stated on the box. It will also usually show the amount of light given off in lumens. 500 lumens is usually ample for most residential applications.

DID YOU KNOW? North Yorkshire County Council have agreed to install fully shielded streetlights with a maximum colour temperature of 3000k in our protected landscape.

Colouring in

David Mennear – Land of Iron Administration Assistant

Have a look at these two digitally ‘coloured in’ historic photographs of our local mining communities in the North York Moors, from 100 years ago.

Photograph by Thomas Smith, courtesy Beck Isle Museum. Photo colourised by: Photo Restoration Services.

Our first photograph (above) shows ironstone miners at Sheriff’s Pitt, Rosedale, getting ready for a day of hard labour in 1900. If you look closely you can notice the clothing they wore and the wide shovels they used for helping to move the heavy ironstone and scoop it into the tubs. From the tubs it was taken out of the mine and along to the nearby calcining kilns to remove the impurities to make it lighter to transport via rail on to blast furnaces in the wider region.

Photograph by Joseph Brotton, courtesy Ryedale Folk Museum. Photos colourised by: Photo Restoration Services.

The second photograph (above) was taken by J. Brotton on the 24 July 1903 – it’s of an almighty crash at the bottom of the Ingleby Incline railway. The incline is a 0.8 mile long stretch of rail to the moor top, which reaches a stonking 1 in 5 gradient at its steepest points. It was here that wagons were carefully drawn up and down the incline by a rope pulley system to allow the transport of ironstone from the Rosedale mines on to Teesside for processing into pig iron, before being transported and used across the country and the world.

Does the colourisation help make the people look more relatable? Does it make the scenes seem more immediate? Does it bring the communities of the 1900s to life?

Photos colourised by: Photo Restoration Services

Diary of a Heritage Intern

Chris Bradley – previous Building Conservation Intern

Having completed my Masters degree at the University of York I was excited to be applying for jobs and starting a new career. After a year of applying and volunteering, I Chris in his natural habitat - Ryedale Folk Museum, Hutton le Hole.was elated to get the opportunity of an internship with the North York Moors National Park Authority.

Meeting the Building Conservation team was great, they were friendly and encouraging and offered to help in every way possible whilst of course keeping to the social restrictions in place. My mentors, Maria Calderon and Clair Shields, presented a clear desire to provide a practical opportunity for new starters in the heritage sector which is something that I have found to be limited in my time searching for work.

My main objective was developing a Conservation Area Appraisal and Management Plan (CAAMP) for Hutton Le Hole. Having read and interpreted some of these official documents for past academic research I was both excited and nervous to be able to produce something that would inform and offer professional guidance whilst finally gaining experience in the career path I wanted to follow.

The first week revolved around researching the history of the village and going out to see the area in person to understand the full scope of the work. The initial research phase felt instinctual, reminiscent of my previous studies and was a comfortable start to my internship. For the initial walk in Hutton Le Hole I met up with the team to get my bearings and discuss the vision and style of the Conservation Area which helped settle my nerves as we all had similar thoughts as we walked around. The starting week was informal and friendly which helped me to quickly settle in and feel like part of the Building Conservation team.

The following few weeks I began to work on my own with supervision meetings with Chris (in the distance) appraising the beckside fencing, a feature of Hutton le Hole.Maria periodically who really helped to encourage me and regularly offered some much needed advice. Through my second week I felt my work had been making slow progress into the Conservation Area Appraisal. But I then started to create my own schedules and push myself to reach bigger targets each day. My first site visit alone felt like a big and unorganised mess, I found the hours of the day had passed but I had hardly made any progress giving me cause for concern about my deadline. However, as with everything new, this quickly changed once I had a routine and the workload soon felt manageable and was an interesting and fun job to produce and complete.

Come the sixth week I had completed a draft of the CAAMP and got the opportunity to expand my experiences with using a Geographical Information System (GIS). This is something I had only heard of briefly through my studies and through applying for jobs. I had zero experience and I believe this was just as useful to practice as the Conservation Area Appraisal process. Using the Authority’s Earthlight system, under the supervision of Nick Mason the Archaeology Officer, I was tasked with plotting and producing information for the non-designated local list for the Hutton-Le-Hole parish. This, again, was a fun task to take part in and I enjoyed the opportunity to gain the additional knowledge. I knew the Conservation Area very well at this point but now I had to expand this to the whole parish, being able to explore and research the wider setting was now easier having gained the experience of recording the data for the Conservation Area already.

Hutton Le Hole by Chris J. Parker.

By my final week I had completed the Conservation Area Appraisal documents and the non-designated local list. So I got the chance to review and discuss planning applications with Maria. This gave me an insight into how the Building Conservation Team works on their more regular tasks, giving me more opportunities than planned within the time of my internship.

My internship was a fully positive experience and offered more than I expected in the time frame. I am very grateful to have been given the opportunity by Maria and Claire and I feel I have built strong relationships with them both within the short period of time at the North York Moors National Park Authority. I hope this can become a regular internship there where they can offer more experiences and, more importantly, encourage others to get involved in heritage.

Band of Six

Our Ryevitalise Landscape Partnership Scheme has been active now for over 16 months; it’s had quite a time so far. We thought it would be courteous to introduce the very adaptable delivery team.

Upper reaches of the Rye catchment. Copyright NYMNPA.

“I’m Alex, the Programme Manager for Ryevitalise. My main role is to work closely with all of our wonderful partners and the National Lottery Heritage Fund to deliver our Ryevitalise vision to ‘conserve, enhance and restore the natural and cultural heritage of the area, enabling people to reconnect with the history, wildlife and landscapes of the River Rye and its tributaries’.

I’ve always had a passion for nature. Growing up locally I have great childhood memories of taking part in lots of activities with the North York Moors National Park. In my early teens my family moved to the Falkland Islands where I was fortunate to volunteer for Falklands Conservation, spending days on end undertaking penguin chick census checks … it was amazing! My family then moved to Ascension Island where I carried out bird, turtle and endemic plant counts, and these experiences led me to pursue a career in conservation.

Alex Cripps, Ryevitalise Programme Manager. Copyright NYMNPA.I studied Environmental Science at the University of East Anglia, including a year in Canada – my dissertation focused on the impacts of habitat fragmentation on ungulates (moose, elk and deer) near Banff National Park. I then spent two years travelling and working in New Zealand before I decided I’d better get a ‘real’ job.

I was delighted to be offered a job in 2013 working for the North York Moors National Park as their Conservation Graduate Trainee. Since then I have developed a huge passion for rivers; I became the Esk and Coastal Streams Catchment Partnership Officer in 2014 before taking on the role of Ryevitalise Catchment Restoration Officer in 2017, part of a small team to develop Ryevitalise. In 2018 the final Ryevitalise application was submitted and now here we are, delivering this ambitious landscape partnership scheme and it’s great to be leading the team as Programme Manager.

I love sharing my enthusiasm for rivers and the fascinating wildlife that our freshwater habitats and surrounding areas support. For those of you who know me you will know that I absolutely love aquatic invertebrates – one of my favourite moments in the Rye catchment was watching mayflies dancing above the River Rye near Helmsley, there’s nearly always a dipper bobbing about here too.

Ryevitalise will be raising the profile of rivers, looking at how valuable these ecosystems are and how important they are to local communities. We will be working alongside local communities, including land managers and young people, reconnecting people to their local river systems and exploring how simple every day actions to help care for our rivers can collectively make a huge, positive difference. So it’s great to be underway, delivering a wide variety of projects, and I look forward to meeting some of you soon!”

Mayflies dancing above the River Rye near Helmsley. Copyright Alex Cripps, NYMNPA.

“Hi everyone. My name’s Paul Thompson and I’m the Programme Officer for Ryevitalise currently overseeing our ancient woodland restoration work, access improvements, and community arts project. I’ve also been supporting land managers in Bilsdale carrying Paul Thompson, Ryevitalise Programme Officer. Copyright NYMNPA.out habitat improvement works. I’ve been really inspired by our community who care passionately about our local heritage and rural landscape. Finding solutions to key conservation challenges that benefit people, the economy and the environment is incredibly rewarding, and demonstrates the power of National Lottery Heritage Fund’s landscape partnerships.”

View of Hawnby Hill. Copyright Paul Thompson, NYMNPA.

“Hello! I’m Amy, Ryevitalise Education & Engagement Officer; my job is exactly what it says really. Anything from working with schools, volunteers, local communities, running events and bit of historical work thrown in for good measure!

I started conservation life as a seasonal ranger for the National Trust on the lovely South East Cornish coast. Then moving closer to home to work for the Tees Valley Wildlife Trust as part of the River Tees Rediscovered project. All my roles have involved people (and rivers) in some way! Whether it’s bossing… I mean working with… volunteers; mammal surveying, running community events or working with local people of all ages. I love seeing folks reaction to the first path they have built, catching their first tad pole or that first cup of tea after a gruelling task. It’s amazing how inclusive conservation can be; wildlife doesn’t care who you are or what you can do.

Having spent many of my days as a teenager walking the Cleveland Way and hiking up Hasty Bank, it’s great to actually work here and show off what a lovely place the Ryevitalise area is!”

Cleveland Hills from Urra Dyke at top of Rye Catchment. Copyright Simon Bassindale.

“Hi! I’m James and I’m the Catchment Restoration Officer. Essentially my job involves working to improve the water quality of the River Rye by engaging with land owners, whether by creating conservation agreements which typically address point source James Caldwell, Ryevitalise Catchment Restoration Officerpollution issues, promoting opportunities to increase habitat connectivity, controlling invasive species, or helping to create a more natural river by removing obstacles to fish migration.

I had a rural upbringing and have always had a passion for the environment which is reflected in my career choice, starting as an assistant ranger for a trust in Peterborough, moving to a countryside ranger position with a borough council in Surrey and most recently settling at the North York Moors National Park Authority. 

I enjoy exploring, whether walking, running or cycling, and am delighted to have such variety on the doorstep that also forms my wider “office” and supplies great photo worthy content.”

Byland Abbey. Copyright NYMNPA.

“Hi everybody! I’m Sam Lewsey, the Field Officer for the Ryevitalise project and my main areas of responsibility are the citizen science programme, and the delivery of practical works with our wonderful volunteers.

Sam Lewsey, Ryevitalise Field OfficerI came to the North York Moors from the National Trust, where I worked as a Ranger for the last few years, and before that I worked for Cambridge University. Both my parents had a huge love of the great outdoors and natural history, and this was something I picked up from an early age. I am passionate about wildlife and love working with volunteers setting up programmes of surveying – developing my own ID skills and helping others develop theirs. Hay meadows and their associated pollinators hold a particular fascination for me. When not crawling about looking at wildflowers and fungi you’ll find me out on a run – the longer and hillier the better!

If you’re keen to get involved in volunteering with us please give me a shout and I can talk you through the opportunities that are available within this fantastic scheme.”

Riparian woodland in autumn, near Hawnby - copyright Paul Harris, NYMNPA

“Hi everyone – my name’s Ann Pease and I am the Administration Assistant for Ryevitalise, overseeing all of the background paperwork that keeps the project ticking Anne Pease, Ryevitalise Administration Assistantalong! One of my many roles is liaising between the team and the National Lottery, helping to collate and provide the evidence needed to receive our funding. 

I’ve volunteered for many years across the conservation sector – and am over the moon to be able to work on a project having such a positive effect on our areas landscape and wildlife. 

Being a local girl I am deeply connected to this landscape – I’ve spent much of my life up on the North York Moors and it’s great to see this project champion what makes the area so special. 

If I’m not working you’ll probably find me out walking somewhere – I am a big fan of National Trails and long distance walks…I am also a big fan of butterflies, moths and birds of prey and never miss a chance to have a bit of a geek out!

At the moment I am on maternity leave having had a baby boy in July (mid lockdown!), so am watching from afar – but am very much looking forward to being back in February to see how the project is getting on…”Ryevitalise logo banner

No lockdown for Ring Ouzels

Vic Fairbrother, Ken Hutchinson and the Updale Natural History Recorder

We have been studying Ring Ouzels on the North York Moors for over 20 years. This has involved intensive fieldwork every week throughout each breeding season, commencing before the birds return from North Africa in order to establish first arrival dates. Courtship behaviour, nest building, egg laying, the hatching and fledging of chicks and levels of predation have all been carefully monitored. Simple and complex song was also recorded and analysed and the presence of a local dialect established. Conservation measures were identified and implemented. Although our intensive study had ended, we had hoped to continue to maintain a general overview of the Ring Ouzel’s foothold on the North York Moors again this year.

An early indication of problems ahead came when the annual meeting of the UK Ring Ouzel Study Group in Penrith on 21 March this year was cancelled in view of the imminent pandemic lockdown. Shortly afterwards, the BTO and RSPB suspended all survey work, nest monitoring and bird ringing and it became clear that our own observations were also going to be severely affected.

Although our ability to monitor them this year has been severely disrupted, this remarkable bird’s annual struggle for survival has continued on our doorstep.

It was sunny with a cold wind in Rosedale on 21 March and with travel about to be severely curtailed, it was cheering to watch Curlews and Lapwings back on their upland breeding grounds but even more special was the sight of two Wheatears which are often the first migrants to arrive back in the dale. Sudden chacking at Nab Scar then revealed the exciting sight of the first Ring Ouzel of the year to return to Rosedale from their winter quarters.

Wheatear, Rosedale. Copyright Vic Fairbrother, Ken Hutchinson and the Updale Natural History Recorder.

As more ouzels gradually returned to local sites, small groups of ouzels (presumed to be passage birds i.e. migratory birds on their way to somewhere else) were also reported from a number of locations during much of April.

With restrictions still at a high-level, the permitted daily exercise walks provided a real treat on 29 April, when a female Ring Ouzel was observed gathering nesting material at Sturdy Bank and taking it to a suspected nest site whilst the male was singing nearby. A week later, the female flew into this suspected nest site where she remained and was presumed to be sitting on eggs.

Ring Ouzel, Rosedale. Copyright Vic Fairbrother, Ken Hutchinson and the Updale Natural History Recorder.

During the next few weeks, territorial behaviour by two more pairs of ouzels was also reported from Reeking Gill and Reeking Gill South and with the easing of restrictions in mid-May, slightly more detailed monitoring was enabled.

An increasingly rare sight and an experience to treasure occurred on 27 May, when a pair of Cuckoos flew in towards Reeking Gill, the male calling beautifully. When he came to the south end of the embankment a male ouzel promptly chased it away. A few minutes later the male Cuckoo returned to land on a rock just inside the entrance to the gill. As walkers approached, he flew higher up the gill to land in the rowan tree opposite a first brood nest site, at which the second male ouzel immediately chased it down and out of the gill.

Cuckoo, Rosedale. Copyright Vic Fairbrother, Ken Hutchinson and the Updale Natural History Recorder.

Three days later two female ouzels were being closely watched at Reeking Gill. A male and at least two fledglings could be seen below the first brood nest site high on the north east side when one female flew up the gill and straight into a new and presumed second brood nest site, almost opposite the first brood nest site and close to where the Cuckoo had been evicted on 27 May. To our great surprise the second female then gave her nest site away by flying straight in to heather just outside the south east entrance of the gill and in the vicinity of the other Cuckoo altercation. The discovery of these new nest sites explained the agitated behaviour of the two male ouzels towards the Cuckoo a few days earlier. Later, the two male ouzels were heard counter-singing.

The welcome easing of restrictions eventually enabled eight nestlings to be fitted with BTO rings at Sturdy Bank and Reeking Gill. The three nests here and the one at Sturdy Bank all fledged young but a nest at Reeking Gill South was predated. Fledged young were also seen at Bank Top, Hob Crag and Blakey on the west side of Rosedale, along with a number of rather inconclusive ouzel sightings. In view of the many constraints it is almost certain that other breeding attempts went undetected in the study area this year.

Rosedale. Copyright Vic Fairbrother, Ken Hutchinson and the Updale Natural History Recorder.

Ring Ouzels switch to eating berries as they prepare for migration and during our study, we had become concerned at the lack of regeneration among the scattered rowan trees in the study area.

The Ring Ouzel’s remarkable link with the industrial heritage in Rosedale was recognised during the Land of Iron Landscape Partnership Scheme, funded by the National Lottery Heritage Fund. We were delighted when as part of a number of biodiversity initiatives a small-scale tree planting project was developed in an attempt to provide a sustainable supply of rowan berries here.

Land of Iron Landscape Partnership Scheme logo banner

Mature Rowan Trees, Rosedale. Copyright Vic Fairbrother, Ken Hutchinson and the Updale Natural History Recorder.It was a sunny day but with a strong chill breeze from the south west when on 3 September we decided to check how well the rowan tree planting was faring. There were widespread reports of good berry crops elsewhere and as we descended below the railway track and worked our way towards Blakey Swang from the south, we could see that the surviving mature rowan trees here were a splendid sight.

We then turned our attention to several small enclosures and scattered individual saplings carefully placed in the vicinity of mature trees along the steep escarpment. In some of the small enclosures we could see that numerous strong saplings had grown well above the tree guards. Vic pointed out a particularly healthy group in one of the highest enclosures and Ken looking through binoculars observed that one bore a small clump of berries. At first, Vic thought that he was joking but the first fruits of the planters’ efforts were there on display. He could not resist the impulse to climb the steep bank for a photo.

Growing Rowan Trees, Rosedale. Copyright Vic Fairbrother, Ken Hutchinson and the Updale Natural History Recorder.

The full story of this 20-year study by Ken and Vic has now been published and can be enjoyed in The Ring Ouzel: a view from the North York Moors launched this month by Whittles Publishing. Illustrated in full colour throughout and enhanced by superb paintings by local wildlife artist Jonathan Pomroy copies may be ordered at www.whittlespublishing.com  or obtained from the Moors National Park Centre, Danby or from Sutton Bank National Park Centre, as well as a number of other sources.

The Ring Ouzel: a view from the North York Moors - advertisement.

We are extremely grateful for all the support and encouragement we have received from members of the National Park staff throughout the study.

Creative writing

A poem from the North York Moors

What is the sky?

Everchanging and expressive,
space and heaven combined.
Infinite and important,
vast desert on high.

Mother Nature flaunting her power,
April showers, hurricanes and storms.
Summoning angry clouds, heavy with rain,
Later filled with light, warming your bones.

Blustery winds and excitable gusts,
fresh air fills and cleanses the lungs.
Billowing clouds, creating beams and rays,
dappled across the undulating land.

Everchanging season casting shifting light.
Rainbows, shooting stars and Aurora Borealis
flashing colours over the great canvas.
Heaven’s glory or natural phenomenon?

Streaked with man’s machines, airplane trails,
aerials, satellites and drones.
Great machines can’t compare
nothing more than flecks on this dome.

Sunrises and sunsets marking our days,
celebrating with glorious colours.
Ink-washed turning to boundless jet black,
encrusted with the finest jewels ready to wish upon.

Westerdale Skyscape. Copyright Christopher Watt, NYMNPA.

Sweetening the land

Ellie Leary – Monuments for the Future Project Officer

Not all of the archaeology within the North York Moors is as ancient and enigmatic as the standing stones or rock art (see previous posts). Once a ubiquitous presence within the landscape, you can still stumble across the remains of a more industrial feature – lime kilns. These structures were part of an industry that has shaped and changed the landscape of the area from the extraction of the limestone from quarries to its end use as a building material and soil improver.

Over 400 lime kiln sites are recorded within the National Park’s Historic Environment Record, with the evidence coming mainly from historic maps, but also earthworks and standing remains. Only three of these kilns have the benefit of protected status as Scheduled Monuments, and in all cases they are included as part of a wider monument rather than in their own right. Another three have protected status as Grade II Listed Buildings.

Grade II Listed Building (1149198) - lime kiln, Hawnby (HER 5946). Copyright NYMNPA.

The use of lime has a long history in Britain dating back to at least the Roman period and over time it has had a wide range of practical uses from forming the base of plasters, mortar and concrete; as lime-wash for waterproofing walls and lightening interiors; in the bleaching of paper and preparing hides for tanning; as a disinfectant; and as a soil improver for agriculture.

During the Roman period it was used particularly for lime-mortar, plaster and lime wash; while during the mediaeval period the need for quantities of lime hugely increased with the construction of large stone-built buildings and bridges. From the 17th century onwards however the main use of lime has been in agriculture, with it being added to soil to improve acidic soils or as a top dressing to pasture to “sweeten” the land.

In most cases in order to turn raw limestone into a useable product it has to be fired in a kiln, creating a process called calcining where calcium carbonate is converted into calcium oxide. This process was both labour and fuel intensive and the trade was known as lime burning – those working at the kilns, were lime burners.

Most of the kilns known of within the North York Moors date to the 18th and 19th centuries, although earlier examples do exist. Excavations at Ayton Castle, for example, revealed a lime kiln dated to the 14th century, which may have produced lime mortar and cement for the construction of the castle’s tower house, the ruins of which still stand.  (This is one of the three kiln sites included within a wider Scheduled Monument – see above).

The earliest kilns were simple clamp kilns which consisted of a circular or rectangular hollow within which the limestone and fuel were layered, covered with clay or turf, and left to burn for a few days. Often clamp kilns leave little obvious trace, however the remaining protected kiln sites in this area (as mentioned above) include two clamp kilns built into the bank of a scheduled prehistoric cross dyke and another cut into the edge of a scheduled Bronze Age barrow – the actual kilns are all thought to be 18th or 19th century in date. Their remains can be seen as horse shoe shaped mounds of earth and stone rubble.

As the demand for lime increased kilns became more substantial in size although the transformation process remained the same. Kilns were generally circular or square stone structures, about 3m in height, with a bowl lined with sandstone or firebricks and at least one draw hole located at the bottom of the kiln. As the contents burnt through the lime was extracted through the draw holes at the bottom. Additional layers of stone and fuel could be added to the top if necessary, otherwise one-off firings were carried out as needed. A good example of this kind of kiln can be found at Old Byland where the remains of four lime kilns stand next to a road (see image below). They are located on the edge of a quarry to the south west of the village and some parts survive to 5m in height, with two of the kilns having the roof and flue surviving.

Old Byland roadside lime kilns (HER 2680). Copyright NYMNPA.

The end product removed from a kiln was called ‘lump lime’, ‘burnt lime’ or ‘quicklime’ and in order to convert this for use it has to be ‘slaked’ – a process involving adding water to cause a reaction which produces heat and steam. By then adding enough water, putty is produced, which, mixed with sand, produces a mortar. Over time this reverts back to calcium carbonate and hardens.  When used in agriculture the ‘lump lime’ was left in heaps, covered in earth and left to slake, eventually creating a powder that could be ploughed into the soil. Other methods were used too, including leaving the lime uncovered and occasionally turning to produce the same result.  ‘Lump lime’ is a volatile material and there were inherent dangers if it started to ‘slake’, producing heat, before it arrived at the final destination.  By the late 19th century, hydration plants were introduced that could grind the lime, sprinkle it with water, dry it and then bag it for transporting.

The location of kilns largely depends on the final use for the ‘quicklime’, so that if it were needed for building construction the kilns would most likely be located close to the building site. They could then either be dismantled and moved or left to decay once they were no longer needed.

Field kilns were sometimes built by farmers and land owning estates from the 17th century. Smaller kilns would have been built by farmers for occasional use to improve their land but estates often built larger kilns to serve the whole estate and wider area, providing a profitable source of income.

Another common location for kilns was close to or within limestone quarries. Many of these quarries are still obvious on the ground now as large excavated pits; historic mapping helps to identify the full extent of the quarries and the location of kilns. The 1893 Ordnance Survey map (below) shows Sour Ley Quarry near Helmsley with up to 20 lime kilns within the quarry.

Extract from 1:2,500 Ordnance Survey Map 1893

Easy access to transportation was also another consideration for the location – for fuel to be brought in and for the final product to taken away for sale.  Colonel Sir Joshua Crompton, 19th century owner of the Kepwick Estate on the western edge of the North York Moors, built a railway line in the early 1820s which carried limestone from a quarry on Kepwick Moor down to the lime kilns and stone yard to the west. Fuel for the kilns could be easily brought in and the final product taken away on the Thirsk to Yarm turnpike road (now the A19). With a very steep incline up to the quarry the railway used gravity; as the full wagons were sent down slope they pulled the empty ones up towards the quarry, whilst horses pulled the wagons along the flat plain to the west. The quarry and the start of the now dismantled railway line lie with the National Park boundary and the lime kilns themselves are a short distance outside the boundary and are protected as a Scheduled Monument.

Lime kiln north of Sinnington (HER 4981). Copyright NYMNPA.

As the demand for quicklime grew the process became industrialised, with new kilns designed with efficiency in mind as well as a higher quality lime product. As a result most of these smaller local kilns were abandoned by the 20th century, with some being dismantled and others left to decay, remaining in the landscape as a reminder of this chapter of industry.

To keep up to date with the latest National Park response to Covid-19 – see here.