Time-travelling by train – Carlisle to Newcastle part 2

We got as far as Brampton station last time. We have changed bedrock from the red Triassic sandstones of the west to 335 to 310 million year old Carboniferous strata – a repeating mix of layers of sandstone, shale, limestone and coal. A product of different past environments when the tectonic plate we were part of was on the Equator.  

Back then the land and sea kept changing places. Shallow coral seas produced the limestones, when sea level fell the environment became brackish coastal muddy lagoons – laying down the shales, which were then covered by sand from large rivers – the sandstones, and in turn they were covered by vegetation and swamps – ultimately decaying and compacting to form coal seams.  

That repeating sequence of rocks – initially with more marine deposits like limestone and as we get closer to Newcastle – more land deposits like sand, mud and coal – is the story of the Carboniferous. Not that we will see much of it directly, this rail journey takes us through a landscape who’s shape and sediments owes most to that last glaciation, its melting and the action of rivers and gravity since. 

Transcript

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Series 5, Episode 3. Time Travelling by Train. Carlisle to Newcastle Part 2 We got as far as Brampton Station last time. We've changed the bedrock from the red Trassic sandstones of the West to 335 to 310 million year old Carboniferous strata. A repeating mix of layers of sandstone, shale, limestone and coal, a product of different past environments when the tectonic plate we were part of was on the equator. Back then the land and the sea kept changing places. Shallow coral seas produced the limestones. When sea level fell the environment became brackish coastal muddy lagoons, laying down those shales, which were then covered by sand from large rivers that produced the sandstones, and in turn that sand was covered by vegetation and swamps. Ultimately that decayed and compacted to form coal seams. That repeating sequence of rocks, initially with more marine deposits like limestone, and as we get closer to Newcastle, more land deposits like sand, mud and coal, is the story of the Carboniferous in the north. Not that we're going to see much of it directly. This rail journey takes us through a landscape whose shapes and sediments owes most to that last glaciation, its melting and the action of rivers and gravity since. But time to move the train along. I didn't say it, but this is a northern rail service these days, using two little carriage diesel units called sprinters. There's usually plenty of seats by the windows to take in the scenery, unless of course you're travelling on a Newcastle United match day or on the last train home from the Toon on a Saturday eve. This section between Brampton and Gilsland is mostly one of humps and hollows, long hills called rigs, and boggy troughs, and a kilometre or so to the north you get glimpses of the River Earthing and sometimes its steep cliffs. Those humps and hollows are hard to appreciate when you're amongst them, but they make more sense when you look at them from far above, preferably when the sunlight is low and the shadows are long. Satellite photographs or lidar images are perfect for doing this. LIDAR is a method of using laser light from a plane or a satellite to measure the height of the ground very precisely, to a few centimetres, and then using mapping software to create a map of that, like a coloured contour map. Anyway, the landscape around here looks like a set of east-west trending long humpbacks. These are drumlins, created by ice sheets depositing and shaping and streamlining the clay, silt, sand and gravel that's beneath them. The topography is called basket of eggs, which is exactly what they look like from above, but they are big eggs, maybe 300 meters wide and more than a kilometre long. These drumlins are one of the early chapters in the glaciation of this region, when twenty to thirty thousand years ago, around a thousand meters thickness of ice was flowing west to east from the Solway Plain and then along the valley now occupied by the river Tyne. We are still west of today's Tyne, but this ice sheet carved out a valley that stretched this far west, one that predated the current Tyne Valley. More on that in a while, but for now, if you were able to look northwards, you could just about recognise Bird Oswald Roman Fort and the River Earthing River Cliff that collapsed to reveal its Roman cemetery. Further along there's a view of Nether Denton with its little church. It lies on the prehadrianic Roman frontier. That was just a road called the Stane Gate, and dates were around AD seventy eighty. Much further north and west, about forty five kilometres further, if it was a clear day, you might also have picked out a flat topped hill called Burnswalk, site of an Iron Age fort, two temporary Roman camps, and right now the subject of a serious and entrenched debate of whether it was a site of a Roman siege or merely artillery practice. Excavations are taking place this year, so if some new facts surface, we might find out which of these interpretations is correct. We pass Gilsland Station, but we don't stop because it's been closed for decades. There's an active local campaign to change that. I hope it succeeds, because it is actually a railway station that, other than the Newcastle terminus of this line, is pretty much on the line of the wall. Wouldn't that be a great gift to all those people who like to visit the wall but don't have or don't want to use a car? The rail line crossed the wall a hundred metres or so back at Poltcross Burn. If you were sharp eyed, on the north side of the track, you'd have seen some impressive ruins of Poltcross Burn Mile Castle, made of grey brown carboniferous sandstone, of course. The line bends east and then south until Greenhead. There's a large expanse of hummocky glacial sand and gravel to the south. To the north is a large, flat, boggy depression, a peat bog that was once a lake, and occasionally, when it rains a lot, it can still look like a lake. We're about to enter a bit of a gorge just before Green Head. Thurwell Medieval Castle, built entirely of repurposed Hadrian stones, stands above a stream, the Tipalt Burn. From here on in we are in the catchment of the river Tyne, flowing to the North Sea, not the rivers flowing to the west and the Irish Sea. Greenhead, the Tipalt Burn, and this gorge and the nearby A69 Road Bypass are all part of a complicated story about the major changes in drainage and topography of this region. We haven't got all the evidence, just the shape of the land and the drainage pattern and a few boreholes, so we can't be certain about the sequence of events, but here is one interpretation of that history. Before the ice ages, a prototype valley used to extend much further west. It was a valley that was adopted by ice sheets heading east, and especially in the last glaciation 20 to 30,000 years ago. Those ice sheets enlarged and altered the valley and deposited huge amounts of debris in it, sand and gravel and stony clays. Boreholes for the Greenhead Bypass recorded over thirty meters of boulder clay or glacial till. These glacial deposits blocked the former upper course of the river Tyne. Rivers like the Earthen draining west into the Eden took over its previous headwaters. The Tipalt Burn southeast of Greenhead is a very small remnant of the Proto Tyne and the glacial meltwater that used to drain east. The river is a misfit. Look at the size of the valley it sits in. A valley our rail line uses as it heads on to Haltwistle, and the confluence of the Tipalt Burn and the South Tyne. The South Tyne's origin is in the Pennines above Alston and Garrigill. That story of ice sheets, meltwater and rivers shouldn't distract me from telling you a few other things about this stretch of the line. Just before Greenhead, we passed south of Gilsland Spa Hotel. It sits at the neck of the Earthing Gorge. It's now in a state of disrepair, and yet this is a place that two hundred years ago accommodated the great and the less good. In the late eighteenth and nineteenth centuries, before going to the seaside became popular, people went to a spa for their health. Two springs near here, one sulphurous, the other iron, in the valley of the river Earthing near Gilsland, attracted locals and visitors alike. Bathhouses once stood beside the river, but all that remains of that early tourist trade today is a rebuilt stone well edifice. It has a modern base and a pipe that dribbles clear water, which sprangs which smells strongly of rotten eggs, and turns white when it's exposed to the air. Two hundred years ago people came to take these waters, drinking a glass or two a day, and immersing themselves in it. According to Augustus Bosing Granville, in his eighteen forty guide to the spars of England, Gilsland's spring water was every bit as good as Harrogat's, but he thought the facilities and the qualities of the local population were very so so. He did, however, appreciate the natural beauty of the earthing gorge, as did Sir Walter Scott. It was here, in seventeen ninety seven at the Popping Stone that Scott is reputed to have successfully proposed to Miss Charlotte Carpenter. Sadly, not everyone respects the natural and literary history of this place. In twenty twenty one, the popping stones were bulldozed aside so that trees could be felled. They have been returned, but the site is not the same. The relevance of geology to these places of pilgrimage? Well, the groundwater that feeds these two springs percolates through carboniferous shales in the cliffs above. The shales contain the minerals iron sulfide and iron sulfate. The water dissolves these and brings them to the surface via a geological fault. The poppin stones have an equally prosaic explanation. They are carboniferous sandstones, rocks that are common in the cliffs nearby, but their rounded shape may owe something to the hand of man as well as river erosion. Stick into groundwater, but not the sort that's beneficial to health. Just after Greenhead you might have noticed too the reed beds and rusty brown waters of a mine water treatment plant, there to deal with the water coming out of the old Blenkinsop drift mine, which only closed in two thousand two and used to mine the little limestone coal seam. We can stay with coal mining in the same coal seam, because the next stop is Holt Whistle, where until 1931 a busy South Tyne Collier employed six hundred men and boys. It's hard to imagine what a disaster that must have been for this small town and how many people must have been forced to find work mining the deeper and more economically viable seams of the southeast Northumberland and Durham coal field. Those same carboniferous rocks used to supply sandstone for buildings, shale for bricks, limestone for agriculture and industrial lime too, and ironstone that used to feed two blast furnaces in this town. They're all gone now. Pause your journey here and take a walk up and down Holt Whistleburn. You can still see the decaying industrial heritage, the evidence for this dependence on geological resources, including Winsil Dolwright from Corfield's Quarry, and not to mention the viaducts that until 1976 used to carry the railway from Alston and the Pennines, a place once rich in minerals like lead, coal, zinc, and fluorite. From Greenhead to Holtwistle the rail line runs across sands and gravels, silts and clays, river alluvium and terraces deposited by the Tipaltburn. From Holtwistle to just west of Hexham, its deposits, it's the deposits of the South Tyne, and then after waters meet, the unified Tyne. The line does its best to hug the flat ground where the river deposits meet the valley sides. The advantages of for minimising gradients and laying a flat track are pretty obvious, but there is a downside. Proximity to river level means increased risk of flooding, erosion of the banks and the track, and landslips from the steep slopes and valley sides. Potential flooding and resilience to that was an issue raised when the line was being submitted for parliamentary approval in the nineteenth century. By the time we reached my home station of Barden Mill, the rivers got very close. Not far from the station there used to be another coal mine working the little limestone coal. More work for another hundred and fifty men and boys. It's quite amazing to think how much bread this little coal seam put on the tables of towns and villages in this valley, and what a role it played in sustaining them all. Just a few hundred yards after leaving Marden Mill, the Tyne is joined by the River Allen. Its waters are the heavy metals brought downstream from the lead mines in the North Pennines, lead, of course, but barium and cadmium also. And the plants along parts of this riverside here at Beltingjam testify to that. There are several species that tolerate these toxins better than other plants. A lot of money has been spent attempting to clean up the rivers that drain from the mining country. But the mines are extensive and they worked for many hundreds of years. Hayden Bridge is the next stop. Once the home of John Martin, the famous late 18th century artist who painted dramatic apocalyptic biblical scenes, many based on his memories of the Tyne and Allen Valley landscapes he grew up in. There used to be another line serve in the lead mines near Allendale here, but it closed in 1950. The Tyne Valley narrows quite a lot at Alawash, and if you look towards the river you can pick out the ribs of the three hundred and thirty million year old Great Limestone, whose southerly sloping beds stretch along the river bed beside us. This is a very rare piece of bedrock on this journey. The valley widens again before we enter Hexham, and the North Tyne has joined us. The floodplain and the river terraces above are extensive. Above us, and forming the sides of the valley to the south, are hummocky deposits of sand and gravel deposited by glacial meltwater. It's free draining land, and one of the reasons Hexham golfers are able to keep playing when other courses are waterlogged. Hexham is a good place to pause, and maybe you'd like to get off this train and head up to this popular market town. It's a short walk. There's an abbey and a Saxon crypt and a jail, all built with grey brown Carboniferous sandstone rubbed from Hadrian's walls, forts, and towns. So it looks like I won't finish this story in two episodes. There will be a third, from Hexham to Newcastle, one that continues the industrial heritage theme and sheds a little more light on how this geological landscape evolved and influenced that heritage.