DAVID SIMPSON investigates, in a hopefully not-too-technical way, how geology has influenced our region’s history and heritage in profound and spectacular ways.

GEOLOGY can sometimes seem a bit of a dry subject but it’s very much a part of our story and in the North East has had a profound impact, shaping our history, heritage and economic development.

The influence upon the landscape and history of North East England is apparent in so many ways. Many of the major themes of our history: industrial; border history; maritime links and several of the region’s most visually spectacular heritage sites have all been shaped by our region’s geological legacy.

Coal

Coal of course is the most obvious geological factor to have shaped our history but how many of us have heard the term ‘Carboniferous Westphalian Rocks’? Very few, I would guess, yet these rocks, more commonly known by geologists in our region as the ‘coal measures’ stretch from the Druridge Bay area of Northumberland to just north of Hartlepool.

From the exploitation of the natural resource of coal within these rocks; wealth, growth and cultural identities were created across our region. Throughout the North East, coal accounted for the emergence of countless colliery villages and paid for the construction of mansions and stately homes for wealthy coal owners. Ports such as Newcastle, Blyth, Shields, Seaham and Sunderland and even ports outside the coalfield like Hartlepool ultimately owed their growth and prosperity to the geological processes that created coal.

The coal deposits in those Westphalian measures spurred on the birth of the railways in our region which had such a profound impact on the emergence of our modern world, especially when coupled with the iron stone deposits of Consett and the Cleveland Hills which helped the region develop into a major centre for steelmaking and engineering.

Coal in our region was of course created from the sediments formed by dead plant matter in the Carboniferous period around 310 million years ago. Those deposits came about when much of what was now England formed a vast marine delta within which plant matter originating in the Caledonian land mass to the north was deposited in our region over vast swathes of time.

The overlaying of new rocks and strata occurred over unimaginable epochs of time under enormous physical pressures and intense heat that compressed the decayed plant matter into coal over millions of years. Later, in some areas subsequent erosion exposed the coal near the surface and here it was first exploited by man. This became particularly important in the vicinity of the Tyne from medieval times where the river became an important means of transporting coal for shipment by sea, gradually creating a significant maritime trade.

Magnesian Limestone Country

The collieries, of which there were once hundreds, have now gone but in recent memory we may think of the colliery landscape of Billy Elliot, a film that was set in east Durham.  This locality, which geologically encompasses Sunderland might be considered as once being the predominant area for coal mining in the North East. In fact this area, where the coal measures stretch far out to sea, was one of the last areas of our region to be exploited for its coal.

Until the 1820s there was some doubt that coal even existed in eastern Durham as this is a landscape with a surface dominated by a very deep layer of Permian rock called Magnesian Limestone (sometimes broadly known as ‘Dolomite’) which overlays the coal to considerable depth.

The Magnesian Limestone was deposited during the hot, Sahara-like climate of the Permian age some 250 million years ago when the area lay on the margins of the shallow ‘Zechstein Sea’ that covered much of what is now Europe. When sea levels began to rise, the desert sands were inundated and overlain with calcium magnesium carbonates which included fossilized coral reefs that together formed the Magnesian Limestone over eons of time. Interestingly, quarrying at Sherburn Hill near Durham has exposed the sands of the original desert that was overlain by the magnesian limestone.

There is a limited outcrop of Magnesian Limestone rock just north of the Tyne, forming the cliffs at Tynemouth but in the main this creamy coloured rock is a south of the Tyne phenomenon, stretching down the coast from South Shields all the way to Hartlepool. It stretches a little way inland too. Take a glance at a satellite map and you will see vast quarries south and east of Durham City which look at first glance like enormous sandpits in the proximity of West Cornforth, Kelloe, Quarrington Hill and Sherburn Hill. On closer inspection they resemble broad moonscapes where trucks and diggers look like tiny toys.

There are signs of this rock being quarried at Marsden near South Shields too and at Fulwell near Sunderland, though the second of these is now greened over and forms a nature reserve. In fact the grasslands associated with this particular rock often attract unusual and sometimes unique fauna and flora, most notably in the form of butterflies. It is one of the prime reasons that East Durham is designated a ‘heritage coast’.

The coastal cliffs along the shore from Tyne to Tees are formed by the rolling magnesian limestone hills of what is called the East Durham Escarpment meeting the sea, forming in world terms, a unique coastal region.

Marsden Rock near South Shields, the coastal cliffs of Blast Beach near Seaham and the Hartlepool headland on which the former medieval port of Old Hartlepool is situated are just some of the coastal features formed by this rock, as are the cliffs along the gorge of the River Wear in Sunderland.

Magnesian limestone has been extensively quarried since medieval times, even giving its name to an early medieval shire called Querningdonshire (Quarringtonshire) near Durham where it was seemingly used in the making of quern stones for grinding corn. In more recent ages it has found use as a flux in the chemical industry of Teesside and is of course most familiarly used in the making of roads beneath the tarmac.

Inland you can clearly see the steeply inclined boundary of the magnesian limestone escarpment where it meets the vale of Durham, most notably forming Houghton Cut near Houghton-le-Spring where a quarry was used in the 19th century as an overspill graveyard during the cholera epidemic of the early nineteenth century.

Near Durham City the villages of Sherburn and Sherburn Hill lie respectively at the foot and top of the magnesian limestone escarpment and at nearby Quarrington Hill ‘the heugh’ near Bowburn on the edge of the escarpment is quite apparent. The top of this hill offered a great vantage point and in 1747 was occupied as a camp site for several weeks by the Duke of Cumberland and his army following his brutal Culloden campaign in Scotland. A century earlier in 1644, a Scottish army under the Earl of Leven had camped here for seven days before heading to Marston Moor.

Before the 1820s most geologists were convinced that there was no coal beneath the deep layer of Magnesian Limestone in eastern Durham though many speculators were keen to take the risk of expensive trial borings in the hope of finding rich rewards. They were unsuccessful until coal was finally discovered at great depth at Hetton in 1822. This marked the beginning of a new coal mining age – the deep mining era – in County Durham which exposed rich and extensive seams of coal and even saw George Stephenson develop his very first railway, the Hetton Railway, at Hetton Colliery.

The mines in this eastern area, that opened over time, would include Easington, Westoe and Monkwearmouth (where the Sunderland football stadium stands today) and were amongst the region’s biggest coal mines in terms of the number of miners they employed.

A glance at the map shows, however, that on the surface at least, the collieries in this area were quite sparsely distributed, reflecting the costs involved in deep mining compared to more westerly areas where there is denser distribution of collieries. Of course deep down the coal seams were extensively worked in east Durham, even extending out to sea.

Iron and lead

In the Pennines to the far west lead mining was of course another big industrial exploit resulting from the abundance of this particular ore. In the nineteenth century Britain was the leading producer of lead and the North Pennines of Durham and Northumberland were the most important lead producing area in the country. Lead mining has left behind important industrial relics such as Killhope Wheel and Rookhope Chimney in Weardale or the Stublick chimney in South Tynedale.

In the Cleveland Hills around Eston, iron ore deposits played an enormous role in the success and growth of Teesside. Middlesbrough, a completely ‘new town’ in the 1830s initially began as a coal port but morphed into the heartland of an iron and steel making region. Items made from Teesside’s iron and steel soon found their way across the world.  A nineteenth century writer remarked:

“The iron of Eston has diffused itself all over the world. It furnishes the railways of the world; it runs by Neapolitan and papal dungeons; it startles the bandit in his haunt in Cicilia; it crosses over the plains of Africa; it stretches over the plains of India. It has crept out of the Cleveland Hills where it has slept since Roman days, and now like a strong and invincible serpent, coils itself around the world.” Sir H.G Reid.

In addition to this legacy Middlesbrough and Darlington would of course become famous for the construction of bridges found across the world from Newcastle to Sydney Harbour.

Geology has contributed in a massive way to our region’s visual and natural heritage too. It has close links to the themes of our earlier history, whether it be Christian sites of international importance or defensive strongholds associated with the Border wars.

Consider the beautiful sandstone bluff around which the River Wear twists and turns to form the ‘dun-holm’ (Durham) or ‘hill island’ on which Durham Cathedral and castle stand in great splendour. They utilise a splendid naturally defended site. In Sir Walter Scott’s words it beautifully forms the “half church of God half castle ‘gainst the Scot”.

The Great Whin Sill

Indeed the region’s most spectacularly dramatic defensive sites owe their beauty to geology and this is no more apparent than in the role played by the Great Whin Sill. This volcanic intrusion was formed by a layer of molten rock that expanded due to crustal tensions caused by tectonic plate movements some 295 million years ago. The molten rock or magma penetrated between layers of softer neighbouring rock. The volcanic rock is exposed in a distinct ribbon-like band across the region as a sloping sill of solid grey-coloured igneous stone.

The igneous stone of the whin sill is some of the toughest stone you will find in the region. It is also called whinstone or ‘Dolerite’ so must not be confused with the very different permeable ‘Dolomite’ that we have already mentioned.

Exclusive to our region, the Great Whin Sill first appears in the south in Teesdale where it forms impressive rocky escarpments such as Cronkley Scar and Falcon Clints but most notably forms waterfalls such as Cauldron Snout, Low Force and of course High Force. Here the River Tees empties its flowing waters with an impressive roar over the distinct whinstone, cutting its way through the layers of softer rocks beneath the dolerite to create a gorge downstream over vast periods of time.

The Great Whin Sill can be traced in a long band north into Weardale (a notable section near Stanhope is called the ‘Little Whin Sill’) and can be traced west of Cross Fell. Further north, where it runs parallel to the Tyne Gap just north of the Tyne, we find the Great Whin Sill put to its most impressive defensive use courtesy of a certain Roman Emperor called Hadrian.

Here the steeply impenetrable slopes of the Great Whin Sill coupled with its proximity to the Tyne gap and the relatively short natural east to west route from the North Sea to Irish Sea provide an obvious site for a line of defence and demarcation. The Great Roman wall that tops the whin sill crags marked the natural northern frontier of one of the greatest empires the world has ever known.

The Great Whin Sill doesn’t end there of course. From the spectacular central sections of Hadrian’s Wall the sill crops up again and again across Northumberland to the north east, contributing to the craggy country in the wilds of ‘the Wannies’ near Sweethope Loughs before finally emerging on the coast near Craster, forming impressive rocky settings for the wonderful medieval edifices of Dunstanburgh Castle and Bamburgh Castle.

Like Hadrian’s Wall these great castles utilise the natural defensive features of the Great Whin Sill with stupendous splendour. Even out to sea, the Great Whin Sill has one last statement to make, forming the rocky weather-beaten outposts of the numerous stubborn little pieces of land called the Farne Islands, while to the north, Lindisfarne Castle nestles grandly on Beblowe crag, a rock of similar igneous foundation.

Of course geology and the landscape features it has formed have not only shaped the region’s heritage but have defined its boundaries too. For nearly a thousand years the great igneous volcanic massif of the Cheviot Hills has formed the northern boundary of our region, separating it from the nation of Scotland, while the carboniferous limestone hills of the Pennines form the boundaries of our region to the west and south west.

Across the Tees to the south east, the Jurassic Cleveland Hills and North York Moors have to some extent isolated the Teesside region from the remainder of Yorkshire, forming yet another natural border for the North East.

It is only in the central south of our region where the Vale of the Tees merges to the south of Darlington with the Vales of Mowbray and York that we have a permanently accessible, if sometimes distant link to the heartlands of England. So geology has defined our region with its permanent legacy and set apart our landscape and heritage. It is not just a part of our story but forms the very letters, margins and structure of our region’s narrative.

Collieries of North East England. Poster Print map (A2 only)