I wrote this a while ago, before we realised that the rocks that lie underneath us in the Forest of Dean are of interest to oil and gas companies. I am still seeking decent and exclusive illustrations… so apologies if it’s a bit text-heavy… it’s a work in progress.
IF we were to condense the history of the planet into a single day, humans would enter it at the very last few seconds. It is largely through our destructive social construct that the planet is experiencing the latest wave of mass species extinctions. Previously you could blame meteorites from space, changes in the Earth’s orbit or the ball of red-hot iron – hotter than the surface of the sun at 1600 degrees Celsius – which spins around in the centre of the planet.
While the Moon tugs at the ocean tides, and atmospheric conditions above our heads cause us to obsess about the weather, beneath our feet a whole lot of action is going on which we are mostly unaware of, unless all of a sudden the fiery mantle spews out molten lava, unseen forces make the Earth shudder and shake, or sinkholes suddenly and unexpectedly open up to swallow houses and cars.
And yet homes, villages and towns have been built from the sandstones or limestones beneath the soil, and the Forest of Dean’s stone, iron and coal industries relied on the natural resources which were formed when the area was a desert, river delta, under a shallow tropical sea. The Forest’s core ranges from 150m to 250m, originally a mountainous plateau caused from a collision with France, Spain, Africa and North America. It is this plateau existence that gave the Forest of Dean such an independent spirit, and the layers of history way before humanity which produced the minerals and fossil fuels that gave populations their livelihoods.
These days, while sinkholes are not so rare, the chances of volcanic eruption or major earthquakes round these parts are pretty slim (there were 25 earthquakes with a sizeable magnitude of 4.5 to 6.1 in Britain during the 20th century) – that is, unless by human endeavour such as hydraulic fracturing, we provoke the planet into violent action. Then again, Iceland and parts of the Mediterranean area, the nearest current ‘hot spots’, are not so very far away. A cloud of volcanic ash not only has the potential to stop flights, as the eruption of Eyjafjallajökull in 2010 did, but such an event can also bring on widespread crop failures, sheep moraine epidemics, and a deterioration in climatic conditions as the acidic fallout from one Icelandic volcano did in the Middle Ages.
Despite being in the grip of an ice age – currently in a temperate phase of it – with sea levels some of the highest for the 800 million years since records can be traced, and rising, and the land sinking and eroding, Britain and Ireland as a whole are protected and anchored by Europe. Like it or not, we are tied to Europe, on the northwest of the continental landmass – the Irish and North Seas and English Channel are superficial, really, as beneath their fairly shallow waters is land. This land extends down 40km to the Earth’s upper mantle, or aethenosphere. It is welded to much deeper and older land, known as cratons, in Finland, Russia and the Ukraine, which is more than double the thickness. Meanwhile, in the middle of the Atlantic, a line that cuts through the middle of Iceland and continues down to the edge of the Caribbean, land beneath the ocean is being ripped apart by a rift as you read this. Chunks of land are forced to plummet down towards the Earth’s core, to be eaten up by fire as they drop thousands of kilometres towards the centre. And down in the Mediterranean, Africa is very gradually consuming the sea and getting ever closer to Spain and Italy. Meanwhile the whole of Eurasia is shifting eastwards, with North America getting crushed by both sides.
Continental crust (land) and the thinner and more brittle and condensed oceanic crust (about 10km beneath oceans) are carried around the planet at a speed of between five and 50 centimetres per year, many scientists believe, on tectonic plates by means of heat convection which emanates ultimately from that ball of nickel and iron, the Earth’s core. Sometimes the two plates – if the edges are continental crust – dock neatly without any tumult, but most times they either strike and slip against each other or one crust is pushed under another. Oceanic crust is generally crushed or slides under land, while continent-to-continent collisions produce mountain ranges on one side, and canyons and basins on the other.
The collisions often reignite faults, or cracks, which were originally formed when smaller bits of land were joined together. This is how the Severn Vale came to be, and May Hill and the Malverns. The contrast in scenery is apparent now whether west of east of May Hill, but would have been far more dramatic 280 million years ago.
Because of the incredibly slow pace of continental drift – or wanderings – mountains don’t spring up overnight. They take millions, sometimes tens of millions of years, to form, and even as they form they begin to erode – some quicker than others, depending on the rock and climatic conditions. But as sure as day turns to night and back again, a cycle lasting roughly 500 million years sees continents come together to form one supercontinent, and then disperse. The land that became the Forest of Dean went from being low-lying to raised up to its fullest extent at the edge of a mountain range that extends west across Wales when Pangaea (meaning ‘all land’) was formed. Now midway through the supercontinent cycle, it has eroded so only the stumps of the mountain plateau remain.
It happened so long ago that it’s hard to retrieve enough paleomagnetic or paleogeographic data to determine where on the planet the land that became the Forest of Dean was originally formed, by magma from the Earth’s mantle (right now, unbeknownst to us, the Earth could be adding extra layers 40km below us), but it’s likely to have been in the middle of an ocean, close to the South Pole. Since then we have mostly been on a north-easterly trajectory. In another 250 million years the land will be close to the North Pole, on the edge of the next supercontinent. It’s likely that the temperature will be about the same as now, perhaps even warmer, as the ice age will be long over.
The last glacial maximum – as the latest freezing phase of this ice age is known as – ended about 11,000 years ago. The resulting melting glaciers (although the ice sheet didn’t cover the Dean, it came close, and the land would have been severely affected by the rapid melting of mile-thick ice) scalped and washed away all traces of 300 million years of earth history in the Dean and uplifted the land again. Scotland is still rising after the weight of the ice was lifted off its back (while we and the south of England are sinking a millimetre or so per year). But even though the more recent layers were stripped away, the stories represented by the remaining layers can still be pieced together.
Where to start? Right at the beginning…
13,798,000,000,000 years ago [13.798ga]
Birth of the universe
I DON’T know about you, but the hardest thing to get my head around is that something – and eventually everything – came from nothing. Scientist Alan Guth, the proponent of the cosmic inflationary theory, calls that void from which the universe which we know of emerged as a false vacuum: false in that the vacuum was temporary, and vacuum meaning a state of the lowest possible energy density (but crucially above zero).
So, according to Guth’s theory, at first, there was nothing. Or seemingly nothing. The apparent nothingness decayed because it contained a miniscule amount of energy. This energy converged at one point, producing what it now near universally accepted as the Big Bang. This energy, or matter, condensed in one spot less than a billionth the size of a light particle, or proton. This bubble, before expanding, achieved a near-uniform state. This meant that as it rapidly expanded – as it continues to do so today – it does so in equal measure in all directions. But if it was completely uniform, the building blocks of atoms would never have come together to become atoms and matter wouldn’t matter!
This collation of matter was so freakishly hot and dense it turned gravity on its head, so instead of objects being attracted by each other, as our Earth and Moon are, they found each other repulsive and inflated, and 13.798 billion years ago…
BANG-KER-BLAM!!! A colossal explosion gave birth to the universe.
This fireball is invisible, as there are not yet light particles to illuminate the universe and make it transparent – protons evolved 380,000 years later. Yet this Big Bang is still detectable – one per cent of the static, or snow, which fills the screen when tellies are detuned has come directly from the Big Bang’s afterglow.
In the space of 0.0000000000000000000000000000000000001 of a second, or one trillionth of one trillionth of a second, the universe doubles in size, and in another 10-37 of a second doubles again, and so on, until the process slows down and a hot cosmic soup fills space.
As the universe continued to inflate, it became cool enough to coagulate into stars and galaxies. Gravity became an attractive force and dragged into position the alignments we see in our night skies today. Except we would have to wait billions of years before we have a planet to see them from.
Our universe kept expanding, slowing down for a while, then speeding up in the last few billion years.
Although we can now measure the whole of our universe, we only see less than one-twentieth of the universe’s matter. We can only detect the remaining so-called dark matter because of gravitational relationships. The unfathomable force that is currently causing the universe to expand by 73km per second in all directions is known as dark energy.
It’s unlikely – the scientists behind the ‘multiverse’ or ‘bubble universe’ theory and inflationary theory maintain – that our bubble will collide with another universe. And hopefully our bubble won’t burst any time soon.
4,550,000,000 years ago [4.55ga]
Birth of the Earth
Eon: Hadean (4550-4000ma) Precambrian-Archean (4000-2500ma)
By now the Milky Way is a spiral galaxy, a giant web of matter held in place by gravity. But parts of the web are prone to collapse, and this is how our solar system forms. A pile of objects end up in a heap.
Most of the matter forms the Sun, while the rest whirl around it – a disc of dust, hot metals and gases spins around for 100,000 years or so, gradually accumulating mass. A solar wind then blows the condensed rocky and gaseous spheres away and planets and asteroids find their own orbital grooves.
Until recently, the prevailing belief was that the sky and all it contains – stars, sun, moon, thunder, lightening, clouds, rain – was a solid firmament with no beginning nor end. This was the hypothesis in the Bible’s opening book Genesis, compiled during the iron age about 2,700 years ago. Within a thousand or so years Christianity, Islam and other single-deity religions worldwide held that everything was built by one creator.
In 1225, English theologian and later Bishop of Lincoln and Archbishop of Leicester, Robert Grosseteste, envisaged that the Universe was created from an explosion. He theorised that matter crystallised to form stars and planets which nested around Earth. Another four centuries passed before Isaac Newton proposed gravity (in 1687), and it it wasn’t until 1916 that Einstein computed that E equals MC-square, his theory of general relativity.
Science is also tracing the history of the Earth, dating its rocks, lifeforms, DNA, and peeling back some of the layers of human history too. But we don’t know what goes on behind closed doors right now in 2016 CE (common era) at parliament, in corporate offices and in our next door neighbour’s house, never mind who shot JFK or whether Robin Hood was based on a real person, if King Arthur was a King or a self-aggrandised warlord, and whether Alfred or Cnut were so Great. We still know little of what life is like in the past centuries, beyond the often self-perpetuating, myth-making world of kings and queens (the earliest Gaelic text, for instance, is a list of kings).
While history has generally been written by privileged people with their own perception or agenda – or those often second-guessing God, the Pope, their king, bishop, editor or media magnate – advancements in science are throwing up wholly new versions, confounding the old stories, showing that random craziness, things colliding with each other, and a combination of improbabilities have more of a part to play than destiny or pre-ordained order or hierarchy.
The embryonic Earth, with its core of iron, is about 80 per cent the size it will reach when an object the size of Mars smashes into it – the debris, a mixture of Earth rock and the asteroid’s – crystallises into the Moon. It’s thanks to the Moon, its size and proximity, that the Earth remains relatively stable and develops an atmosphere. Until the moon locks into its current position and orbit, conditions on Earth are chaotic – tumultuous tides and fiery chasms dominate. But it doesn’t take too long, less than a billion years, before conditions are stable enough for the Earth to develop a magnetic field, its core to sink to the centre, and its surface to cool enough to form a skin, or crust. Not that it will ever become totally stable.
Scientists now think that water was present on the Earth from the beginning – now that a mass of water has been discovered beneath the Earth’s crust, within its mantle. Then again, may be thanks to Mars or some passing asteroid that water reached Earth and eventually also the first life-forms – micro-organisms. Mars was smaller than Earth so cooled much more rapidly, meaning life only had half-a-billion years to develop before everything froze.
The sun still has an estimated 5 billion years left to shine. Andromeda could wipe us out in a collision one billion years prior to that. The Earth, and the Forest of Dean within it, won’t last nearly as long… so let’s enjoy them while we can.
1,600,000,000 years ago [1.6ga]
First foundation rock
Eon: Precambrian-Archean (4000-2500ma) Precambrian-Protoerozoic (2500-541ma) Phanerozoic (540ma-now)
Era: Paleoproterozoic (2500-1600ma) Mesoproterozoic (1600-1000ma) Neoproterozoic (1000–541ma)
Period: Statherian (1800-1600ma) Calymmian(1600-1400ma) Ectasian (1400–1200ma)
Today (2015), the Forest of Dean is a plateau between two rivers, situated on the island of Britain, rising up on a tectonic plate that stretches westward to volcanic Iceland and the Mid-Atlantic Rift’s submerged canyons and mountains, and eastwards to cover most of Siberia and down to the Philippines. This continent came together and in its current place on the globe less than 30 million years ago – Iceland was only formed from a volcanic plume 16 million years ago (or 16ma), and the tiny island of Lundy in the Bristol Channel, about 50ma. At the same rate our fingernails grow, every year this great mass moves a few centimetres to the east, and tilts downwards to the east as well. It collides in slow-motion and is thrust downwards in places by other jarring continental tectonic plates, and thinner ocean crust plates. Eventually all land masses are likely to collide a form a single land mass, before rifting causes land to break apart and form other interesting new shapes, all driven by the moon’s pull.
In a similar way that boiled milk cools enough to form a layer of skin, the Earth cooled down enough by the time it was one billion years old to develop a stable skin. That skin, or crust, or lithosphere, is now 40km thick (and twice as thick in some other parts of the world). It is a constantly evolving skin, added to from below, and occasionally magma shooting through cracks, or faults, to erupt above-ground as lava.
By 1.6 billion years ago, only a fraction of the Earth’s land mass today has been formed as barren land. Out in the ocean somewhere between the more ancient land – or cratons – of Amazonia (Brazil) and West Africa, the basement, on which the inner Forest of Dean perches close to its edge, is formed from magma plumes rising from deep within the Earth’s mantle, emanating from its raging hot core (which is hotter than the surface of the Sun).
This triangle-shaped crystalline rock mass is formed in the Southern Hemisphere at 60-degrees South, not far from the South Pole. This platform or floor is known as the Wrekin Terrane: what will eventually become May Hill is situated right on its edge. The land extends as far west as Tenby. It’s hard to work out how far south because the ripples caused by a continental collision – Africa meeting Europe – destroyed the evidence between 300 and 280 million years ago.
The Earth is a little different: there are about 450 days in a year, and each day lasts for 20 hours – the moon pulling heavier on the Earth. Microbial mats and stromatolite domes formed by photosynthesising algae are the main signs of life in the water – the land is barren, though there may be microbes present helping the rocks form. Under shallow seas sand, mud and silt gradually consolidates into sandstone. The ozone layer has just been formed, and average temperatures are about -3C (29.6F).
Sexual reproduction is a thing of the future… and so is oxygen (this arrives in the atmosphere about 100 million years later, along with eukaryotes – the basic cell type found in almost all life forms).
The Cymru terrane, eventually bumping up alongside and flanking the Wrekin terrane to the west, formed a little later, 1,350 million years ago – at about the same time as the Fenland terrane which extends from the East Midlands to East Anglia. In between the Wrekin and Fenland terranes, the Charnwood terrane, which includes land that will host Newnham, Huntley, Newent, Gloucester, the Cotswolds and extends east as far as London and Belgium, formed much later – 900 million years ago.
More than 650 million years ago, these chunks of England and Wales, together with chunks of Belgium, the Netherlands, Germany, and Ireland, may have been loosely welded together by means of a volcanic arc – in a similar way to which the Caribbean islands and Indonesia were formed much later on. It’s a matter of conjecture whether this embryonic landmass joined on to the mainland of what is now Liberia, West Africa, or to what is now Tocantins, a province in central Amazonian Brazil. Fragments of rock from deep in the basement only come to the surface carried on lava flows, and the tiny amount of evidence matches one or the other.
Between 640 and 570ma, a more extensive phase of arc volcanism took place, which soldered the pieces together. However, the faults – the cracks – between the blocks of land remained, making them susceptible to rupturing, or deformation, should the mass be pressurised by another landmass squeezing up alongside it.
At this stage in the Earth’s history, it’s difficult to trace the wanderings of land masses. There is a roughly 500-million-year cycle where land comes together in supercontinents and then disperses, and the basement miles below the Forest of Dean (west of May Hill and Newnham) may have begun as an extension of the Nuna supercontinent, while the pieces could have come together as part of the formation of Rodinia (1,100-750ma), and again, fully sealed, for the supercontinent of Pannotia (600-541ma).
Where are we now on the supercontinental cycle? About halfway through – now our land is annexed to cratons – the most stable, deepest land masses – in the Ukraine and Finland, and the nearest action is in the Mediterranean, where Africa is pushing northwards, while the Mid-Atlantic Rift is driving a wedge further between Ireland and North America. The Mediterranean Sea will eventually be swallowed by Africa meeting southern Europe, while North America will be wedged on to far-eastern Asia and Siberia. Britain and Ireland will be resting on the North Pole. It may not be as cold as might be imagined – as throughout much of the Earth’s history the poles have been ice-free.
540,000,000 years ago [540ma]
England and Wales unites
Eon: Protoerozoic (2500-541ma) Phanerozoic (540ma-now)
Era: Neoproterozoic (1000–541ma) Paleozoic (541-252.17ma) Mesozoic (252-66ma)
Period: Ediacaran (635–541ma) Cambrian (541–485.4ma) Ordovician (485.4–444.3ma)
Series: Terreneuvian (541–521ma) Series 2 (509ma)
Stage: Fortunian (541–529ma) Stage 2 (529–521ma)
The pieces of crust, or terranes, of England and Wales, after evolving as separate entities in various places, have all slotted into place (sutured) by means of volcanic activity below and above the surface (apart from the Lizard and Start peninsulas of southernmost Cornwall, which is a piece of upturned oceanic crust created about 350ma when the mini-continent of Armorica smashed into Cornwall).
This land, only periodically an island and one which takes many different shapes, including tropical archipelagos, sits on the eastern half of a microcontinent called Avalonia which stretches from New England and Newfoundland to Germany. Five islands which will later form Scotland and the northern half of Ireland are at this stage 4,000 miles across the Iapetus Ocean to the north, off the continent of Laurentia.
Avalonia is formed in the Southern Hemisphere, on the northeastern margin of Gondwana, a continent which straddles the South Pole.
Volcanic arcs culminating about 550ma in the Ardennes, Wales and southern Ireland eventually seal Avalonia as a land platform above the sea, consuming and replacing the crust of the Tornquist Ocean.
Our most distant ancestors, comb jellies, are now hoovering up the oceans’ tiny lifeforms. They have nervous systems and light up when disturbed, as well as voracious appetites and breeding rates. Their contemporaries, sponges, until recently believed to be the ancestor of all animals, in contrast, form passive, friendly cell associations.
Nothing in the world yet possesses a brain. Nothing colonises land.
This process of welding together a “complex mosaic of fault-bounded terranes” began about 700 million years ago. Once formed, Avalonia rifted away from the continent and began wandering northwards, heading towards Laurentia, a continent which contained much of North America and also at least five islands which eventually formed the northern half of Ireland and Scotland.
Until about 600ma, the land spent much of its time developing submerged under a shallow sea studded with volcanic islands. Then the first known mountain-building episode (known as the Cadomian Orogeny) transformed England and Wales into a mountainous region, along with much of north-west Europe (Eastern Avalonia). Within perhaps 100 million years, the volcanoes and mountains were eroded as the land flooded as the sea level rose. Most of central England, including the Forest of Dean, formed a stable block of crust known as a Craton or Microcraton.
475,000,000 years ago [475ma]
Aboard the Midland platform
Eon: Protoerozoic (2500-541ma) Phanerozoic (540ma-now)
Era: Neoproterozoic (1000–541ma) Paleozoic (541-252.17ma) Mesozoic (252-66ma)
Period: Cambrian (541–485.4ma) Ordovician (485.4-444.3ma) Silurian (444.3–419.2ma)
Series: Furongian (497–485.4ma) Lower Ordovician (485.4–470ma) Middle Ordovician (470-458.4ma)
Stage: Tremadocian (485.4–477.7ma) Floian (477.7–470ma) Dapingian (470-467.3ma)
Like a gargantuan cruise ship the extended crust of Avalonia slips its moorings – well, rifted – from Gondwana, and by 440ma it had drifted to about 30 degrees North. The rift creates the Rheic Ocean, with the Iapetus Ocean to the north.
Avalonia was, at less than a snail’s pace but still moving rapidly compared to today’s tectonic plate movements – at my rough but conservative estimate shifting 50cm per year (these days we’re moving at 1 or 2cm per year) – heading towards Laurentia and far-off Scotland and the northern half of Ireland. North and west Wales experienced a fair bit of volcanic turbulence, as did the Lake District from about 510ma.
As Avalonia continues its northward shift, the Wrekin and Charnwood terranes are overlaid with more volcanic and sedimentary rock layers, sealing and stabilising the pair as the Midlands Platform. May Hill to the Malverns are on the western shelf of a rectangular deep sea basin. This trough includes land that will eventually become the Vale of Evesham, the Golden Valley (between Gloucester and Cheltenham), the Severn Vale and Cotswolds. The bulk of the Forest of Dean is low-lying river delta country.
Within 10 million years, the first plants on land will take root, as well as loads of plankton in the sea, vital starting posts in the future food chain.
Roughly 455 million years ago, Baltica – including Scandinavia, western Russia and Eastern Europe – rotating in an anti-clockwise direction towards Avalonia, while Avalonia has been drifting northeast towards Baltica, collided with the eastern end of Avalonia. This closing of the Tornquist Ocean between the two continents coincided with a sudden ice age, where sea levels dropped 100m, wiping out 85 per cent of species. A line which runs beneath the North Sea, Denmark, north Germany and Poland marks the ocean closure (suture).
The melting of the glaciers caused a rise in sea levels until they were at the level they were today, and much of Avalonia was plunged under deep water. The oldest rocks to outcrop, at May Hill, date from a later time when the sea had become much shallower, and the coast was not far to the east. The slightly younger rocks surrounding the top of May Hill are rich in coral reef fossils.
[Fossil found of an articulate brachiopod – a marine shellfish which built reefs – at Glasshouse, near May Hill, in Woolhope Limestone formation, dating from the Sheinwoodian Age (Silurian Period) (426.2 – 428.2 million years ago) when May Hill (pictured, centre) – then a flat continental shelf – was covered by shallow sea, close to the coast (top illustration)]
By 425ma the combined Avalonia and Baltica have locked horns with Laurentia. The docking took 30 million years of slipping, striking and sliding, by which time the north of Ireland joined the south, Scotland joined England, and the Appalachian mountains formed as part of a mighty chain which continued across Scotland and Norway. Volcanos erupted where the Mendips now stand in Somerset.
By now, the Forest of Dean, on the Midland platform (stretching from Tenby to London, and south to Bristol, and just south of today’s M4 corridor), was above the water. Across the sea to the south was Pretannia, another island (now south Somerset and Devon). Mid-west Wales remained a basin filled with a deep sea. There is still some conjecture about whether mountains were formed further south. Those which did formed at north-eastern angles. Could the fault-line which later became the Severn vale, and the Clanna anticline, the slope of upfolded rocks (as opposed to the down-folded rocks, or syncline, of the Dean) that leads from Tidenham up above Woolaston and Aylburton, pushed up the southern edge of the Forest of Dean and perhaps also uplifted the land to the southeast of Lydney (where Naas House and Fairtide rock now stands)? If so, that might explain why older rocks remain on the surface directly to the east of Lydney Docks.
[East of Lydney Harbour, remnants of the oldest remaining hills, now the southern frame of the Forest of Dean?]
[Eastern section of the Clanna Anticline in the foreground, facing south – this flank stretching from Tidenham to Lydney Park may have been formed during the continental collision to the north, which saw Scotland joining England and Wales and the Avalonia subcontinent merging with Scandinavia and North America… was this upland area once part of the Appalachian mountain chain?]
398,000,000 years ago [398ma]
Eon: Protoerozoic (2500-541ma) Phanerozoic (540ma-now)
Era: Neoproterozoic (1000–541ma) Paleozoic (541-252.17ma) Mesozoic (252-66ma)
Period: Silurian (444.3-419.2) Devonian (419.2-358.9ma) Carboniferous (358.9–298.9ma)
Series: Pridoli (423–419.2ma) Lower Devonian (419.2–393.3ma) Middle Devonian (393.3–382.7ma)
Stage: Pragian (410.8–407.6ma) Emsian (407.6–393.3ma) Eifelian (393.3–387.7ma)
We’re at 20 degrees south on the globe, the climate is warm – average Earth temperatures are more than 6C higher than in 2014. Sea levels have dropped and the Forest of Dean area is a river delta, plants which have evolved from algae not more than a few inches tall are growing on the muddy banks. Fish are everywhere.
[Top: 400-360 million years ago, most of the Forest of Dean was on a semi-arid muddy plain crisscrossed with rivers, with uplands (the Wales-London-Brabant High) rising to the north of the Dean in an unbroken line from western Eire to Belgium, culminating at their southerly point around Howle Hill, Hope Mansell and Puddlebrook, these hills were possibly part of an uplift occurring at the same time as the Pennines, Scottish and Cambrian mountains (Caledonian orogeny). 2nd from top: The remnants of these once-great mountains, viewed from the northeast side of Howle Hill, surround the Hope Mansell Dome, once a hill with the shape of May Hill, now almost flattened by water and mud erosion. 3rd from top: Ross-on-Wye (its name thought to derive from ‘Rose Town’) is built on and from red sandstone. 4th from top: a wet period about 390 million years ago transported quartz conglomerate boulders, which now form a necklace around Forest scree slopes, also known as ‘pudding stone’. 2nd from bottom: Tintern Abbey was built with Tintern sandstone, which dates from 375 million years ago and outcrops on slopes and valleys beneath eroded local older sandstone hills, especially either side of the lower Wye valley. Bottom: The area may have looked like this]
The Midland Platform, and Wales, now combined as the Wales-London-Brabant High, south to a line stretching from Ireland to Germany via the Bristol Channel, is now a vast muddy plain which verges from desert to river swamp deltas. Parts of it, including Herefordshire, form a vast arid upland desert, with the oxidised sand, brownstone, still visible to the north of the Forest and around Lydbrook and on either side of the Wye Valley, blown by desert winds to rest and consolidate into iron-rich sandstone. The debris comes from mountains to the north, especially in Powys and Shropshire. The Devonian period is also known as “the age of fishes” but it’s thought life was mostly if not entirely absent in the Forest of Dean during this period, as the several sandstones do not contain organic matter.
Today, the soils of Herefordshire and the river turns red after heavy rainfall, as fragmented ironstones, or brownstones, remain on the surface. About 390ma, flash floods transported great boulders known as jackstone, puddingstone and officially quartz conglomerate to low land and river beds. These incredibly resistant rocks – thanks to their imbedded quartz – form bracelet trails through the Wye Valley and parts of the Dean, some close to or in the river. Others have since been lifted up, as high up as Staunton – possibly as recently as after the most recent big freeze, 10,000 or so years ago.
Laurentia, Baltica and Eastern Avalonia went through a protracted dodgem-bumpfest of collisions lasting 150 million years, before finally amalgamating, sometimes necessitating earth movements and volcanic eruptions, as well as vast quantities of sand from eroding mountains tumbling southward.
The final act of the so-called Caledonian orogeny (mountain-building episode) saw the Iapetus Ocean plate forced under and through the crust of the continents between Scotland and Angelsey, and this major upheaval caused the land to buckle and warp. The Appalachian, Scandinavian and Grampian mountains formed a huge Himalayan-sized chain, which began eroding as it was thrust up, the debris covering the lowlands with masses of red iron-oxided sand and mud.
Britain and Ireland (aside from the Lizard and Start in Cornwall) were now composite structures. They formed the southeastern flank of the mighty old red sandstone continent.
The last stage of southern Britain closing the gap with Laurentia folded more rocks, and ‘deformed’ the land, still evident in the Lake District, Scotland and North Wales, but it probably happened further south too. It continued to build mountain ridges and plateaux.
Perhaps the land remained a plateau for 10 million years or more, from about 385ma, as a successive layer of purer sandstone was lain down in the Wye Valley from Coppet Hill to Tintern, in the Hope Mansell dome and Lea Bailey, and presumably elsewhere in the Forest of Dean area (now buried under later rock layers) between then and 359ma. The stone is limited to this area, indicating the sediment came from fast-eroding local hills.
350,000,000 years ago [350ma]
The first Foresters?
Eon: Protoerozoic (2500-541ma) Phanerozoic (540ma-now)
Era: Neoproterozoic (1000–541ma) Paleozoic (541-252.17ma) Mesozoic (252-66ma)
Period: Devonian (419.2-358.9ma) Carboniferous (358.9–298.9ma) Permian (298.9-252.17ma)
Series: Upper Devonian (382.7–358.9ma) Mississippian (358.9–323.2ma) Pennsylvanian (323.2–298.9ma)
Stage: Fammenian (372.2–358.9ma) Tournasian (358.9–346.7ma) Visean (346.7–330.9ma)
Perhaps its a little facetious to make a claim for the first Forest dwellers before the area was even wooded – but I can’t resist handing the honour to the crinoids: still resident in fossil form (with 600 different living, evolved versions of the echinoderm species in seas and oceans elsewhere in the world – 5,000 species are now extinct).
Generations of the gregarious, huge population of tree-like aquatic animals, stood rooted to the spot for millions of years; as each one died its skeleton contributed to the rocks that now lie beneath the soils west of Bream – a rich agricultural landscape farmed since neolithic times, which currently faces utter desecration from a massive quarrying corporation.
[Top: crinoid segments fossilised in limestone. Middle: live crinoids. Bottom: guide to a crinoid]
Crinoids live together in crowded populations, each attached to shallow seabeds by a stalk and tubular feet. Each has more than five arms which they use to filter food (plankton), and an anus next to their mouth. Their main visitors are snails, which feed on their waste products. Males and females release sperm and eggs in surrounding sea water, which together produce larvae. Females have been known to brood their offspring with their arms until they are old enough to grow stalks and spend the rest of their lives hanging out before their stalk segments eventually form disc imprints in the consolidated rock of their ancestral brethren.
So how did these ‘first foresters’ get here?
As Laurussia (including Britain and Ireland) heads towards the gigantic Africa-South America-Australia conglomerate continent Gondwana, it causes the sea levels to steadily rise so much of the Forest of Dean, South Wales, Bristol and Somerset, and Ireland, lies on a shelf under the warm, shallow, clear Euramerica Seaway – this marine band which encompasses most of Ireland and Britain and stretches to Belgium and across northern Europe. We’re now almost on the Equator (four degrees south) – the environment’s like the Bahamas, with no change in seasons and shellfish abound. There are few, if any, rivers flowing into this sea, the mud is made of lime.
From about 354ma the Dinaric crinoidal limestone pavement stretches from just east of Newport and also south towards Bristol and west to form the islands Steep and Flat Holm, forming a broad band across St Briavels and Bream to East Dean, and as far north as Symonds Yat and Ruardean and reaches thicknesses of 1,500 metres. The coast to the north starts beyond Coppet Hill, at Goodrich, and eastwards to Hope Mansell and Longhope.
While the limestone doesn’t crumble like sandstone, it is porous and weak-acid water dissolves parts of the rock to form subterranean rivers and cave systems – a landscape feature peculiar to limestone, known as karst.
At the same time, there is a massive expansion of four-legged stem tetrapods, proto amphibians, and lizard-like amniotes became the first animals to be born on land. The climate on and near the Equator becomes warmer, while an ice age freezes much of Gondwana further south, and also the Siberia continent to the north of Laurussia.
The sea levels dropped within 25 to 30 million years, and a band of land stretching from Pennsylvania to Germany became a tropical swamp, populated by giant flora and fauna.
The transition and shrinking sea is marked by a series of folded limestone rocks which circle the inner Forest of Dean coalfield and areas to the southwest of it. Perhaps the best way of seeing the sequence is to follow the Soudley Geology Trail from the Dean Heritage Museum.
The youngest in the sequence is the Cromhall Sandstone, a mash-up of limestone and sandstone, which marks the transitionary period when the sea came and went, leaving a very salty and sandy area of swampland, a plain intermittently flooded, and populated by worm-like creatures which imprinted themselves in fossils.
354-352ma Avon Group (mudstone/limestone): outcrops on the hill between Cinderford and Littledean inc Ruffit, Collafield, above Green Bottom, W of Plump Hill, Stenders, N of Wigpool, N of Ruardean, Deep Dean, outer parts of Howle Hill, Bishopswood, Welsh Bicknor, Lower Lydbrook. Eastbach, Symonds Yat Rock, SE of Ganarew, Upper Redbrook, Whitecliff, Clearwell, Bream Avenue, NW of Lydney, plus parts of Stowe, Hewelsfield (and west of Chepstow and Tintern). Comprised mainly of crinoids (a sea animal known as a stone lily which lived in large densities on the sea floor) and shales, average 200ft.
352-344ma Black Rock Limestone (dolostone): adjacent band, inside Avon Group around the coalfield, and in blobs inside Avon Group areas west and southwest of it. Pinkish-grey lower dolomite, average 300ft thick.
344-343ma Gully Oolite (crease limestone) adjacent, inside Black Rock group, narrow band from between Mallards Pike and Bradley Hill, to N of Morse Lane, then W of Joys Green, then Hillersland, Doward, wider on W side, E of Staunton, Scowles, Milkwall, NW of Lydney. Average 100ft thick.
340-339ma Llanelly Formation (Whitehead limestone) – Limestone and Argillaceous Rocks (limestones with a lesser amount of clay minerals) interbedded. Adjacent, inside the band of crease limestone, average 100ft thick.
339-335ma Hunts Bay Oolite Subgroup – Limestone, Ooidal – N of Lydney, W Bream, W of Ellwood.
337-327ma Cromhall Sandstone, aka Drybrook Sandstone – Hangerberry, central Lydbrook, E Morse Lane, Drybrook, Puddlebrook, Wigpool, then adjacent, inside E side of Whitehead limestone to Staplehill (youngest section Edgehills Sandstone). Average thickness, 300ft.
310,000,000 years ago [310ma]
The rise and fall of the coal forest
Eon: Protoerozoic (2500-541ma) Phanerozoic (540ma-now)
Era: Neoproterozoic (1000–541ma) Paleozoic (541-252.17ma) Mesozoic (252-66ma)
Period: Devonian (419.2-358.9ma) Carboniferous (358.9–298.9ma) Permian (298.9-252.17ma)
Series: Mississippian (358.9–323.2ma) Pennsylvanian (323.2–298.9ma) Cisuralian (298.9–272.3ma)
Stage: Bashkirian (323.2–315.2ma) Moscovian (315.2–307ma) Kasimovian (307–303.7ma) Gzhelian (303.7–298.9ma)
A tropical forest straddles the Equatorial band of the continent of Laurussia, rising up from a river delta. The climate conditions are like the Amazonian delta, but the trees very different. The world’s first forest stretches from Pennsylvania to Poland, rising up as the Euramerican Seaway retreats from the area from about 325 million years ago.
Wish you were here… in the proto-Forest of Dean?
A Carboniferous forest featuring Lepidodendron aculeatum (resembling feather dusters on long sticks), Sigillaria scutellata (resembling toilet bowl brushes), Asteroxylon mackiei (at this scale may be mistaken for grass), and ferns. Some Lepidodendron grew as tall as 150 feet.
This tropical paradise would actually be quite frightening for humans. The sky is dark yellow from all the wildfires that erupt and blaze here, there and everywhere, caused by constant electrical storms. There has never been so much oxygen in the atmosphere as there is now, and this means everything grows rapidly and huge. Dragonflies with wings spanning more than six feet, millipedes the size of articulated lorries, ferns 30 metres high and 1.5 metres wide with incredibly thick bark, ginormous spiders… it’s all gone a bit Carboniferous Alice in Wonderland. The oldest-known moss species in the world, Muscites plumatus, from this time has been discovered in fossil form at Puddlebrook Quarry.
But nature’s a bit messed up: the incredibly thick bark protects the plants but is poisonous to many of the vegetarian animals, and so the trees are no good as a food source. Although it’s warm here, the Earth is in the grip of an ice age, to be followed by a rapid period of global warming. The ecosystem is fragile at best. A continuous equatorial belt of humid rainforests is reduced to islands – the Forest of Dean is one of these.
For the first 10 million or so years of the carboniferous forests, they were continuous and the same species of fauna and flora – particularly giant 100-feet-plus-high club mosses called Lycopods, horse tail trees and fern-like plants called Pteridosperms, the latter growing on high mud banks – could be found throughout. But by about 309ma and a few million years earlier elsewhere (the process began from 320ma), some swamps had dried up and become barren. The largest nearby forest then covered the middle of South Wales, from Carmarthenshire to Blaenavon; the Forest of Dean’s extent was almost precisely that of the post-1830s Statutory Forest – 90 square kilometres, with a smaller area (19 square km) of coal forest immediately west of Newent, stretching up to Dymock. South, parts of what became the Bristol Channel south of Chepstow were covered with carboniferous flora, as was an area from north of Bristol to Somerset.
The trees didn’t die in the same way as modern ones do: they rotted on the spot, with anaerobic bacteria converting the oxygen from the plant tissue and releasing it as sulphuretted hydrogen. This toxic gas destroyed life, and also combined with iron to form iron sulphide, a key ingredient of coal. But coal took millions and millions of years to form.
After the bacteria has done its worst, the vegetation is a putrefying jelly-like mass.
The toxic, rotted forests are buried by a succession of landslides and swamp subsidence – the turbulence happens in other forests than the Dean at first, but the environmental chaos starts here around 308ma. There’s a see-saw effect as an area from Wales to Belgium (known as the Wales-Brabant High) rises and rivers drag down vast quantities of sand at a rapid rate, while the sea washes in periodically turning the central Forest area into a lagoon.
Eventually all that was left of the forest was peat, thousands of feet deep – which eventually compressed to become more than 800 metres of sandstones embedded with coal.
This coal and Forest Pennant sandstone would, from 2,000 years ago, make the Forest of Dean a hub of industry. The immediate effect of the climate chaos and landscape upheaval was to pave the way for the domination of dinosaurs. The amphibians’ and floras’ loss proved the reptiles’ gain, as the latter could adapt to the oncoming desert conditions.
There are basically three waves of coal forests resulting from massive burials of sand brought from what is now Herefordshire by rivers. Within them can be found 19 seams:
From 308ma: Trenchard – pinkish-grey quartzite mudstone and sandstone with a few coal seams, up to 300ft thick.
From 307ma: Coleford – a coarse-grained Pennant-type sandstone interbedded with grey and green mudstone, ironstone and coal, featuring the most productive coal seam, the Coleford High Delf, which is up to 5ft thick. The rock is 180m thick in the north, and rises to 300m in the south. Found at Steam Mills, Harrow Hill, Ruardean Hill, Brierley, The Pludds, Edge End, Mile End, Five Acres, Joyford, Berry Hill, Broadwell, Coleford, Coalway, Ellwood, Bream, Whitecroft, Pillowell, Yorkley, W of Ruspidge, and Church Rd, Cinderford.
306-299ma: Cinderford – containing quite thick coal seams, a mix of mudstone, siltstone and sandstone, grey to red, in places containing clay, parts – such as the Serridge Sandstone – wholly sandstone in the north to shales in the south. Again, from 180m in the north to 300m thick to the south. This occupies the centre of the Forest of Dean, including Drybrook, Cinderford, Hawkwell, Cannop, Speech House, Parkend and Moseley Green.
The Newent coal was formed at the same time as the Trenchard and Coleford layers, as was the Severn Coalfield, while coal in Somerset ceased being formed at the same time as in the Dean. In South Wales, Nailsea, Somerset and Bristol, the chaotic landscape collapse which gave the world coal started a few million years earlier – from 311ma – although there is a chance they could have been swept away from the Dean and Newent by earth movements, from the aftermath of a collision with Armorica, aka Cadomia (France, Spain and Germany’s Black Forest), which may have triggered volcanic activity in the Severn area and helped fold limestone rings around the Dean. Aside from the Forest of Dean, only in two tiny areas near Dymock, and a fraction of the much larger coalfield north of Bristol, Nailsea and north Somerset, have the coal measures remained close to the surface.
280,000,000 years ago [280ma]
Pangaea and the plateau of Forest independence
Eon: Protoerozoic (2500-541ma) Phanerozoic (540ma-now)
Era: Neoproterozoic (1000–541ma) Paleozoic (541-252.17ma) Mesozoic (252-66ma)
Period: Carboniferous (358.9–298.9ma) Permian (298.9-252.17ma) Triassic (252.17-201.3ma)
Series: Pennsylvanian (323.2–298.9ma) Cisuralian (298.9–272.3ma) Guadalupian (272.3-259.8ma)
Stage: Asselian (298.9–295.0ma) Sakmarian (295.0–290.1ma) Artinskian (290.1–283.5ma) Kungurian (283.5–272.3ma) Rodian (272.3–268.8ma)
AFRICA and the glaciated continent of Gondwana collides with southern Europe somewhere in the Mediterranean or perhaps further north, producing a ripple effect which eventually creates mountain ranges across central France, Brittany, Cornwall, Devon, Somerset and Wales – and uplifts the basin of the Forest of Dean, making it a plateau fortress with a heart-shaped limestone rim, containing three main north-south rock folds.
The process of the formation of the supercontinent Pangaea forming took almost 200 million years. This final event – or orogeny – sealed the Forest of Dean’s geographical independence, and made it a little country all on its own (the two rivers which frame it, the Severn and Wye, would only take shape between 2 million and a few thousand years ago).
The landscape was transformed from a low-lying swamp to a plateau of Alpine proportions.
The so-called Variscan orogeny which formed a much more extreme version of the landscape we enjoy today, was the culmination of three big tectonic plates converging. So, having already surviving collisions with Baltica, Laurentia and Armorica/Cadomia, the final event was when the gargantuan continent of Gondwana smashed into the accumulated landmasses, including at the south of Spain. While the earlier events may have ‘deformed’ this area, this was the big one that triggered new mountain chains from the Atlas to the Mendips, and also May Hill and the Malverns.
The Malvern fault line, created between 700 and 540 million years ago, when the Wrekin terrane crust and the Charnwood terrane crust soldered together, was reactivated. This caused the eastern Charnwood terrane to slide under the western Wrekin terrane, rising up and folding rock layers westwards of May Hill and the Malverns, and immediately to the east produced the Worcester graben – a dramatic drop of up to 2,500m. (now the Severn, Avon and Leadon Vales). The triangular block of hills around May Hill was shaped by the Blaisdon fault, while the remains of parallel north-south ridges stretch northwards to the amphitheatre-shaped Woolhope Dome in Herefordshire, and westwards as far as the Usk valley.
Rock formed hundreds of millions of years previously was thrown up, including the Malvern Hills, May Hill, Brights Hill, Huntley Hill, Popes Hill, and across what is now the Severn between Blakeney and Newnham to Tortworth. The Blaisdon fault line not only gave the May Hill triangle its shape but bordered a steep red sandstone wall at Longhope. From the south, the Severn axis and Clanna faultline, northwest of Lydney, brought the limestone pavement up on to a high plateau (perhaps not for the first time) which continues to Newport, and southwards to the Avon Gorge near Bristol and to the Mendips. A fault-line running through the Usk valley separates the Forest of Dean and western plateau from the Welsh hills further west, but resulted in a gentler slope than the Malvern line boundary.
To the northwest of the Dean, beyond Howle Hill, a now-dry proto-Wye river valley began to cut through, separating Chase and Penyard Hills from the rest of the plateau. At Coppet Hill the plateau continued across the current Wye, encompassing Little and Great Doward, Ganarew, Buckholt and, south of Monmouth, Penallt, Trellech, Devauden, and west and northwest of Chepstow.
While the eastern, southern and northern edges are easily traced, in many places defining the western edge of the plateau is arguable – at the most generous estimation its foothills stretch as far as the Usk valley. West of this rises the South Wales coalfield, a similar structure to the Dean area but about a dozen times the size. And the Welsh valleys have an often parallel and overlapping history to the Dean, more so than the rest of Gloucestershire and Herefordshire have.
The scenery we enjoy today west of the Malvern Line is the stumps of the mountain range, raised basin and plateau – May Hill the highest point at 295 metres, the eastern boundary ridges of Breakheart Hill – where the incredible forces behind the rock-folding can be witnessed at the Wilderness Quarry, with old red sandstone rocks heaved up to an angle of 60 degrees – the higher Edge Hill, Littledean Ridge, and Allaston Ridge and the Forest of Dean plateau at various points between 150 and 280 metres – perhaps one-tenth of the height they are when formed. River valleys cut through in changing patterns during the next 280 million years. Dean’s landscape in its early days has been compared by geologist William Dreghorn as similar to the Dinaric Alps of Slovenia and the Balkans look now, the interior filled with piles of peat thousands of metres deep. Miners will encounter places where coal seams unexpectedly run out – these ‘wash outs’ are due to the courses of ancient rivers. The landscape eroded at an accelerated pace from the off, the original rugged peaks becoming smooth domes in the first 50 million years after the uplift.
It’s the asymmetry of the central Forest which has made it both a boon for life – plenty of freshwater collects in its basin – and hazardous for industry – the one per cent of the coal measures which contain coal is frequently waterlogged (but at least mines were methane-free).
Now Pangaea was complete, within 30 million years Newent became a sandy lowland bog, while hot desert sands were carried north – by water and in more arid times, wind – from Paris and south Devon to cover Newnham, Broadoak, Elton, Birdwood, Rudford, and Taynton through the basin that will eventually become the Bristol Channel and Severn. This channel is known by geologists as the Budleighensis River. Much of the area would have been dunes, with an inland sea or lake forming at Wesbury-on-Severn.
We are now in the centre of the Pacman-shaped supercontinent of Pangaea (or ‘All Earth’). Most of north and central Europe is covered in a salty sea within a desert basin, beginning at a point not far off the coast from Hull and Grimsby. As we’ve only just left an ice age (though we didn’t feel it, as we were near the Equator), the melting of the ice caps will eventually submerge most or perhaps all of Britain, receding to leave much of it a flat desert with salt pans.
In the uplifted Forest of Dean and the areas to the north and west of it, no new rock layers can be found. Dreghorn noted in the late-1960s: “In its structure the Forest of Dean is a unique region, an interior plateau in the form of an oval-shaped saucer… Plateau areas throughout the world tend to be rather isolated regions in which the inhabitants develop customs and dialects of their own. The Forest is no exception and although its isolation is being broken down by motorways and bus services, the inhabitants still preserve clannish characteristics.”
And yet anyone who has spent enough time in the ‘Forest of Dean syncline’ – preferably nowhere near a TV – will feel remote from the rest of the world. East of the several ridges which frame Mitcheldean and Longhope, by the time you’ve hit the A40 or gone south to the A48, you’ve left this otherworld behind and entered land a few miles or more above the Charnwood terrane, which stretches all the way to London. Those hills in the distance – the Cotswolds – are only about three million years old.
Behind, the Forest of Dean and Welsh hills are almost one hundred times as old. They have spent much of their time under water, as well as weathering desert conditions and sheets of ice down the eras, and moved steadily northwards up the globe.
About 250 million years ago conditions are barren – 96% of all plant, animal and microbe life becomes extinct worldwide (there are numerous theories why, but none have consensus – the most likely is due to lack of oxygen in water, and perhaps lack of water in a vast desert). Ocean reefs and forests are destroyed. Gone are rhinoceros-sized plant-eating mammalian reptiles and sabre-toothed gorgonopsians that preyed on them.
This wipe-out happened over 500,000 years – the most severe of the Earth’s ‘Big Five’ extinction events. The remnants of amphibians and reptiles species evolved into dinosaurs and mammals within 20 million years. One of the earliest mammals, dating from 225ma, was a rat-sized animal found in the Mendips of Somerset.
150,000,000 years ago [150ma]
Eon: Protoerozoic (2500-541ma) Phanerozoic (540ma-now)
Era: Paleozoic (541-252.17ma) Mesozoic (252-66ma) Cenozoic (66ma-now)
Period: Triassic (252.17-201.3ma) Jurassic (201.3–145ma) Cretaceous (145–66ma)
Series: Middle Jurassic (174.1–163.5ma) Upper Jurassic (163.5–145ma) Lower Cretaceous (145–100.5ma)
Stage: Kimmeridgian (157.3–152.1ma) Tithonian (152.1–145ma) Berriasian (145–139.8ma)
THE youngest solid rock layer to be found anywhere in the area covered in this book, known as Blue Lias, is below the plateau, on the edge of the Severn, some east of Sedbury, others east of the Malvern line from Westbury up to Over and Gloucester.
From 208 million years ago, the area that had been raised up by continental collision less than 100 million years earlier was now low-lying and covered in a shallow sea, at roughly the same latitude as southern Spain is in 2015, and a couple of thousand miles further east. Rock fragments found near Bristol indicate we may have been showered with debris from an asteroid crash in Canada.
The Jurassic limestone is rich for fossil-hunting and the far eastern end of Garden Cliff, Westbury beyond the fossil-free but gorgeous red marl at this Severnside rockface, are nirvana for ‘rockers’.
Ammonites, snails, sea cucumbers, sea urchins and worms are everywhere. They, and sharks and rays, are gobbled up by the largest animals in the sea, reptiles such as crocodiles.
By 150ma the sea has retreated but is still at a high level worldwide, Pangaea is no longer in one piece, and a rift has started between Ireland and North America, although both Greenland and Canada are still close and the Atlantic Ocean doesn’t yet exist. There are lots of dinosaurs around: they leave footprints at Barry Island and many other locations… the best evidence of Jurassic life offered locally is the Ichthyosaurus – a six-feet-long marine animal found at Awre embedded in the 170ma-old lias clays. Like mammals, they give birth to live young in the water, tail-first so their babies don’t drown.
The subterranean cave system within the limestone of the Dean and the western plateau (created by water seeping through the newly-formed rock), becomes exposed at the surface following prolonged heavy rainfall.
These hollows, portals into the underworld, are unique to the Forest of Dean and Wye Valley, and are known as scowles (probably derived from an Old Welsh word crowll, meaning a hollow, or the Welsh word ysgil meaning a recess, the hamlet Scowles, near Coleford, is first recorded in 1287 as Scwelle). They are said to have inspired the landscapes in The Hobbit and Lord of the Rings, as the author JRR Tolkien explored them during his time as an archaeologist near Lydney in the 1920s. The classic form (one of three types) appear as deep irregular, linear quarries.
[Scowles marked in brown]
A recent survey has found 694 scowles on limestone outcrops around the edge of the Dean rim, including across the Wye at the Doward. The best known ones are Devil’s Chapel, Puzzle Wood and Stockwood, between Lydney and Coleford, and near Wigpool on the opposite side of the Forest.
Until recently they were believed to be manmade, by primitive miners digging for iron ore. Now there is a general consensus they are a natural phenomenon. As well as iron mines, they have been dwellings and rubbish tips.
Rainfall pushes a slurry of only half-formed coal as well as shales, dripping through the gaps, leaving the iron ore solutions in cracks and crevices nearest the top, and chemical processes fuse the ferric with the calcium and magnesium carbonate cave walls and ceilings. Iron came from the coal measures, the soils and the water which filled the cavities at times when the sea levels drowned the entire area.
The ores include ochre, and a brush ore which required little preparation before smelting. At New Dunn iron mine in Clearwell, a massive churn running down from a hole in the roof was made entirely of brush iron, providing miners with an 18-month-long ready supply.
Scowles develop most often in the crease limestone, and to a lesser extent in Lower Dolomite, Drybrook Limestone and Drybvrook Sandstone. The ochre and ore-bearing scowles, as well as coal and stone, are as essential to the making of the Forest of Dean as trees and topography, in both political and social terms.
Last 150 million years [150ma-1ma]
Recently in deep time
Eon: Phanerozoic (540ma-now)
Era: Mesozoic (252-66ma) Cenozoic (66ma-now)
Period: Jurassic (201.3-145ma)– Cretaceous (145–66ma) Paleogene (66ma–23.3ma) Neogene (23.3–2.58ma) Quaternary (2.58ma-now)
Epoch: Upper Triassic (163.5-145ma) Lower Cretaceous (145.3-100.5ma) Upper Cretaceous (100.5-66ma) Paleocene (66-56ma) Eocene (56-33.9ma) Oligocene (33.9-23.03ma) Miocene (23.03-5.333ma) Pliocene (5.333–2.58ma) Pleistocene (2.58ma–11.7ka) Holocene (11.7ka–now)
Stage: Kimmeridgian (157.3-152.1ma) Tithonian (152.1-145ma) Berrasian (145-139.8ma) Valangian (139.8-132.9ma) Hauterivian (132.9-129.4ma) Barrernian (129.4-125ma) Aptian (125-113ma) Albian (113-100.5ma) Cenomanian (100.5-93.9ma) Turonian (93.9-89.8ma) Coniacian (89.8-86.3ma) Santonian (86.3-83.6) Campanian (83.6-72.1ma) Maastrictian (72.1-66ma) Danian (66-61.6) Selandian (61.6-59.2) Thanetian (59.2-56ma) Ypresian (56-47.8ma) Lutetian (47.8-41.3ma) Bartonian (41.3-38ma) Priabonian (38-33.9ma) Rupelian (33.9-28.1ma) Chattian (28.1-23.03) Aquitanian (23.03-20.44ma) Burdigalian (20.44-15.97ma) Langhian (15.97-13.82ma) Serravallian (13.82-11.62ma) Tortonian (11.62-7.246ma) Messinian (7.246-5.333ma) Zanclean (5.333-3.6ma) Piacenzian (3.6-2.58ma) Gelasian (2.58-1.8ma) Calabrian (1.8ma–781ka) Middle Pleistocene (781–126ka)
Although the raised basin, rim and limestone plateau structure of the Forest of Dean was completed 280 million years ago, the landscape since has changed in innumerable ways; hills have risen and eroded, the vegetation has been tropical and permafrost-covered tundra, dominant lifeforms ranging from plankton to mammoths.
Geology has not left a discernible record in the Forest of Dean during the past 150 million years – but much happened… the tumultuous rifting apart of land west of Ireland, Greenland and North America and the creation of Iceland from a volcanic plume, causing tsunamis, major earthquakes and land masses to sink, rapidly erode, then uplift, and England and Wales as a whole to tilt to the east and south. The White Cliffs of Dover and the chalk laid down when the land was underwater – consisting almost wholly of sedimentary plankton – and flint covers large parts of the south-east, Weald and southern Downs as far west as Salisbury Plain, but is nowhere to be found in the rest of the country. Africa sheared along and under-rode the southern edge of Europe from about 70ma to 30ma, which eventually produced the Alps, the Mediterranean Sea, and the uplands of southern England, from Kent to the Chilterns, the South Downs to the Isle of Wight and Dorset hills.
The Earth survived several dramatic and violent biological and chemical crises, while the landscape spent long periods of time submerged in a shallow sea.
201-174ma shallow sea covers whole of Britain, or at least most of it (some geologists believe the former Midland Platform was again an upland island)
170-152ma shallow sea covers south and east of Dean (coastline a couple of miles north of Severn)
152-145ma sea retreats to south of Bristol Channel
145-110ma intermittent flooding, area mostly land
110-80ma highest sea levels in 600 million years, one-third of world’s land masses underwater (including whole of southern Britain throughout)
80-70ma some land (including Wrekin terrane) dry, but with occasional flooding (in 72ma)
65ma Britain an island shaped much like now
59-14ma further drops in sea level (also rises in 56ma, 23-20ma) : dry land between Ireland, Britain and continent
14ma-now Periods of glaciation interspersed with shorter, warmer periods, sea levels low.
About 100 million years ago, thanks to a complete lack of ice, and bulging ocean basins, a ‘super plume’ of volcanic action in the fledgling North Atlantic which created vast mountain ranges, sea levels rise 200 metres and spill over one-third of current land on the planet, including most of Europe. At the same time, highlands are at an all-time low. The sea is incredibly salty, with a consistency of light maple syrup. Sea-surface temperatures frequently reach 100-degrees Fahrenheit and the climate is mild and constant the world over, with little seasonal difference.
Dinosaurs roamed land near the North Pole, pine woods and “weird monkey puzzle forests” with a climate similar to temperate Britain in 2015, while patches of land further south were occupied by cypress woodlands. Carbon dioxide levels were quadruple compared to now, ensuring polar regions and continental interiors didn’t have winters. If the trajectory towards climate change and greenhouse conditions continues on its current course, this could be the scenario – without the dinosaurs – in less than 250 years in the future (by the year 2264).
The first of a series of planet-wide crises happens in 93ma. Large stretches of water become stagnant, and deep ocean life is starved of oxygen. The perished fish, crabs and marine worms are consolidated into organic carbon within dark mudstones. While the seas covering the Forest of Dean remain shallow and oxygenated, bands of the black shale cover Lincolnshire and Yorkshire, under deep North Sea ocean, with more in the Atlantic. These extreme conditions last for 400,000 to 800,000 years, and the oxygen crisis reoccurs at least once, nine million years later. The shales’ trapping of carbon dioxide gradually causes the planet to cool down.
By 70 million years ago, the sea levels and temperatures have dropped, the climate of re-emerged Britain and Europe becoming arid. Bees, other insects, ants and a prototype of butterflies, as well as flowering plants and leafy trees develop, including magnolia-type blossoms which grow at twice the rate of modern trees. Early marsupial mammals make up but a small proportion of the animal kingdom at first – these become confined to Australia as Gondwana fractures.
Dinosaurs were all the rage until 65ma: Tyrannosaurus Rex, the Velociraptor and Triceratops among the last generation, before a meteorite or comet strike in Mexico (the most likely explanation out there right now) caused their extinction. It was a fair distance away from the Forest of Dean, but the impact of the extraterrestrial collision into a bed of gypsum ejected huge amounts of sulfur trioxide which combined with water to block the sunlight. Anything which relied on photosynthesis was destroyed, and the planet also endured several days of extreme acid rain.
The end result was that ferns and deep-sea species survived, but three-quarters of vegetation and animal species were wiped out. However, the extinction of the gargantuan predators and monstrous herbivores (those not able to fly) allowed new mammal species such as horses, whales, bats and primates to diversify massively, as well as birds, fish and lizards.
At this time, there are two continents, with an oceanic equator: Laurasia in the northern hemisphere and Gondwanaland in the south, North America, Greenland and Eurasia drift – or rift – apart, while Africa, freed from Gondwanaland, pushes in from the south.
The volcanic activity between 60 and 52ma forms many of Scotland’s western islands, the Giant’s Causeway of Antrim on Ireland’s northeast coast, and also Lundy in the Bristol Channel. Dikes left by runny lava flowing through rock fissures, presumably from this event have been recognised north of Chepstow (on its way to Lundy?). The land is uplifted mostly on the same fault lines which had shaped the Dean from a sunken swamp to a raised assymetrical basin up to 280 million years ago, with the Bristol Channel consolidated as a wide valley plain. Some geologists believe the same volcanic chain causes Wales and the west to be lifted up by 2km and for England and Wales as a whole to tilt towards the east and south, while a push-pull effect from the African collision uplifts the southeast and southern edges of England, and forms the topography of London and the Thames estuary.
At about this time, Britain became recognisable as an island for the first time – though within 10 million years rejoined Continental Europe (and mostly since then has remained a large peninsula, rather than island).
Temperatures peaked 55.8ma – conditions have been described as “dense mega-thermal rainforest”. Crocodiles swam off the Greenland coast, while the first primates evolved in the tropical palm forests of northern Wyoming (in the US). India began migrating from Gondwana to Asia – the collision formed the Himalayas (and India continues to press northwards into Eurasia, making the Himalayas a work in progress).
By 35ma, the climate starts to get cooler – beech, oak, redwood, sycamore, chestnut and palm trees thrive, along with grassland, as conditions shift from sub-tropical to temperate. The grass begins to take over and forests thin out to mostly flourish at the Equator after the first ice caps appear in Antarctica. Eventually by about 20ma, all that’s left of the Tethys Ocean between Africa and Europe becomes hemmed in as the Mediterranean Sea. Continents find their modern locations (although they remain constantly moving at about the speed our fingernails grow).
After spending tens of millions of years underwater and then experiencing desert conditions, it’s likely that by 20ma the plateau to the west of the Dean was a low, weathered plain covered in the same chalk found today in south and southeast England, and below that Jurassic mudstones. However as no evidence of a chalk covering has been found whatsoever, not even in rock pockets, some geologists are looking for another explanation. Perhaps the area was devoid of life or remained barren, weather-less and above water?
Climatic conditions caused the land to uplift on more than one occasion, and the absence of chalk and Jurassic rocks has so far been explained by them being washed away in a general downward land tilt to the southeast (the Jurassic layer to the Bristol Channel, Severn Vale and Cotswolds, the chalk and flint further south east).
There was no, or not much of, a Wye valley or gorge, but a river with a similar course similar to the Wye running south of Hereford, probably joined on to the Lugg at the north. The landscape retains traces of its ancient meanders – to the south of Ross-on-Wye, and near Newland, Redbrook, Mork and St Briavels.
The river cut through layers of older sandstone and limestone in increments, especially during periods when colossal amounts of ice melted. The proto-Severn was probably joined to the Thames, which then stretched to Belgium, connecting with the Rhine to form a wider river between England and France, with its estuary south of Kent.
As the climate continued to get colder, the Mediterranean dried up, grasslands spread from river banks to colonise vast plains, as did large mammals. Temperatures warmed up from about five million years ago. By this time familiar wildlife – such as dogs, deer and beavers – evolved, as well as modern plant life.
The Forest of Dean as we know it today was still a long way off… humans would eventually make the trip from Africa, where they began to evolve.
Last 1 million years [1ma-0ma / CE2014]
Living through the ice age
Eon: Phanerozoic (540ma-now)
Era: Cenozoic (66ma-now)
Period: Neogene (23.3–2.58ma) Quaternary (2.58ma-now)
Epoch: Pliocene (5.333–2.58ma) Pleistocene (2.58ma–11.7ka) Holocene (11.7ka–now)
Stage: Gelasian (2.58-1.8ma) Calabrian (1.8ma–781ka) Middle Pleistocene (781–126ka) Upper Pleistocene (126-11.7ka) Pleistocene (781–126ka)
Glacial stage: ISOs 28… Beestonian ISO 16 (676–621ka) Cromerian Inter ISO 13-15 (563–478ka) Anglian ISO 12 (478-424ka) Hoxnian Inter ISO 11 (424-374) Wolstonian/Gipping ISO 6 (374–130ka) Ipswichian Inter ISO 5E(124-119ka) Lower Devensian ISO 5A-D (130–115ka) Upper Devensian ISO 2-4 (71–29ka) Flandrian ISO 1 (14ka-now)
Marine Isotope stages
Warmer periods: 866-814, 790-761, 712-676, 621-563, 533-478, 424-374 (Hoxnian), 337-300 (Purfleet), 243-191 (Aveley), 130-71 (Ipswichian),
AFRICA is our ancestral home: not only – arguably – does the deepest bedrock of the land we stand on (England and Wales) originate from the west of the continent, but we as a species originated there (the earliest clues are found on the east of the continent, in Tanzania, Kenya and Ethiopia). Beyond the scope of this book, in the past 100 years much of our popular music culture has derived from West Africa; cities such as Bristol were built on the backs of African slaves, from the coffee, sugar, cotton and tobacco Africans were forced to harvest on Europeans’ behalf – as was Piercefield Park on the edge of Chepstow.
Western interests continue to ruthlessly exploit Africa: displacing populations and the environment in a quest for oil, gold, diamonds and foodstuffs all in the name of ‘free trade’. In times past, Africans were the bogeymen – barbarians and savages who had to be ‘civilised’ with European Christianity. Now Africa is the prime source for grief tourism. The continent barely exists in the media except as a font for mass abductions by religious and power-hungry zealots, genocides, disease outbreaks, rampaging dictators and famine. Never mind that all these afflictions have occurred in all parts of the world, and never mind that Africa is the cradle of human endeavour, which includes tool-making and art.
The image of savagery which has been synonymous with not just Africa, but anywhere Europeans have colonised, has also extended to anything ‘primitive’. Thus, archaeologists and historians have interpreted according to their world view – they have twisted the Darwinian principle of ‘survival of the fittest’ to mean survival of the most brutal, selfish and ruthless, rather than merely survival of those most suited to their environment. Social anthropology has in many ways acted to negate this temporal chauvinism.
Common chimpanzees to the north of the Congo river may show many signs of altruism and community cohesion, and have their own toolkits which they use for food-sourcing and nest-building. But each community is ruled by an alpha male dictator, who subjugates females. He and his retinue patrol the prescribed limits of their territory, often murdering any other chimp who strays into it.
To the south of the Congo river live the other extant form of chimpanzees, bonobos. They live in larger communities and females collectively manage their society. They are almost wholly peaceful, resolving any potential conflicts with sex (which they perform openly – unlike common chimps who prefer secrecy). Perhaps our close primate relatives – we share more than 98% of the same DNA, making common chimps and bonobos our closest species kin, closer than chimps and gorillas are to each other – demonstrate human traits in the raw. However, the neo-Darwinist Establishment usually falls back on the patriarchal, proprietorial tendencies of the common chimps to explain ‘human nature’ and the course of evolution. However, a great many ‘primal’ peoples studied by anthropologists – those who live hunter-gatherer existences – also practice some kind of sport to avoid violent conflict; many don’t practice patriarchy. It seems that for the vast majority of human existence, violence or male-domination has not played a role, and nor has the obsession with territory, and later empire and nation. In the almost two million years since humans began to evolve, these traits seem to have only emerged in the past 6,000 years to any extent.
Common chimps and bonobos developed independently when the Congo divided them about one million years ago. It is believed that the egalitarian, peaceful and joyful bonobo lifestyle may have flourished due to the ready availability of food sources. Now bonobos are endangered by human hunters and their habitat threatened by the unquenchable thirst for human resources – there are believed to be only 11,000 left.
Humans’ transition from peaceful existence to interminable war, matriarchy to patriarchy, moon-worship to solar sky-god worship, respect for the planet to the ravaging of it, correlates with Saharan desert conditions spreading across the Middle East and western Asia, and the desperate battle for survival and westward push to the more fertile climes of Europe which resulted from the land and resources drying up.
And yet this widening gap between haves and have-nots, where brute strength and technological mass-murder hold sway, is a blip in the scope of one million years of human history. Humans have not only been the only primate species to evolve wholly on two feet, but also the only species to walk away from the trees. Surely the definition of a Forester is someone who connects with an environment dominated by trees?
Variations in the Earth’s orbit are believed to be the cause of the current ice age, which began 2.58 million years ago. Since the first foundation stone of the Forest of Dean was created, there have been two ‘snowball earth’ episodes – in about 710ma and 640ma, when the land was close or in the current position of Antarctica. Then it’s envisaged the planet was covered in ice, except for an equatorial band which may have been slush.
Since then, our land has spent most of its existence in tropical climes. Ice ages of antiquity – between 460 and 430ma, and 360 to 260ma – have not affected England and Wales (but did cover parts of Africa). All the Dean’s resources – limestone, coal and hematite (iron ores), as well as the flint and chalk found elsewhere in the country – have been the result of a balmy climate.
The oscillating glacial episodes of the past couple of million years have wreaked havoc. In one teaspoon of soil you can find more organisms than the global human population. Soil has been essential for terrestrial life throughout its evolution over the past 400 million years. Ice sheets and the polar desert south of the ice has repeatedly scalped the land of all its soil and nutrients, and torrents of meltwater have carved great gashes in the bedrock and washed away layers of geological, as well as plant, fauna and human history. The extent of glaciers messing with landforms is often hard to measure – the Black Mountains bordering Herefordshire and Wales would not be there, or in their location, had it not been for the ice pushing it there – while craggy peaks from Scandinavia were dumped by glaciers on the coast of Yorkshire. ]
The Wye Valley owes its existence to successive glacial periods, as does the Severn and Bristol Channel, and quite probably the valleys cut through the centre of the Forest of Dean, almost bisecting it from Lydbrook to Lydney.
The Earth has possessed the same finite amount of water since whenever it got there (right from the start or soon after forming). The H2O merely cycles from sea to vapour, to rain, to sea again (while there is probably a cycle between the ocean crust and water stored within the mantle, a mystery which we have yet to unravel). When one-third of the planet is iced up, the frozen water means sea levels must be much lower. The ice also planes down the land, and when it melts results in the land springing up, free of its heavy weight. As the ice sheets are thickest in the north of Britain and will generally melt to the south, England and Wales is now sinking at a rate of 5mm per year (the eastern side more than in the west, although the Bristol Channel is one of the most rapidly sinking areas), while Scotland is on the up. This general trend of the south-east pushing down and northwest rising up translates to the entire Eurasian landmass, with the nearest volcanic areas to us – Iceland and Italy – remaining active as we continue to rift away from North America in the mid-Atlantic, and the African plate continues to subduct in the Mediterranean. Meanwhile, India continues to push into Asia, while out in Japan, the Philippines and Pacific Eurasia causes friction with that end of the Americas. The ongoing tectonic plate jostling can only be exasperated by the periodical predominance of ice.
Between 814ka and now we have experienced 10 glacial periods in Northern Europe. Animals and plants seized any window of warming climate to colonise the nascent Forest of Dean and Britain, only to perish or emigrate south each time the ice returned.
Humans (and many other mammals) could be seen as a product of the ice age, although their roots are in a warm climate. The tall, thin figures of the first human incarnation, Homo Erectus, most closely resemble the bodies of those who live in hot Africa, while the thick-set form of the Neanderthal, which originated in ice-house Europe, is closest to that of Inuit Eskimos of Greenland.
Debate over the succession of Homo species and their evolutionary paths continues – but at the time of writing it does seem that anatomically modern humans (Homo sapiens sapiens – translating as wise, wise man) originated in East Africa about 200,000 years ago. While Mitochrondrial Eve, our matrilineal most recent common ancestor (from whom all living humans descend, in an unbroken line, on their mother’s side, and their mother’s mother and so on). Is said to have lived between 100,000 and 200,000 years ago somewhere in East Africa, our paternal common ancestor Y-chromosomal Adam lived somewhere between 120,000 and 338,000 years ago, depending on conflicting studies (and if we accept the earliest date, he came from Cameroon, in West Africa, and there is upwards of nine evolutionary mutational steps between ‘Adam’ and us today).
Archaic human species made it out of Africa as long ago as 1.8ma, to Dmanisi in Georgia. New discoveries in Happisburgh, Norfolk have pushed back their reaching England to as far back as 950ka. Then they encountered a climate between one and four degrees Celsius cooler than now, populated by grassland and pine trees. Signs of humans have also been found at Happisburgh between glacial periods (known as interglacial) 850ka, 780ka and 712ka, and in Pakefield, Suffolk, for the latter two periods. It’s likely that between 814 and 790ka, and 761 to 712ka the climate would have been too cold. In 790ka, Happisburgh settlers were on the edge of a proto-Thames river, while in 712ka the climate was up to a couple of degrees warmer in summer (similar to the Mediterranean today) and a couple of degrees colder in winter. They lived among oak, elm, hornbeam, hazel and lime trees.
It isn’t until 533ka that excavations reveal humans got anywhere close to the Forest of Dean – they left signs behind at Westbury-sub-Mendip in Somerset. These meagre findings were eclipsed by the array of tools and bones found at Boxgrove, Sussex. By about 500ka humans and other flora and fauna would have been long gone, as perhaps the most severe glaciation of this ice age, known as the Anglian, saw ice sheets cover everywhere north of and including Bristol and London. The Thames was diverted to its present course once the ice melted, and for at least 20,000 years from about 400ka, southern England (at least) was inhabited by people. During this time the English Channel repeatedly opened and closed, meaning Britain assumed different island forms.
From about 300ka Neanderthals began to proliferate in Northwestern Europe, following mammal herds to southern Britain, particularly the London area, but also near what is now the southern English coast. Tools had diversified from being mainly hand axes to a variety of forms for all kinds of purposes – although Pontnewydd in north Wales was a centre for hand axe manufacturing. Although a glacial period, high levels of solar radiation prevented extensive ice sheets from forming – a small one in the north melted very slowly. Materials for tools travelled a maximum distance of 30km. Paul Pettitt and Mark White, in their book The British Palaeolithic: Hominin Societies at the Edge of the Pleistocene World report: “Recent work (Clinnick, 2010), suggests that maximum raw material transfers do not reflect cognitive clout but the minimum predatory range needed to sustain healthy bodies and healthy social relationships amongst large-brained, carnivorous hominins [humans] living in fission-fusion societies [where social groups change according to circumstance, gathering to sleep together and splitting into smaller groups to forage].”
Then, from 250ka, for the next 200,000 years, there is no human record in Britain. While for all we know there may have been a thriving Neanderthal civilisation in the Forest of Dean and elsewhere in the country at times during that long period, the tumultuous climate changes have so far frustrated any evidence. What we do know is that there were high sea levels around the south coast from Cornwall to Essex from about 250ka, and it’s probable that Britain was cut off from continental Europe. During this time oak, hazel, birch, pine, maple, alder, lime, spruce, ash, ivy, grasses and sedges thrived.
There’s also no sign of humans during an especially warm stage between 130 and 115ka, known as the Ipswichian. It seems hippopotamuses may have been at the top of the food chain – one dating from about this time roamed London and met his demise under Trafalgar Square, another wallowed as far north as Leeds. The bones of Arctic hares, wolves, brown bears, badgers, spotted hyaenas, wild cats, lions, straight-tusked elephants, narrow-nosed rhinoceroses, wild boar, red deer, fallow deer, giant deer and bison dating from this time were found in a cave in Buckfastleigh, Devon.
Most of these mammals disappeared during a major cold snap about 90ka, to reappear less than 40,000 years later. Humans also returned to Britain when it again ceased to be an island.
And within several thousand years we have the first possible evidence of a human presence on the edge of the Forest of Dean, leading us out of geologic and ice-age deep time and the end of Part 1.
Part 2 coming… whenever