Avalonia

 Intro

 
Please keep in mind that this is an attempt to give you a sense of the story of Avalonia, not an academic account of geology or palaeontology. It is hard to get your head around the technical vocabulary and astronomically large numbers involved, so, for my own sake as well as yours, I will avoid both and include as few dates and labels as possible. Honest. But there have to be a few.

1. In the Beginning 

The Earth is around 4.5 billion years old. For a long time, it had been a hellhole, bombarded by meteorites with belching volcanic lava fields and no meaningful atmosphere. But over time it calmed down. 

This tale starts relatively recently, a mere 500 million years ago. By that time, sea levels were much higher than they are today and the sealife was rockin' and, in the shallow seas in particular, increasingly anti-social and unfriendly. I am not going to dwell on it here, not even the animated bath mats, but a general lesson for the next half billion years is, if you must visit, don't go swimming even though some of the creatures are simply entertaining. (Note #1) 

Most of the planet’s land was in a giant southern continent amid the Iapetus Ocean, a precursor of the Atlantic. We call it Gondwana.

Iapetus

It was no tourist destination, having morphed from a barren volcanic wasteland inhabited by little more than microbes to a place only marginally more godforsaken; bleak, mountainous, silent and probably still shrouded in clouds of volcanic dust. There was hardly any plant life, so there was much more carbon dioxide in the air. Unprotected time travellers would have trouble breathing. 

The planet revolved more quickly then, so the days were shorter. And the moon was much closer. Its gravity meant that oceanic tides must have been dramatic,

Just off the Western Shore of Gondwana was the large island slab of the Earth’s crust that Harold Williams was later to name Avalonia. In shape, it was similar to Japan, but larger, and also part of an arc of volcanoes. Continents are always on the move, albeit at about the rate our fingernails grow. (Note #2). Around 500 million years ago, it cut adrift and headed northwards on a 100 million-year journey across the lively and increasingly dangerous Iapetus Ocean, towards the equator. 

The video below traces the position of what was part of Avalonia and which became the UK in its passage from Gondwana and the South Pole to its current position. It is a simplification; the shape changed over time and southern England spent much of the later part of its life underwater.  Link: Continental Drift

Eventually, Avalonia collided with two Northern land masses, Baltica and Laurentia, and in doing so helped to collapse the Iapetus Ocean and create mountain ranges. One result was the mountain chains raised where they crashed into each other. The Alps are a good example, but the hills of Scotland and Wales also started that way, at around the start of this tale. And when they split, they can leave a fissure. This is currently happening in Iceland, where the North American and Eurasian plates are moving away from each other. (Not fast enough, you might say). 

Iceland: The Continental Divide

Also, as you might expect, as it approached the equator, it got progressively warmer, wetter and greener, becoming a place where, as Mr Spock never actually said, ‘there’s life, but not as we know it’. 

The surrounding sea itself was full of life, although our knowledge of it is limited by our reliance on fossil evidence. Many of the soft-bodied invertebrates which seem to have predominated don't leave bits of themselves around to please the fossil hunters.  I rather wonder if it was simply by chance that what we laughingly regard as intelligent life developed on land rather than in the seas. Note #4

While at the start of Avalonia's northwards journey, the seashore probably hosted algae, lichens and microbial mats; on the land you wouldn’t have seen as much movement. But by the time of the collision, you might have found the first plants appearing; simple things like liverworts and mosses and, later still, some enterprising creepy crawlies. 

Plant Life: A modest start

There might also have been creatures at home on either side of the waterline who might visit the shores to feed on the meagre pickings or escape the predators in the subsea horror show. But it was the start of the long journey over the hundreds of millions of years that followed, to forests, topiary, wasps and the Chelsea Flower Show.

Even if you are familiar with today’s tropics, this would have been a strange landscape. At the start, the ground itself was probably reddish; it takes time for organic decay to change the colour of the sandy soil. Most of the plant life was ground cover, spreading and lacking leaves or roots. Early arrivals included giant tubular fungi the size of trees but without branches or leaves and looking a bit like monster, upright cucumbers. Or something else.   

Prototaxites

It is hard to know exactly when sea creatures evolved legs and crawled out of the brackish water and onto the Avalonian seashore. It certainly isn’t an unnatural thing to do. Today in the tropics, you might see mudskippers, which have separately learned the same trick (they can climb Mangrove trees) and seemingly do so to attract a mate with their dance moves. Seriously! I include the picture below because I want a mangrove swamp for a garden and one of these piscine romeos for a pet. 

Mudskipper

Don’t think of all this as being steady progress. A lot can happen over several hundred million years. Sometimes it was wet, dry or cold; but it was often verdant, with jungles of giant ferns and increasingly tree-like trees, with ginkgos and palm lookalikes. The mix might have looked odd, the plants less so, although some like horsetails and club mosses would make those we see today look Lilliputian. That doesn’t surprise me. I have seen heather bushes the size of mature apple trees in the mountains of East Africa.

Later, in the increasingly oxygen-rich atmosphere, slightly less odd giant trees grew. Because they didn’t root deeply, they often fell over like Saturday night clubbers. Since the bugs and fungi that hastened their decay hadn’t mastered that art, they stayed buried under later rock layers and gradually morphed into coal. 

Carboniferous Forest

You would not have seen any grass or heard birdsong. Neither came along for another few hundred million years, but insects were thriving in the absence of many predators. You might see millipedes 2 metres long and predatory dragonflies big enough to terrify a Blackpool seagull. There were also reptiles. These were not the giants that appeared very much later, but often herbivores who were that were smaller and lighter, but still big enough to retaliate if you annoyed them. Others were simply cute. The pic below is a reconstruction of a flying lizard.

Coelurosauravus

At other times the climate changed from periods of intense heat to arctic cold, the atmosphere from oxygen-rich to poisonous and sea levels which alternately shrank continents and oceans. There were also natural catastrophes ranging from renewed vulcanicity to asteroid strikes. Unsurprisingly, life sometimes bordered on extinction. 

The Permian Extinction

Our mammal ancestors didn’t arrive until the very end of this roller-coaster story, and in the shape of tiny mouse-like creatures which were a fairly insignificant part of the menagerie of weird creatures emerging from nature's skunk works. I love David Mountain's description of them as 'Pokémon designed by H P Lovecraft'. (Note #3) 

A favourite of mine is the carnivorous sail-backed synapsids, which flourished and then disappeared in the massive extinction event. They were around the height of a man, and twice the weight. What is that sail for? What were the gods of evolution thinking of? But at least it made them easy to spot at a distance. 

Dimetrodon

You and I are also synapsids, and thus more closely related to this beast than you are to the dinosaurs, which are reptiles. Who’s weird now? And might a future iteration of life on Earth be intelligent reptiles? 

But all this was a mixed blessing for Avalonia. At this stage, life as a whole was thriving, give or take the dramatic fluctuations in the climate and the odd extinction event. The early relatives of dinosaurs and crocodiles had appeared. The latter would probably have been significantly more dangerous, adding a frisson of jeopardy to a waterside paddle. 

Given that this is Avalonia, I particularly liked the Camelotia, a giant herbivore that lived long after the sail-backed oddballs, but well before the giant dinosaurs' time, and whose fossils were found near Glastonbury. Whoever named it had a sense of humour! It looked a bit like we imagine dinosaurs, but in fact the time span between them and, say, TRex was longer than between TRex and you.  

Camelotia 

The collision itself would have taken millions of years, during which Avalonia was still close to the ocean. But as the millennia passed and the continents continued to shuffle around, it was increasingly caught in the middle of the new continent. 

A burning, mountainous desert in the middle of a continent can be an unhappy place to be. Think Australia, Niger or even what we know of the surface of Mars. You don’t find much wildlife there. My favourite comparison is with Wadi Rum. You might have seen it in films like The Martian. 

Wadi Rum in Jordan 

(Ironically, desertification might have helped the development of the giant dinosaurs which came very much later. Their egg-laying and Gore-Tex-style skin gave them an advantage over their evolutionary predecessors when living on the margins and coping with an atmosphere with less Oxygen and more Carbon Dioxide. 

Over time, the world warmed, water levels rose again, life bounced back, and Pangea broke apart. Some of the land that had been Avalonia was now on the East Coast of North America, while the rest of it was slowly shuffling towards the spot it now occupies on the North West Coast of Europe and separated by, and frequently submerged under, the new Atlantic Ocean. You will get some idea from the gif below. 

At the bottom of the sea, the original igneous rocky base of Avalonia was smothered by thick layers, firstly of sandstone and then of limestones, which are comprised of both sand and the skeletal remains of trillions of small sea creatures that you see today.

Once again we encounter the impact of slow changes over unimaginably long periods of time. These layers might only accumulate at one centimetre every millennium, slower than the build-up of dust on my floor. Even at that rate, the layer would be higher than Beachey Head within 20 million years, and we are dealing with much longer timescales than that here; the only reason why the chalk layers are not deeper, and Beachey Head higher, is subsequent erosion.

At this juncture, I will sideline any interest in Newfoundland or the rest of Avalonia’s American branch. Frankly, you cannot forge an identity or claim roots on the back of a name which had been borrowed from the personal dreamland of a Jacobean God-botherer. The place must stand or sink on its own merits. 

Avalon, Newfoundland

I can also conclude my story of Avalonia as a place on Earth. The fractious shenanigans of the various land masses, the dramatic changes in the climate, the era of the dinosaurs and, after yet another great extinction event, the rise of the mammals, all pass it by. I can return to the recognisable world of England and specifically the Somerset Levels.

Underneath the Levels are those very thick layers of limestone and sandstone together with the various types of compressed mud, peat and gravel left behind after more recent inundations. 

Below all this is the ancient bedrock of Avalonia. Depending on where you are, and what period you want to dig down to, you might have to dig at best a deep hole and at worst something deeper than Britain’s deepest coal mine. This is how it works out: old Avalonia is the Cambrian layer at the bottom. 

The upshot is that if you want to see what’s left of Gondwana or Avalonia in this area, look for places where Earth has shoved bits of it towards the surface and left erosion to uncover whatever else lay on top of it. You can see it at Moon’s Hill Quarry in the Mendips, where they mine Andesite, which is the Avalonian lava. (You might also see Andesite on Mars or, with less difficulty, on kitchen work surfaces!). 

Or better still, if you want to stand on it, go further afield, perhaps to Caer Ceradoc, near Church Stretton, which is a remnant of a volcanic field dating back to Avalonia’s time within Gondwana. There, you can look down on a fault created by one of those early continental collisions and which would once have been as substantial as the famous San Andreas fault that threatens California. I made a point of climbing it to take some snaps just for you. Note #5

But now, I must conclude my tale. So, what’s in a name? And have you heard of the ouroboros, a symbolic snake which is eating its own tail? It appears in old English texts as well as the Book of Kells and also as Jörmungandr in the Norse myths. Apparently (and I have only just discovered this!) it represents eternity and the circle of things starting over again after they end. This seems apposite here. 

Ouroboros

Avalon emerged from the Brythonic myth of the 'otherworld', a mysterious, enchanted place beyond life and death. In the High Middle Ages, a teller of tales identified it as an island in Somerset and a setting for a ripping and politically motivated yarn, later perpetuated by a fraud. 

Later, inspired by a link with the story of Christianity in England, the name optimistically pinned to a cold, wave-lashed peninsula in the New World where, many years later, it was co-opted again, for the 500 million year old igneous rock topping on a desolate tectonic plate near the South Pole. Finally it set off back home to where it started from, becoming the stone basement of Southern England. 

I just love the idea that the ancient and mythical Isles of Avalon, journeyed through medieval folklore and invented history, are associated with the primaeval gnarly gneiss, granite and volcanic legacy of Avalonia which now underpins them.   And if I were to burrow down from where I am sitting, through the blue-grey London clay and the thick layers of chalk left by ancient oceans, here too I would find myself on ancient Avalonia. Like the Ouroboros, the tale has eaten itself and Geoffrey of Monmouth, wrong in so many things, got this right!

GEEK NOTES

# 1     I love the names of the ancient seas. Miravia was a major ocean before Gondwana. Iapetus was the father of Atlas, and the ocean's demise created the eponymous mountain range. (Note # 2). Later, the huge Panthalassa Sea surrounded Pangea and became the Pacific. Later, Tethys, another sea, played a big part in shaping Britain.

# 2  I have no idea what its top speed was, but England is currently moving away from America at around 2cm a year, while Japan straddles four plates, all moving at different speeds, with the fastest sprinting northward at around 10cm a year.  Hence their earthquakes, tsunamis, etc. 

#3   If you fancy touring early Earth, try David Mountain's entertaining podcast series. It's available on lots of podcast platforms.

Here is the Spotify Link: The Backpacker's Guide to Prehistory

# 4   Nature creates some strange things. I particularly liked these two sea creatures, both of which existed before this story began. 

Opabinia probably used the long proboscis to pass food to the mouth under its five eyes! 

Hallucigenia. It took scientists years to figure out which was the 'head' end. I just like the name. 

# 5

Outcrops on Caer Ceradoc

Volcanic Ring