Avalonia

Intro

 
Please keep in mind that this is an attempt to give you a sense of the story of Avalonia, not an academic-standard account of geology or palaeontology. And 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 I can. 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. 

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 we call Gondwana, amid the Iapetus Ocean. (It was a precursor of the Atlantic, which takes its name from Atlas, whose father was Iapetus). (Note # 2). 

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. The planet revolved more quickly, so the days were shorter and, partly because of a lack of plant life, there was much more carbon dioxide, so unprotected time travellers would have trouble breathing. 

The moon was much closer then, and 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. Think of something similar but larger than Japan and also part of an arc of volcanoes. Continents are always on the move. 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. 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 geology is mirroring politics and the North American and Eurasian plates are moving away from each other. 

Iceland: The Continental Divide

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

For some time the seashore had hosted algae, lichens and microbial mats. While the sea itself was full of life, our knowledge of it is limited by our reliance on fossil evidence, and 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.

But now, on the land you wouldn’t have seen as much movement, but by the time the collision started you might find 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, growing by spreading and without leaves or roots. Early arrivals included giant tubular fungi the size of trees but without branches or leaves. They look a bit like monster, upright cucumbers. Or worse.  

Prototaxites

It is hard to know exactly when sea creatures evolved legs and crawled out of 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 seem to also use it 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. 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 larger than a house 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 and, since the bugs and fungi that hastened their decay hadn’t mastered that art, they stayed buried under later rock layers. Later they became coal. 

Carboniferous Forest

What you would not have seen is grass, and neither would you have heard birdsong. Neither came along for another few hundred million years, but in the absence of many predators, insects were thriving. You might see millipedes 6 ft long and predatory dragonflies big enough to terrify a Blackpool seagull. You would also find reptiles, not the giants that appeared very much later, but creatures who were often herbivorous but big enough to retaliate if you annoyed them. But some were 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. Unsurprisingly, life bordered on extinction after natural catastrophes ranging from renewed vulcanicity to asteroid strikes.

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'.

A favourite of mine is the sail-backed synapsids, which flourished and then disappeared in the massive extinction event. It was carnivorous, around the height of a man, and twice the weight, but they were at least easy to spot at a distance! What is the use of that sail? What were the gods of evolution thinking of? 

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 and whose fossils were found near Glastonbury, but well before the giant dinosaurs times. Whoever named it had a sense of humour! It looked a bit like we imagine dinosaurs, but in fact the time between them and, say, TRex was longer than between TRex and you.  

Camelotia 

The collision would have taken millions of years, during which Avalonia was still close to the seas. But much later, it was increasingly caught in the middle of the new continent, and 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 a lack of water and an atmosphere that, by the Triassic period, contained a bit less oxygen but a lot 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.

These layers might only accumulate at one centimetre every millennium, slower than the build-up of dust on my floor. 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. 

At this juncture, I sideline any interest in Avalonia’s American branch and Newfoundland. 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 stand on 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 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 #3 

But now, I must conclude my tale. So, what’s in a name? 

 Avalon emerged from Brythonic myth as an island in Somerset and a setting for a ripping and politically motivated yarn, later perpetuated by a fraud. Later, it migrated 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. 

Ouroboros

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. 

I just love the idea that the ancient, semi-mythical Isles of Avalon are founded on the primaeval gnarly gneiss, granite and volcanic legacy of Avalonia. As is most of England! 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. 

So Geoffrey of Monmouth, wrong in so many things, got this right!

GEEK NOTES

# 1   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. 

# 2     I love the names of the ancient seas. Miravia was a major ocean before Gondwana. The huge Panthalassa Sea surrounded Pangea and became the Pacific. And Tethys played a big part in the later history of Britain.

# 3 

Outcrops on Caer Ceradoc

Volcanic Ring