Strange Geographies
A Preface
If you're not a Palaeogeography geek – and odds on you are not – then you probably struggle to make coherent sense of what you know of early Earth.
The story plays out over billions of years and, while geologists have helpfully sliced it into Aeons, Periods, Epochs and Ages, there is constant change within each. Can you place the birth of the moon, snowball Earth, and Jurassic Park within this? Do you want to? It seems to be like a four-dimensional Rubik’s cube, where each little cube represents a slab of the Earth’s crust which can change its position, shape and colour.
There are YouTube videos of the movements, but while pretty, they are often contradictory, confusing or just wrong. Part of the problem is the labelling. Do you need to know that synapsids and sauropsids were on the rise in the Permian, late in the Palaeozoic era of the Phanerozoic aeon? I suspect not.
For my part, I am happy to leave this type of detail to geology’s trainspotters and to people looking for places that might be good for oil or bad for volcanoes. All I want is to understand the big picture and have a mental map and broad sketch of the story, to provide a dramatic playground for my imagination.
The first period of Earth’s history was aptly named after Hades, the Greek Hell, a fire-and-brimstone nightmare. At one point, it might have crashed into a planetoid, creating the moon, which, for a long time, was much closer to Earth than it is today. (In Greek mythology, Gaia is the personification of Earth. She created Uranus, the sky, as a companion. Their children were Titans, one of whom was Thea, whose name has been given to the doomed planetoid).
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| The Hadean Period |
Big brains have done a job in working out what emerged after the worst of this was over, and it turns out that Genesis almost got it right. After that tumultuous start, the Earth was indeed formless and empty, but now a bit less like a fireball and more like a planet. As a bonus, the methane belched by the volcanoes created an atmosphere.
As a reward for their hard work, the Brains got the naming rights. There is no helpful pattern. Eras, ancient continents and oceans got names fished from legends, ancient tribes and historical tatters. There are more Titans, lots of Titans; ancient tribes, myths and some places which were key to advancing geological understanding.
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| Titans |
I like to picture these places in my mind's eye, even though the view is hazy at best. It is more satisfying than picking a totally imaginary ‘ready to wear’ out of a book or off a screen. So, this is the drama of Planet Earth. Somehow I can’t forget the early years of Dr Who on planets with polystyrene boulders scattered around flat studio floors.
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Skaro
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The Prelude:
Throughout the story, the views, the climate, the air, the Beasts that Lurk and indeed nearly everything on the planet, constantly and dramatically changes. Even a good mac, gas mask and elephant rifle wouldn’t get you through it. It’s just too much. Suffice it to say that for a long time, life was underwater and invariably hungry. Later, on land, tiny strange beasts were followed by bigger strange beasts and then the reptiles whose demise (climate? meteorite?) made room for animals like…...you know the rest.
Act One
Earth is over 4.5 billion years old and no longer in the first flush of youth, but it is belatedly maturing. In places, on the infernal surface, bigger lumps of the Earth’s crust rose to the surface and congealed. They were the first continents, and all the changes that followed have effectively hidden them from us. For all we know, there could have been luxury resorts for little green men.
Undaunted by ignorance, the name-givers got to work, creating an alphabet soup of hypothetical lands on the slabs of crust. Vaalbara, Ur, Columbia, Nuna and many others might have existed. And might not. If they did, they didn’t hang around. It took a very, very long time for things to settle down. By then most of the planet was deep under water and, above the water, methane. Some microbial life appeared.
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| Rodinia |
Around a billion years ago the lumps grew and merged to become a major landmass, ‘Rodinia’. The name comes from the Russian for motherland but, lacking self-awareness, it didn’t know that. There were smaller lumps elsewhere; one putatively comprised the appealing combination of what is now San Francisco and the Congo!
Rodinia would probably have been hot, bleak, dusty-red and lifeless. Maybe it would have looked a bit like the set of ‘The Martian’, which I believe was filmed in Wadi Rum in Jordan, but with added poisonous yellow clouds and storms. It survived for half a billion years, but eventually broke up.
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| Wadi Rum / The Martian |
Like any celebrity divorce, this one was mucky and had consequences, one of which was a massive reduction in the methane and global cooling. Why? Climate history is a gas, but space does not permit me to go into that here. Anyway, this turned the planet from an oven into a freezer – snowball Earth. That snow wasn’t like our damp stuff; it fell in clouds of crystal dust and was the purest imaginable.
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| Snowball Earth |
But while the methane was down, it was not out, and the volcanic goings on beneath the Earth's surface meant that it returned. At this point the plot begins to accelerate; there was a rapid climatic bounce back and an explosion of life. At first it was limited, mostly ground cover like lichens and liverworts. Later, it was not obviously vegetable or animal and very, very weird. Wikipedia refers to ‘discs, tubes, mud-filled bags or quilted mattresses’ and I will take their word for it.
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| Lichens |
Another continent, Pannotia, might also have flickered into and out of existence. Its demise triggered the birth of the new Iapetus Ocean. It follows from the constant movement of continents that seas live and die as well. (Iapetus was also a Titan. Their names are now given to the moons of Saturn).
Act Two
Individual species come and go, but this whole history suggests to me that life is determined and resilient. While it is hard to believe that a species capable of inventing the TikTok Ring Auto-Scroller could achieve its own demise, it does invite the question of what might spring up in its stead. Maybe something, somebody, better designed, with no appendix or tail-bone and a greater talent for co-operation?
What emerged from under the ice was a huge ocean, Panthalassa (Greek: meaning all-sea), the deep ancestor of the Pacific, and a massive southern continent, Gondwana (named after a forest tribe in the middle of India). The latter included reassembled fragments of what had been Rodinia, and which would one day become Africa, Latin America, India and the other southern continents, and other chunks of crust that would later drift northward and join new landmasses there.
We know that all this was a real thing because Gondwana has its own journal, which, if you take a look, will convince you of the wisdom of my claim that the detail kills the story. Link: Gondwana
There is also a (quite good) Chilean reggae band named after it, who have over 2m listeners on Spotify. No other early super-continent has been so honoured!
It was around this time that life really got going, virtually entirely underwater and especially in the shallower seas and littoral areas. This was the ‘Cambrian Explosion’. Initially it seemed to involve creatures akin to animated bath mats scuttling between massive fronds. The distinction between creature and plant wasn’t always clear. Later, it got really strange and makes you wonder what the deity had been smoking.
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| The Cambrian Explosion |
While most of the action was in the southern hemisphere, a number of smaller blocks had merged in northern waters. Baltica, Laurentia and Siberia came together, firstly to form Euramerica and later to form Pangea, a handy Greek word meaning all-land. At this point, someone noticed that, in the past, the shape of the blocks suggested that Africa must have slotted neatly into South America. Obvious with hindsight!
At this juncture, words cannot convey the complexity of the movement of the various landmasses. Animation helps. Here is one from Cambridge Uni that focuses on what became the UK. UK Centric view of Continental Movements, Many more of these videos can be found on the website and YouTube channel of an American paleogeographer, Christopher Scotese. One of them is here: Link: Scotese YouTube . This one takes a different approach, letting you see what is where at any particular time. Link: The Globe through history His website is here: Link : Scotese Website.
Over time, Gondwana itself drifted north, closing the ‘Rheic Sea’, named after yet another titan, and which separated it from the northern landmass. This coup of geological imperialism consolidated a single globe-spanning continent called Pangea.
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| Pangea |
By now, there was some plant life on the edges of the barren land: mosses, liverworts and green slippery stuff underfoot. This accelerated as the landmass slowly moved towards the equator, and you might have seen Prototaxites, things the size of trees but which were probably giant fungi!
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| Prototaxites |
ACT 3
This new super-continent of Pangea spanned and split the globe, and triggered the start of the Carboniferous period. By the time that had ended, the planet was green, covered in swampy forests that lived, died and left us the devil’s gift, coal.
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| Carboniferous Landscape |
By this time, a walk in the woods was getting a bit more worrying, with the rise of giant insects.
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| Arthropods |
These continents move as fast as your fingernails grow, so the collisions, while incredibly violent, always happen in slo-mo. That’s a shame, for a species that seems to enjoy watching car crashes on TV, it would be great to be able to rewind and accelerate a 100 million year crash to, say, ten minutes.
I see the potential for a video game based on wars between Pangea and Pannotia, with armies dressed in the uniforms of the Austro-Hungarian empire and against a backdrop of Carboniferous forest and volcanoes. Because, by this time, you had forests as well as volcanoes.
And this brought another advantage. All the new greenery introduced more oxygen into the atmosphere. For the first time in Earth’s history, time-travelling tourists would be able to breathe the air and, if you didn’t go swimming, were in little danger. One problem they might have, though, is jet lag. The planet revolved more quickly then, so the day was shorter by several hours. Nights would sometimes have been brighter though - the moon was still a good deal closer than it is now.
Pangea also eventually broke apart, so there was no longer a supercontinent spanning the globe, and the various fragments began a slow waltz around the planet looking for others to hitch up with. By the time they had finished, ‘Laurasia’ had formed in the north and comprised what became most of Asia, Europe and North America, while in the south Gondwana, separated again, included just about everywhere else. A narrow but growing (and still growing) sea called the Atlantic had split Africa from the Americas. In the south, Antarctica and Australia parted company, and India headed northwards, eventually crashing (and still crashing) into Eurasia, creating the Himalayas as scars on the wound.
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| The Himalayas |
Got all that? I did say it was confusing, but at this stage the pieces of the jigsaw are not all in place, but you can see a pattern emerging, even though the continental breakdancing isn’t done and never will be. An archipelago sits in a shallow sea at the edge of the northern landmass. Part of it will eventually be inhabited by a species capable of accidentally changing the climate while focusing on more important things like house prices. Here, I will leave the main thread of the story and digress.
Through most of the story, the flora and fauna only play bit parts. As those early oceans grew, those microbes turned into sea creatures, getting bigger and more bizarre. I wish that I had space for that, having moved off from the idea of a sentient mattress and skyscraper fungi to a world whose layout is a tad more recognisable, even if the wildlife is not.
But at this stage in the main plot we are in the Jurassic period, so you can start to imagine big reptiles. They had actually appeared earlier, but the massive creatures loved by kids of all ages began to dominate now and reached their zenith in the later Cretaceous period.
Some of them were carnivores, but many would have been veggie if not vegan. They were well catered for, although there wasn’t much around to excite gardeners. The greenery was abundant, but there were probably few coloured flowers and the grass we are familiar with is actually relatively recent.
As I bet you know, a meteorite collision or similar disaster provided a coda for the Age of the Giant Reptiles, their legacy being the avian feed-stock for the fried chicken shops.
If you want a feel for what the world looked like in the various stages of its journey, you might try the Hitchhikers Guide to Prehistory podcast: https://prehistoryguide.buzzsprout.com
If you want an equally brief but rather more technical express trip through Earth’s journey, try my earlier post here: https://www.pootler.co.uk/2022/02/the-jurassic-paddling-pool.html
EPILOGUE
Laurasia and Gondwana, the splintered remnants of Pangea, were now separated by an immense tropical ocean, Tethys, which for 250 million years girdled a planet which for a while was nearly 80% sea. Tethys was yet another titan and the goddess of fresh water. Together with hubby Oceanus, she secured their lineage by having 6000 children. Its life and strangulation death are a story in itself, and one worth telling.
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| Thethys |
It was only 6 million years ago that Africa was pushing northwards in a movement that created the Alps. This movement cut the Tethys Ocean in half, leaving its western end as the Mediterranean and a few puddles, namely the Black, Caspian and Aral seas. This sealed the demise of the ancient Med. Lacking enough refilling from rivers, it evaporated and became a massive, low-level salt desert.
Eventually the Atlantic, rising to the west, broke into its basin. This was the Zanclean Flood, and it would have been a sight to see, if there had been anyone there to see it, perhaps sitting on the Rock of Gibraltar. A torrent of water thousands of times greater than today’s Amazon River filled the Med at up to 10m per day until it became a sea once again.
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| The Zanclean Flood |
The demise of the Eastern end of the Tethys came earlier and was perhaps even more dramatic. When Gondwana broke up, India headed northwards at what was, for a continent, a sprint. Perhaps 20cm a year. When it crashed into Eurasia, it squashed Tethys, buckled and raised the sea bed to form mountains which I have walked. The Himalayas are part of the Tethys seabed! Another legacy of the teeming life within it was the oil fields of the Middle East.
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| Everest |
Finally, a bit for the futurists and sci-fi fans. Because the continents float around on blocks whose direction of travel is known, you can work out where they might end up, with some accuracy in the (geologically) short term, and more speculatively after. Here is an animation: Link : Future Earth
Opinions differ, but a tentative summary is that the Med is doomed. The Pacific will shrink while the Atlantic expands, putting clearer, blue water between us and the Americans. East Africa will split from the rest and Southern California will hurtle north along a fault, heading for Alaska. Australia is nippy, tectonically speaking, and heading north at a rate.
Many think that a super-continent might form again one day, although when and how is moot. Already, the name game is being played, but so far with a paucity of creativity. So we have Proxima Pangea, Aurca, Amasia, and Pangea Ultima. You can see the BBC analysis of the possibilities here: Link: Future Supercontinent
We can only hope someone is around to see it.
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| Future Supercontinent? c/o BBC. |