A compilation of episodes of the history of Earth and the Dinosaurs.Discover our full back catalogue of hundreds of videos on YouTube: https://www.youtube.com/@astrumspaceFor early access videos, bonus content, and to support the channel, join us on Patreon: https://astrumspace.info/4ayJJuZ
Chapter 1: What events shaped Earth's early atmosphere?
Earth is the place we call home. It's where we work, eat, sleep and go about our daily lives. But how well do we really know it? We like to think of Earth as the blue marble, a stable, temperate world hospitable to life. But that's really just a snapshot of a dynamic and evolving planet.
If we zoom out on the cosmic timeline, we discover that our home would have been unrecognizable to us at most other times in its history. So, let's see if we can reconstruct what Earth might have looked like in the distant past. Let's imagine that alien scientists, who have never seen Earth as it is today, visited at various stages in its development.
Depending on when these visitors arrived, they would have formed completely different ideas about the kind of planet Earth was. What would they have seen 4.5 billion years ago? 2 billion years ago? Half a billion years ago? I'm Alex McColgan and you're watching Astrum. Join me today as we recreate Earth's ancient past and imagine what the planet might have looked like at various points in time.
Now, before we start, a little disclaimer. To answer these questions, we'll need to draw on some models that not all our scientists agree on. Travelling into the extremely distant past always carries some error bars. Some of the science we're pretty sure about. Other things are still being debated.
So, as we indulge our imagination, let's keep in mind that some of these claims are still being developed and rigorously questioned, as they should be. But to the best of our current knowledge, this is what our planet could have been like. As long as we're going into the past, we might as well go way back. Let's start 4.5 billion years ago. It's not the very beginning, but pretty close to it.
At this time, the Earth is basically a hot, viscous ball of molten rock, and I doubt our alien visitors will want to hang around for very long. The Earth is still young, not even 100 million years old yet, which in planetary terms is an infant.
Earth's thin atmosphere is made mostly of hydrogen and helium, most of which is stripped by the solar wind, since the Earth hasn't yet formed a magnetic field. As a result, the young planet has little protection from the sun's cosmic rays, and the planet is a hotbed of radiation. Earth is also constantly being bombarded with asteroids and comets, which add to its mass, a process called accretion.
Just imagine a big ball of chewing gum that you keep adding to with fresh wads of gum, and you'll get the idea. So not only is the young Earth hot and gooey, it's also growing. But these are not the only impacts the planet has to contend with. In the recent past, there was a cataclysmic event in which a protoplanet collided with the Earth, resulting in the formation of our Moon.
If our alien visitors were to see Earth in this state, would they see its potential? I'm unsure I would at this stage. But despite these ominous beginnings, the seeds of change are taking root. Riding aboard these inbound asteroids is a special compound that will play a crucial role in Earth's history – water.
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Chapter 2: How did life evolve during Earth's formative years?
And boy, what a difference 1.9 billion years makes. The planet is now in its cryogenian period, at a time scientists call Snowball Earth. According to these models, Earth is completely frozen over. Think of the last Pleistocene Ice Age, only a lot colder. In fact, all of the Earth's surface and half of its total ocean water are frozen solid.
The Earth has become so cold that temperatures at the equator are similar to those in modern day Antarctica.
While the scientists aren't sure what triggered this downshift in global temperatures, some theories include a major volcanic eruption that spewed ash into the atmosphere, a vast reduction in greenhouse gases due to photosynthesizing lifeforms, and Milankovitch cycles, which we've previously covered on this channel.
Of course, it was quite likely a combination of factors that amplified this global cooling. Interestingly enough, underneath all this glacial ice is a single supercontinent called Panotia, centered on the South Pole. However, given the vast glacial cover, our alien visitors are having trouble discerning land from ocean. As a side note, don't confuse this supercontinent with Pangaea.
Plate tectonics will eventually break apart Panotia and reform that later supercontinent in a few hundred million years. But let's not get ahead of ourselves. Our space visitors land and wander around the vast, endless glaciers, amazed that this frozen landscape was once covered in molten rock.
At first, they think the harsh climate might have wiped out Earth's fledgling life, but that life has proven remarkably resilient. Cyanobacteria remain in the ocean, perhaps clustered around hot hydrothermal vents, much like the black smokers that are currently at the mid-Atlantic ridge. There are also newly evolved microbial lifeforms, such as red algae.
Complex, multicellular life remains elusive, but the fact that life has found a way to survive the planet's harshest freezing event so far is a testament to its staying power. At this point, I'd like to imagine our alien visitors having an argument among themselves. The youngest and most temperamental of the group is having a tantrum.
First a lava ball, then a barren bacterial playground, and now a ball of ice, it exclaims. Why do we keep coming back here? But the eldest of the group puts an arm, tentacle, or articulated limb of our preference around its younger comrade. Patience, the wise alien Taurus says to its impertinent partner. I have a feeling this planet is in for some major shakeups.
Let's come back in another few hundred million years. I think it will be worth the trip.
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Chapter 3: What caused the Snowball Earth phenomenon?
Temperatures will again plunge, setting off the late Paleozoic Ice Age before rebounding to warmer temperatures again. And complex life will continue evolving in remarkable ways. Among the new species will be amphibians and some giant reptiles you might have heard about called dinosaurs. I wonder when our alien scientists will visit next. How far in the future will they be? Will they meet us?
Will they exchange some intergalactic travel tips with our future descendants? I guess we'll have to leave that chapter of Earth's saga for another day. I hope you enjoyed this journey of planetary evolution. Are you interested in hearing some more about Earth's past in future episodes? If so, let me know in the comments. The Earth is 4.54 billion years old, plus or minus 50 million years.
That's a lot of birthdays. In that time, Earth has undergone some pretty incredible changes. In a recent episode, we covered 4.2 billion years of that history, which saw the Earth transform from a molten ball of lava, to a pale orange wasteland, to a giant snowball, to a flourishing tropical world.
But Earth Saga is like a TV drama that keeps taking twists and turns, with some of the most incredible stuff happening in the last 300 million years. So, for those of you that were disappointed we didn't cover dinosaurs in part 1, well, you might want to stick around. And for anyone just tuning in, here's our premise.
Imagine that alien scientists visited Earth at various stages in its development. What kind of planet would they find? I'm Alex McColgan and you're watching Astrum. Join me today as we continue Earth's saga and imagine how the planet might have looked in its ancient past. First, a reminder.
To answer these questions, we'll draw on models that not all scientists agree on, although the job gets easier when our timeline is in the millions rather than billions of years. Not all of the science is settled, and some of these models are still being debated, but to the best of our current knowledge, this is what our planet could have been like. Now, back to the story.
Our intrepid alien scientists are fresh off their exciting trip to Earth during the Devonian period, and are pretty excited about the direction things are headed. Obviously, they need to see what happens next, so they make a return trip 280 million years ago. Earth is now in its early Permian period.
The biggest geographical change is that the continents of Euramerica and Gondwana have combined into a single landmass called Pangaea. The collision of these continents, called the Viriskan Orogeny, unleashes powerful tectonic forces that create a mountain range called the Central Pangaean Mountains. How tall are they?
Well, Mount Everest is in the right ballpark, as this range is comparable in size to the modern Himalayas. In fact, they are so tall that they have a profound effect on the climate of Pangea. The central Pangean mountains lie just beneath the equatorial rainy belt. And our scientists quickly discover the impact of these giant mountains on the entire continent.
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Chapter 4: How did the Cambrian Explosion change life on Earth?
Believe it or not, the sail could be an adaptation that predates the transition from exotherms, or animals that absorb heat from their environment, to endotherms, which regulate temperature internally. You know, warm-blooded creatures like you and me.
Dimetrodon's sail contains a network of blood vessels, which allows it to raise its temperature more quickly in sunlight, an early step towards temperature regulation. On a planet experiencing all kinds of climactic changes, this ability to regulate temperature would certainly be advantageous. It's a wonderful illustration of how much living organisms can and must change in order to survive.
our planet's climate is like a complex system full of inputs with a biosphere as corresponding outputs. Planets like ours dictate what sort of life can exist on them, and interestingly, as a planet changes over time, the type of life it can support also changes. Impressed by Earth's development, our alien scientists decide to return in another 100 million years.
Unbeknownst to them, they will miss the largest extinction event in Earth's history, and I'm not talking about the asteroid that eventually killed off the dinosaurs. A much more catastrophic extinction takes place around 252 million years ago, called the Permian-Turassic extinction event.
Our leading theory is that volcanic eruptions release a huge amount of CO2 into the atmosphere, which raise global temperatures and make the oceans more acidic. This catastrophic event eradicates about 70% of terrestrial vertebrate species and 80% of all marine species, a mass die-off unmatched by any other in the history of the planet. Yet, as devastating as this is in the short term,
it would eventually clear the field for a whole lot of evolutionary diversification during the Jurassic and Jurassic. And chief among the beneficiaries is a group of reptiles that would one day rule the planet. Dinosaurs. Our alien scientists returned to Earth during the late Jurassic period, 150 million years ago.
Although Pangaea managed to hang around until the early Jurassic, by now it is starting to drift apart due to tectonic movements in the planet's lithosphere. The Earth is made up of about 15 to 20 tectonic plates, which are always moving toward or away from each other at a rate of around 1.5cm a year, which interestingly enough is pretty much the same rate as our toenails grow.
As plates move away from each other, they open a rift marked by outpouring basaltic lava. So, beginning around 200 million years ago, Laurasia breaks away from Gondwana, creating two smaller supercontinents. In the north, Laurasia contains modern-day North America and Eurasia. To the south, Gondwana includes modern-day South America, Africa, Australia, India and Antarctica.
A narrow body of water called the Tethys Sea is also opening up. It will one day grow into the North Atlantic Ocean, as outpouring basaltic lavas at the mid-Atlantic ridge continue to push the landmasses farther apart. Meanwhile, in the south, Antarctica and Madagascar have begun to separate from Africa, opening up the Proto-Indian Ocean.
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Chapter 5: What was the impact of the Permian-Triassic extinction event?
but that chapter will have to wait for a return trip by our intrepid travellers. They are worn out from the scrapes and scares of this trip, but they certainly have an idea of Earth's immense diversity and adaptability. Who knows, they may come back to finish the story another day.
Welcome back to our alien tour of Earth's history, where we reconstruct what prehistoric Earth might have looked like over millions and billions of years. For those just tuning in, our premise is this. Imagine that alien scientists are visiting Earth at various stages in its development. What do they see?
In part 1, our alien voyagers covered a big chunk of Earth's timeline, 4.2 billion years of it. They saw the formation of the planet, a hot, molten, swirling mess, its eventual cooling, the emergence of the first organisms, and the great oxidation event that gave Earth its modern atmosphere.
They swung by in the Cambrian period to witness an explosion of species diversity across our planet, and landed in the Devonian period some 350 million years ago. In part 2, our alien scientists came back to take a more in-depth look at some of the animals that roamed our then flourishing tropical Earth some 150 million years ago.
Supersaurus gave them a scare, while the furry little Tenialabis caught their eye with its playful and social disposition, while Archaeopteryx circled above. Today, they revisit Earth, some 84 million years later, totally oblivious to the changes that have occurred on this now dramatically different planet. I'm Alex McColgan and you're watching Astrum.
Join me today as we explore one of the most famous events of Earth's history, the dinosaur extinction. We'll examine the two leading theories of what caused this mass extinction and what kind of impact it had on the animals who were around to witness it.
For the last tens of millions of years, every time our alien friends flew over Earth, they'd seen a lush, green world run by the likes of Ceratosaurus, Barrosaurus, and Eoraptor. Let's imagine our alien explorers decide to descend and collect samples of this incredible world on a certain day 66 million years ago. But first, they need to make a pit stop.
They are running low on helium-3 and swing by Jupiter to fuel up. Without this source of power, their ship won't be able to take off again once they land on Earth. Tomorrow, they agree, they'll come back. When they return the next day, they double check their GPS, or Galactic Positioning System. They must have made a mistake.
There is no way the fireball covered in soot they are looking at is the same thriving planet they flew over yesterday. Our alien friends are flabbergasted. What could have happened to cause such utter devastation? The Earth they came back to is covered in raging wildfires, tsunamis up to 1km high, and immense, inescapable death.
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Chapter 6: How did dinosaurs come to dominate the Earth?
Meanwhile, trillions of metric tons of debris, about 60 times the mass of the asteroid, explodes up into the atmosphere. Some of this debris are chunks of molten earth crust, which, high in the atmosphere, coalesce into tektites. And inevitably, what goes up must come down. For about 15 minutes following the initial impact, Earth is covered in a torrential storm of fire rain.
Falling debris heats up to hundreds of degrees Celsius as it passes through Earth's atmosphere. This sets the world on fire, burning down 70% of its forests. Vaporized material that doesn't rain down as debris, such as silica dust from rocks, stays suspended in the atmosphere, along with unbelievable amounts of soot and carbon dioxide rising from the wildfires.
If you're breathing a sigh of relief for our Indonesian dinosaur friends on the other side of the planet, don't. Like with most things, it's never the actual impact that leads to the most devastation. It's the aftermath. The buildup of gases and particle debris in the atmosphere blocks out the sun, plunging the planet into an impact winter that will last at least 15 years.
With no sun, plants are unable to photosynthesize, and both terrestrial and marine food chains collapse. Earth is a totally apocalyptic version of its former glory. No wonder our alien travellers had to check their GPS. The impact this would have had on animals would have been devastating.
75% of all species are wiped out forever, making this one of the largest mass extinction events in Earth's history, second only to the Permian extinction we covered in part 2. All the animals that exist on Earth today are descendants of the survivors of this apocalypse. Others were not so lucky. Being large is a disadvantage in an apocalypse.
You need lots of food, lots of space, and lots of resources. All terrestrial and marine dinosaurs suffered greatly and eventually died out as a result. A small slither of avian dinosaurs had better luck and managed to slink through the evolutionary bottleneck into the Paleogene period. They still roam the Earth today through their direct descendants, birds. When we think of birds, we think beaks.
But back in the Cretaceous days, birds came in all kinds of different, wonderful variations that we've never seen with our own eyes. Some had beaks, some didn't. Some had teeth, some didn't. While it would be foolish to credit a single trait for the survival of an entire family line, it sure seems that if you were a bird 66 million years ago, having a beak stacked the odds in your favour.
We think that beaked birds had an advantage, as they could dig out seeds from the ground when no other food source was available. Toward the end of the Cretaceous, beaked birds were already eating a more varied diet than their non-beaked cousins. This would have been a huge advantage when rations were scarce. After all, being a picky eater in an apocalypse isn't really a good idea.
Having enough force in the gizzard to crush tough fruits and seeds, and enough light stamina to gather food over large distances also helped with survival. Some species of mammal also managed to push through. It is thought that only mammals smaller than 10cm survived, as they could hide underground where they were somewhat insulated from the lower global temperatures.
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Chapter 7: What role did Pangaea play in Earth's geological history?
I hope this exploration of possible theories is enough to satisfy our alien scientists. By now, they've seen Earth in enough of its forms to know that if there is one thing they can rely on, it's transience. Earth won't be a ball of fiery rain and eternal winter forever. It's just a matter of time before life springs up again. Who knows what they'll see on their next flyby. Thanks for watching.
I hope you enjoyed this third chapter of Earth's planetary evolution. Are you interested in learning more about Earth's history in future episodes? Which part of Earth's history would you like to visit if you could? Please let me know in the comments.
In the centre of the arid and ancient supercontinent Pangea, thousands of miles away from the sea, our time-travelling aliens have returned to witness a key moment in Earth's history. As they arrived, the rain began to fall. Just off Pangea's west coast, in what is now Canada, epoch-ending volcanic activity sent off a chain of events that all but made this downpour inevitable.
It would never look the same, because this was the start of a reign that wouldn't abate for over 1 million years. A reign that changed the course of life on Earth. A reign that allowed the dinosaurs to take over the world in an evolutionary coup.
What's all the more surprising to me, and to our aliens who witness life on Earth develop, is that the kind of event that caused this rain is, ordinarily, the most reliable and powerful extinction event the world has ever known. But this one was different. one that takes the butterfly effect to its limits.
Imagine, if a butterfly flapping its wings can cause a tornado 1,000 miles away, what does an eruption 100 times larger than a supervolcano cause? I'm Alex McColgan, and you're watching Astrum.
Join me today as we discover how an extinction-level event 230 million years ago increased the richness of life on Earth and accelerated the evolution of the dinosaurs, learning as we move through Earth's major cycles how burning fossil fuels contributed to climate change way ahead of the industrial revolution. What came before the rain?
Pangaea was the largest continent that has ever existed on Earth by a long way, a record not likely to ever be beaten given it was the size of every current continent combined. Its huge size meant that the centre was far removed from coastal climates and therefore received very little rain, favouring the evolution of species that required less water to survive.
During this dry period around 300 million years ago, in the Carboniferous period, several species emerged that are still important today, including dragonflies, millipedes, and spiders. Throughout this period, the diapsids also exploded, a group containing lizards and snakes as well as archosaurs. Now, you may not know that name, but you certainly know what this group contains.
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Chapter 8: How did early mammals adapt and evolve?
Specifically, the release and production of carbon dioxide and the release of stored methane. Eruptions like these directly release carbon dioxide already contained within the mantle, but they can trigger its release from other stores too. from a source of carbon I thought only humans had used. Huge reservoirs of fossil fuels.
Now, whether you remember the fire triangle from school or not, fuel, heat and oxygen, I think we can all appreciate that introducing 1600°C magma to the base of untapped virgin coal beds is going to get spicy. Burning these crude coal beds would have released incredible amounts of particulates and greenhouse gases, both important for driving cloud formation and rainfall.
Just as we are seeing today, the increasing levels of those greenhouse gases trap more of the sun's energy, and that energy has to go somewhere. So where does it go? Earth systems work to distribute that energy, and the one best place to absorb this extra energy is the water cycle, which becomes supercharged. The sun's energy is absorbed by the land and sea, evaporating water from the surface.
Once in the atmosphere, the water can be carried great distances before precipitating onto land and returning to the sea along a meandering route. The more energy that is trapped by greenhouse gases, the faster the water cycle turns over. In these flood basalt eruptions, we see an extreme example of the complex interplay of the three major cycles, the geological, carbon and water cycle.
The formation of the Rangilian large igneous province would have released huge amounts of CO2. Our alien ship detected atmospheric levels exceeding 1,000 parts per million, 2.5 times what they are today, increasing temperatures by 3-4 degrees Celsius.
This supercharged the water cycle, greatly increasing evaporation and cloud formation, and these clouds were increasingly able to deliver rain further and further into the centre of Pangaea. Throughout this period, the Earth became warmer and more humid, a dramatic change in the climate.
Species that had adapted to a particular dry climate environment or niche before the rain were put under stress from multiple fronts. During this turnover period in Earth's history, our aliens watched as old niches were seemingly destroyed as quickly as the new ones were created. The status quo was changing. Not only that, but species had to cope with a pH shift too.
Carbon dioxide wasn't the only gas released by the Rangilian eruption. Hydrogen sulphide gas erupted into the atmosphere along with it. This egg-smelling gas reacted with oxygen and water to form sulfuric acid, which in this form is more well known as acid rain.
As the rain fell, the soils and oceans became inundated with acidified water, which only further contributed to the environmental stress some species were facing. Interestingly, a large amount of amber can be found in the geological record from the
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