The Huronian Period When The Earth Was Completely Frozen Over For 300 Million Years

When we say the term Ice Age, what comes to mind? For many, it will most likely be the classic image of mammoths and wooly rhinos wandering through the boreal forests and glaciers of the Pleistocene, a time when Homo sapiens were competing with Homo neanderthalensis out on the wide open steppes. You might be surprised, if this is the case, to learn that there have actually been five major Ice Ages throughout the course of Earth's history. From most recent to least recent, these have been the Quaternary Ice Age, where mammoths and early humans came in, the late Paleozoic Ice Age at the end of the Devonian, the Andean-Saharan glaciation at the end of the Ordovician, the Cryogenian just before complex life evolved, and right back in the depths of time, the Huronian. The latter is the subject of today's video, which took place a staggering two and a half billion years ago. Today, we will be taking a look at what the world was like during this very, very early Ice Age, discussing what brought about the changes and how the world would eventually warm up. This is by far the furthest back we have gone in any of our videos, so sit back and relax as we explore deep time to understand the Huronian, the world's first major Ice Age. Before we explore the timeline of the Huronian, let's stop and take a look at what defines an Ice Age. Technically, we are living in one now. We are in a warm interglacial period, which started about 11,000 years ago off the back of the Quaternary Ice Age. Ironically, the Ice Age that brought about the rise and fall of the mammoths has not ended, despite all of our man-made greenhouse gases and global warming. Scientifically speaking, an Ice Age is an extended period of declining temperature on the surface of our planet. These changes in temperature cause the widespread appearance of polar ice sheets. The colder the world gets, the more prominent these become. In mountainous regions, Ice Ages cause glaciers to appear, which can recede and grow with the changes in temperature which take place throughout the course of Ice Ages. Ice Ages throughout the course of prehistory have vastly altered the appearance and climate of the planet, bringing about new ecosystems and directly impacting the disappearance and fluctuation of organisms. The Cryogenian Ice Age, for example, has previously been considered to be responsible for the rise of multi-celled life as we know it, as relatively shortly after its decline, the Cambrian Explosion happened. This was the first time large, complex animals appeared on the planet, which may have been partially caused by the warming of the waters in which these early invertebrates evolved. This is controversial to some, however. The most recent Ice Age brought about the perfect conditions for megafaunal mammals, some of the largest to ever walk the Earth to evolve. To the icy north lived mammoths, woolly rhinoceroses, ground sloths, and mastodons, all of which came into contact with humans. In some circumstances, such as the Ice Age that took place in the Late Devonian, it was the organisms that brought about the onset of the Ice Age, with land plants bringing excess oxygen to the atmosphere, which would ultimately cause cooling. Ice Ages can be brought about in different ways, and have a multitude of effects and consequences. Firstly, it is important to note that the Huronian was not one single glaciation, but rather several intense ones that made up a few huge Ice Ages, lasting from about 2.4 billion to 2.1 billion years ago. This makes the Huronian the single longest period of continuous Ice Ages in Earth's history. But it is difficult to calculate the specific figures and dates due to the fact that this took place a staggeringly long time ago. Consider that the dinosaurs only appeared on the scene around 230 million years ago. This Ice Age began over 2 billion years ago. That is a truly colossal amount of time, and the rocks can only tell scientists so much when they're this old. As a result, much of what we know about the Huronian is based on estimations calculated from sparse evidence. The Huronian Ice Age first began in what is known as the Paleoproterozoic Era. At this time, Earth was about half the age it is now, and as you can imagine, it would have been unrecognizable if you were to see it today. The center of the Earth was much warmer than it is in the modern day, thanks to the presence of high numbers of radioactive isotopes which produce heat as they decay. This heat was reciprocated on the surface, as the heat slowly dissipated outwards towards the crust and exterior of the planet. High levels of methane and carbon dioxide were present in the atmosphere, making this strange, near-alien world an inhospitable, toxic hothouse. Plants were still billions of years from evolving, only appearing on the scene 700 million years ago, creating a barren, rocky supercontinent known as Columbia, which was cloaked in red-hot seas of up to 85 degrees Celsius. Life did exist here, but not as we know it. The largest organisms on Earth were visible only through a microscope. Multicell life had recently begun to evolve, but we were a very, very long way off from meeting the world's first advanced animals. What's more is that the Earth's rotation was much different in the Paleoproterozoic Era, meaning that one year lasted 450 days, with each day lasting just 20 hours long. The Huronian Ice Age began as a result of changes in the atmosphere that created the right conditions for a freezing world. The first change was a noticeable drop in methane gas in the air, which coincided with a steady increase in oxygen levels. These changes were brought about by an increase in cyanobacteria in the waters, which in turn displaced the methane and made the conditions right for a cold world. The increase in oxygen at this time is indicated by the presence of banded iron formations, colored red in a mesmerizing pattern by hematite. These patterns are not found in older rocks, which point to these changes in atmospheric conditions being a key factor in the onset of the Huronian. The repeating glaciated periods across the course of the Huronian were brought about by changes in the atmosphere over the course of the Ice Ages. Lower oxygen levels resulted in more warming, whereas more oxygen cooled the planet down again. While we are currently living in an Ice Age, it is certainly not the Huronian. Earth today has two ice sheets, a huge one in Greenland and an even larger one that covers Antarctica. In the Huronian, the entire world was blanketed in one, creating a massive sphere of frost, snow, and ice suspended in space. To a distant observer, the planet would have literally been a white sphere, with a few mountainous and ocean regions left exposed. This is so different to the modern day and so deeply back in time that it's quite hard to imagine. It surely would have been one of the most hostile habitats our planet has ever seen. For 250 million years following the beginning of the Huronian, Earth's volcanic activity all but came to a halt, providing the ice with even lower temperatures to creep across the globe. Greenhouse effects came to a standstill, and with very little carbon dioxide in the atmosphere, there was no end in sight for literal millennia. Despite the cold, life on Earth persisted. Granted, the organisms in question were adaptable, microscopic, thread-like beings. But with the conditions as harsh as they were, it's a wonder they were able to survive at all, let alone come out the other side on the verge of diversifying into much more complex beings. Their world had gone from not far off boiling to not far off freezing in a significantly short period of time, which is certainly a testament to the capabilities of these little organisms. Conditions on land were just as brutal. Colossal glaciers stretched out from high altitudes to low altitudes, creeping across the land like an inconceivably huge white cloak. These glaciers would cover entire swaths of the supercontinent before reaching the great ocean at multiple points, then beginning to freeze over its surface. If humans could travel back in time and see what the world was like in the Huronian, they would not last long. The dark skies were racked with snowstorms and barrages of freezing winds, making it one of the most blisteringly painful places to be anywhere in Earth's history. The Earth is constantly changing, and it would not be long, geologically speaking, until the ice melted, returning the planet to its former scorching glory. The snowball effect could only last as long as the atmospheric conditions permitted it to, and when they inevitably changed, the Huronian came to a watery end. The sheer depths of time in which this took place makes it very hard for scientists to determine exactly what brought about the end of the Huronian. But it is thought to have occurred when carbon dioxide began to steadily creep back into the atmosphere and stay there. This might have happened when volcanoes began to spring back into action on the face of the icy Earth, warming the surrounding area and launching the gas into the air in great quantities. Strings of eruptions could have worsened this effect, speeding up the intense global warming. These warmer conditions would persist for over a billion and a half years, until eventually the ice would return. The Cryogenian Ice Age brought the cold conditions back just before large and more complex animals began to evolve in the seas. This would potentially be the coldest Earth has ever been, and this Ice Age lasted over 100 million years, making it a close contender for the second longest glacial period our planet has experienced. From there life would continue to adapt and evolve into new and wondrous forms throughout the course of the Paleozoic Era, up until the end of the Ordovician, when the ice would return once more. The Huronian and the subsequent prehistoric Ice Ages the world has experienced make you wonder how humans can adapt and cope in the face of drastic climate changes to the planet in the modern day. It is interesting to think about how we would cope with another snowball Earth, but what might happen if our industrial assault on the planet continues without restraint? Extreme temperatures can be threatening in both circumstances, and our planet is a massively powerful force. There really is no telling what could happen to us if either of these scenarios was to take place. For now, however, we continue to press forward, still in our Ice Age, standing on continents that were once blanketed in thick, freezing ice. Given another billion years or two, what might our surroundings look like?