A new explanation for the reasons for the Great Permian Extinction is the combustion of coal in magma. This news reminds us of how little we know about the greatest catastrophe in the history of earthly life. Traditionally, it is explained by volcanic eruptions and overheating of the planet. However, a number of evidence points to the opposite scenario - the death of most species due to a sharp cold snap. Oddly enough, this question is not at all academic - it also determines how we respond to global threats today.
We recently published news that coal burning in Siberia was a possible cause of the Great Extinction. Different scientific groups have different views on the causes of certain events. The authors of the new work in the journal Geology are supporters of the view that the largest extinction in history was due to warming.
However, we considered it necessary to draw the reader's attention to a fundamentally different, opposite point of view - formulated in an article from Scientific Reports from 2017.
Below we will show that we consider the second point of view closer to the truth, not just because it was published in a more prestigious scientific journal, but because it is less in conflict with all the scientific data accumulated to date about the greatest tragedy in the history of earthly life. So to the point.
In sediments dating back about 251.9 million years ago, a very unusual phenomenon is noticeable around the world - the almost complete disappearance of any organic remains. From finds of traces of animals and plants to commonplace coal. Such "empty" layers mean extinction, and after 251.9 million years ago comes the thickest "empty" layer in history.
When a more "living" layer comes in its place, more than 90% of all marine species and more than 70% of all terrestrial species - those that existed before the "empty" layer no longer occur in it. Even more than 80% of insect species - usually the most resistant to various kinds of disasters - have become extinct.
This titanic event in its scope is called the Perm extinction, and in the English-speaking world it is often called the “Great Extinction”. Against this background, even the death of dinosaurs 66 million years ago seems to be something relatively easy and non-destructive.
An extraordinary event must be matched by extraordinary reasons. The extinction time mineral calcite shows that the concentration of CO2 in the atmosphere then jumped to 2,000 parts per million - almost five times higher than today. In addition, geologists have discovered that Siberian traps poured out at that time. Their volume is not less than a million cubic kilometers. That is, for the formation of this pile of rocks, an outpouring of quadrillion tons of lava was required.
There are no other traps in the world of the same size. Accordingly, the largest series of volcanic eruptions occurred about 252 million years ago in the history of the Earth. Moreover, a high content of CO2 was established. From this, several scientific groups at once made what seemed the only possible conclusion: volcanoes are to blame for the Great Extinction. They emitted a record amount of carbon dioxide into the atmosphere. He overheated the Earth (by about eight degrees) and destroyed almost all large species of living things on it.
And now, as we already wrote, now another logical touch has been added to this hypothesis. As stated in the relevant news, it turned out that in the lava, which rose upward with eruptions, there was a lot of partially burnt coal. Powerful eruptions literally turned the coal seams outward, the coal burned, its ash rose high into the air and reached at least Canada.
The authors of the work describing this (among them there is a scientist from Moscow State University) draw unambiguous parallels between the Permian extinction and the present. Like today, then a huge amount of fossil fuels were burned, and after that acid rain should have come (sulfur impurities in coal give sulfur dioxide). The destruction of the ozone layer that happened in a distant era is also mentioned.
The lead author of the article even argues, "With this kind of similarity, we need to make extra efforts to act now" - that is, to combat phenomena such as massive fuel combustion.
It turns out that the developed biosphere of the Permian period mainly perished due to the fact that the Earth plunged into the flames of coal fires and volcanic lava spills? As we will show below, not everything is so simple.
What cools in our era, warmed up in that era?
The first thing that attracts attention in the scenario "volcanoes are to blame for everything" is that today no eruption leads to warming. After the eruption of Pinatubo in the 1990s, the planet's temperature dropped. After the eruption of Krakatoa and Tambora in the 19th century, too. Moreover, from the latter the cold snap was so strong that in Europe there was a crop failure from the cold. The explosion of the Huaynaputin volcano at the beginning of the 17th century led to the fact that in central Russia, crops perished for three consecutive summers. Famine killed a significant part of the country's population.
The physical mechanism is very clear here. During the eruption, volcanic ash and sulfur dioxide enter the stratosphere. Both effectively absorb solar radiation during the day, and when cooled at night, it easily transfers the received heat back into space. The troposphere, from which heat is lost much less, cools down.
How did it happen that 251.9 million years ago everything was completely different? Why volcanoes, always leading to a cold snap, suddenly led to warming just this time?
The final piece of this puzzle is ultraviolet light. A number of extinct fossil spores do not have a normal separation and are found in clumps of four. This happens if the development of a plant is disturbed by high ultraviolet B (wavelength - 280-315 nanometers). This means, supporters of the traditional scenario say, the ozone layer has been destroyed. This makes sense: volcanic emissions contain a number of compounds that actually destroy ozone molecules.
But above we said that volcanoes, erupting, emit a lot of sulfur dioxide. One of the absorption peaks (this is the name of the part of the electromagnetic spectrum that this substance absorbs best) falls on ultraviolet B. Moreover, if there is only three billion tons of ozone in the atmosphere, much more sulfur dioxide can be released during lava eruptions, and it settles he's out of the stratosphere rather slowly. Where did the excess of ultraviolet radiation come from on Earth at that time?
Why, with warming, most species survived in the tropics
The second mystery of the volcanic scenario is visible in the illustration above. The outpouring of lava and coal burning happened in Siberia, which is in the Northern Hemisphere. Meanwhile, marine species suffered the least in the tropics of the Northern Hemisphere: significantly fewer species survived in the southern tropics. Why is this so?
Volcanic eruptions of the same magnitude as in the Permian period produce many halogens (for example, chlorine, iodine and bromine), which not only destroy ozone, but also directly poison living things. Why was extinction weaker closer to Siberia, in the Northern Hemisphere?
Even stranger is the fact that the least marine species survived near the poles. Yes, there the water temperature rose the most - by 15 degrees, and in the tropics only by 10-12. But the fact is that at the poles the initial temperature of the seas was several degrees lower than in tropical waters. That is, the absolute values of temperatures there were still no higher than in the tropics.
According to the modern rapid shift of thermophilic marine species to the poles (by six kilometers per year), we know that living things during global warming are capable of migrating to warming zones in a matter of decades. In theory, if the Permian extinction was caused by soaring temperatures, tropical species should have rushed north and south. Why are most of the surviving species instead visible in the tropics and not in the north?
Why a surge in CO2 and warming in general could lead to extinction
The third problem in the volcanic theory of extinction is CO2 concentration. There is not a single scientific work that would confidently assert that in the era of the Permian extinction, carbon dioxide in the air was significantly higher than 2000-3000 parts per million. Meanwhile, it is reliably known that about 55 million years ago, during the Paleocene-Eocene temperature maximum, the concentration of CO2 was definitely not lower than these values.
The average temperature on the planet then also rose by eight degrees (to an average of 23 ° C) - it rose to about the same level (~ 24 ° C) at the end of the Permian period.
However, there was no extinction in the Paleocene-Eocene maximum. In fact, everything was the other way around: the number of new species found in geological deposits has increased dramatically. The reasons for this are clear: the more CO2 in the atmosphere, the more intensively the plants grow, the greater their biomass. Animals feed on plants, which is why their biomass also increases.
Moreover, with really high CO2, there are no deserts on Earth. Because warming increases evaporation from the oceans, which results in more rainfall, and a high concentration of carbon dioxide allows plants to less open the stomata of leaves for respiration. From this, less moisture leaves through the stomata - and the need for vegetation for it decreases. There is no evidence at all that there were deserts on the planet in the Paleocene-Eocene maximum.
Why did the warming nowhere, except for the Permian extinction, lead to the mass extinction of species?
Warming or cooling: a question of dating
In 2017, Scientific Reports published a very interesting article. A group of Swiss scientists using the material of Chinese fossil rocks found out: in reality, the loss of traces of complex life from the sediments did not happen 251.9 million years ago, but several tens of thousands of years earlier.
It would seem that tens of thousands of years change against the background of hundreds of millions? Oddly enough, everyone. The fact is that at the moment obtained by the new dating, the sea did not come - as 251, 9 million years ago, as it happens during strong warming - but receded.
The sea has no drain hole: it can only recede in one case. And this case is a cold snap leading to the formation of glaciers. It turns out that the extinction did not occur during an increase in temperatures, but during a decrease.
"The generally accepted statement that the Permian mass extinction occurred" during the sea level rise … "cannot be defended in light of our dating," summed up the Swiss in 2017.
Over the past three years since then, no one even tried to refute their dating. This is understandable: the authors used geological samples from many areas and used a very reliable uranium-lead method for establishing the date of the sample.
Let's mentally return to the beginning of our text. The question arises: why did the authors of the new work in Geology not take into account the results of the earlier article in Scientific Reports or, if they consider it incorrect, did not dispute?
The reasons can be of two types. First, modern scientists are often so trapped in their specialization bubble that they don't really read articles that seem irrelevant to their interests.
Secondly, if the work of one scientific group contradicts the work of another scientific group and at the same time it is difficult to criticize it, then often the second scientific group simply does not mention the work of the first one in its analysis. This, unfortunately, is also common: it is enough to recall at least the authors who are still writing about the mega-impact hypothesis of the formation of the Moon.
An entirely different general picture of events follows from the earlier date of extinction. Initially, it became colder, the sea receded, organic remains became very rare (extinction). Then, as the authors write, "carbon dioxide from the Siberian traps and the coal burnt there provided a gradual warming and advancing sea." But it was no longer the cause of extinction: after it, the amount of organic precipitation does not show a decrease.
The new date of the death of a living person significantly clarifies the three problems that we indicated above. Indeed, one should not be surprised why nowadays volcanic eruptions lead to a cooling, and then led to warming. It turns out that about 252 million years ago, volcanic eruptions made the world colder with their emissions, which killed many species.
It is not surprising why most of all species have survived in the tropics. When species die from lower temperatures, it is easiest to survive where the warmest is. The question of why warming usually does not lead to extinction, and then led: it turns out, and then did not lead, is also removed by itself.
During the period of volcanic eruptions after extinction due to cold snaps on the Earth, there should have been such a shortage of life that there was no one especially to bind CO2, turning it into biomass. This contributed to the further accumulation of carbon dioxide in the atmosphere - up to very high values - and a gradual warming, even in spite of the emission of sulfur dioxide.
But, unfortunately, having resolved these issues, the Swiss dating left others.
So what killed the Permian biosphere
We now know how the Greatest Extinction (another English name for the event) happened. There is a classic picture: lower temperatures, more difficult to feed, more difficult to survive.
But there is still more incomprehensible things. From the available data, it is very difficult to understand exactly how much the temperature dropped. But it is obvious that it is stronger than with the extinction of dinosaurs: after all, then, 66 million years ago, more than 80% of insect species did not become extinct. Since the Permian extinction is stronger than all the others, then the cooling during it should have been a record one.
It is extremely difficult to imagine only a volcanic scenario of such a strong and rapid cooling. Volcanic activity on Earth is already billions of years old, but there is no evidence that it suddenly took and caused an extremely rapid decrease in temperatures necessary for a mass extinction, for any other epoch is not observed.
There are reasons for this: any volcanic eruption is stretched out in time. Plus, in addition to cooling the planet with sulfur dioxide and ash, volcanoes simultaneously emit a lot of carbon dioxide, which, on the contrary, warms the planet. This means that it is quite difficult to destroy species en masse by volcanic cooling.
And again it remains unclear why the eruptions were in the Northern Hemisphere, and the extinction of species was stronger in the Southern. The air is most saturated with volcanic ash in the hemisphere where it erupts. At that time, no volcanic traps were formed in the Southern Hemisphere. Obviously, the extinction was due to a cold snap, but why then it was stronger far from the cause of this cold snap?
The answer is under the ice of Antarctica?
At the beginning of the 21st century, radars and gravimetric measurements confirmed the existence of a very strange formation under Wilkes Earth (Antarctica). It is an anomalous concentration of dense rocks about 300 kilometers in diameter, located inside a crater with a diameter of 480 kilometers.
Of course, the anomalous concentration of dense rocks does not mean that the asteroid itself was 300 kilometers in diameter. It was clearly noticeably smaller, hardly more than 20 kilometers. But that was too much.
To understand what we are talking about, let us recall: the Chicxulub crater, left by a ten-kilometer asteroid 66 million years ago off the coast of Yucatan (now Mexico), has a diameter of only 180 kilometers. That is, the "funnel" from what formed the crater of Wilkes' Land is 2.66 times larger than from what killed the dinosaurs (more precisely, as we already wrote, part of the dinosaurs, thousands of their species still live around us).
The Antarctic ice crater is difficult to explore: there is more than a kilometer of ice above it. Therefore, his exact age is unknown. We can only say that it is not older than 500 million years, because otherwise plate tectonics would have already eliminated the anomalous concentration of dense rocks left by the asteroid.
Then it's easy to use logic. If the Chicxulub crater is 2, 66 times smaller, but the event that formed it led to a mass extinction and renewal of the biosphere, then the Wilkes Land crater should have given a much larger extinction than at the end of the dinosaur era. However, over the past 500 million years, there has been only one extinction, clearly superior to the Cretaceous-Paleogene (66 million years ago). And this is the only "super-extinction" - it is Perm.
The conclusion suggests itself that it was the asteroid that left the crater of Wilkes Land that led to a sharp cold snap that killed all large animals of that time.
The eruption of the Siberian Traps, unique in its scope, could also have been caused by it. A number of scientists support the theory that strong asteroid impacts should produce a convergence of shock waves at a point lying on the opposite side of the Earth. 252 million years ago, the point where the Wilkes Land crater is located was opposite the outpouring of the Siberian traps.
It turns out that there is nothing anomalous in the largest series of volcanic eruptions in the known history of the planet. What percussion instrument - such a trace from it. A record large impact crater must correspond to a record large lava eruption zone.
The asteroid explanation of the Permian extinction simplifies the answer to the question "why did the most species survive in the northern tropics?" The asteroid struck in very low latitudes of the Southern Hemisphere, that is, its effect on the Northern Hemisphere could be noticeably smaller.
So far, there is only one noticeable problem of the asteroid explanation: in order to confirm it finally, it is necessary to investigate the crater itself or find traces of material ejected by it in the rest of Antarctica. But both the crater and the continent are covered with kilometers of ice, which makes it very difficult to find "material evidence from the crime scene" here.
You can look for traces of discarded material in the Transantarctic Mountains, which rise above the ice.
But there is a nuance: it is very difficult to explore the mountains on this continent. It's cold there, and sending expeditions is expensive. Yes, and these mountains themselves have experienced a strong rise in the last hundred million years, and how much intact layers of the times of the Permian extinction were preserved there is not always clear.
In the meantime, it remains only to state that the asteroid version of the catastrophe contradicts the facts known to science to the least extent. It explains both the cooling, inevitable due to the asteroid winter, and the Siberian traps, and the relatively weak extinction in the northern tropical seas.
She also removes the question of the reasons for the uniqueness of the Perm catastrophe. If it was caused by ordinary earth volcanism, it could not fail to repeat itself: volcanoes on Earth erupt in all epochs. But if the matter is in an asteroid that left a crater half a thousand kilometers away, then the Great Extinction should naturally be the largest. After all, the asteroid that caused it was bound to be the largest that hit the Earth in the foreseeable past.
What follows from this
On the one hand, the asteroid explanation of the Permian catastrophe sounds reassuring. It turns out that on Earth - without a push from the outside - such a series of volcanic eruptions cannot begin that will put an end to the existing complex life. And there is no need to worry about the fact that global warming will destroy all of us.
That was the end of the comforting news. The very fact that the planet can be hit by a body forming a funnel with a diameter of 480 kilometers means that humanity is still noticeably underestimating the asteroid threat. Of course, such a large asteroid that created the Wilkes Land crater cannot fall on its head unexpectedly: it will be visible to astronomers in advance.
But is it enough in advance to have time to prevent its collision with the Earth? Especially if he is an interstellar traveler like the Borisov comet - one whose appearance near our planet can be predicted only a few months before the collision.