Guest post from Tallis
Some of the most beautiful of sights on the planet are the remnants of the most violent of scenes; The amazing Yellowstone National park is in place of the world’s most notorious “Super volcano”. As a rational conspiracy theorist, I have to constantly put up with the claims of Yellowstone’s imminent eruptions. This is probably why I am currently seeing a therapist as such ignorance can cause madness to the most calm of men.
It is silly to think that we would not notice 100 meter uplift before a caldera forming eruption or the gateway to hell opening before a flood basalt. The monitoring of certain volcanoes leaves a lot to be desired but some things are impossible to miss. I don’t want to get my science and my conspiracy mixed up but if the government can barely keep information of their more unfavorable actions secret then I don’t really think they can hide modern society coming to an abrupt end.
Flood Basalts and VEI 8 eruptions are the new disaster craze and arguably the most perfect for cheap headlines. After all unlike an impact event or an alien threat, we know that these eruptions are going to happen in the future and can track their unrest easily but still don’t know exactly when or where it will happen, and unlike Super bugs or ecological devastation, it is not an immediate concern or as scary in the short term. One thing is certain however if either of the eruptions were to start happening in the next 50 years we would know.
Basalt and Rhyolite are the primary ingredients of some of most awe-inspiring eruptions that this planet has ever seen. The viscous rhyolite produces large explosive eruptions while the fluid basalt produces rivers of molten rock. Everything intermediate magma does, these two do better and a great deal better at that. The worst our planet can produce is something that no one truly understands to the fullest. Scientists can’t even agree on the climate affects of the Samalas eruption so the effects of a larger VEI 8 eruptions are not settled.
Quantum mechanics are completely different from Classical mechanics, small scale motion is almost nothing like large scale motion but the laws of science are still not broken. It is a fact that something as simple as motion can be incredibly hard to understand and harder still to explain on certain scales. Volcanic eruptions, while not as complex, follows the same rules. After all you can’t compare a massive VEI 8 explosion with a Vulcanian puff, either in process or scale.
The process of caldera forming eruptions are a very long and somewhat tedious process despite scientists recently discovering that large eruptions can happen in a few decades. So many different factors play a role in large caldera forming eruptions, such as regional faulting, the pressure in the chamber, the strength of the rock, and possibly the hydrothermal system. I will explain how each factor plays a role in these massive eruptions. I would also like to say, once again, that I am not a volcanologist or scientist, I am just a person who loves volcanoes and has read up on a lot of research papers.
The pressure of the magma chamber is the most obvious and necessary component of any large explosive eruption. Magma chambers in “Super volcanoes” are usually cool and not very active with some chambers only having 5-10% melt, the magmas from the chamber stay there thousands of years and evolve into silica rich magma. The portions of melt in the chamber would likely make a very slow ascent to the top and the lack of massive pressure would aid in that. Isolated high concentrations of melt in a large chamber is what likely leads to the smaller cinder cone forming eruptions in large calderas. These pockets of melt are likely generated by smaller intrusions, the melt generated from an intrusion can stay molten for an elevated time in chamber after the intrusion ends. It probably doesn’t take much to destabilize the chamber to the point of a smaller eruption.
The pressure generated by unrest, past or present, puts cumulative stress on the roof of the magma chamber. The effects of past unrest on the rock containing the magma fades after some time but in very active calderas, the effects are sustained for a longer period of time. Earthquakes and uplift put stress on the on the rock above leading to cracks and weakening any plug the volcano has over a period of thousands of years. The smaller eruptions in these calderas either increase or decrease the chance for a caldera forming eruptions. Smaller explosive eruptions can weaken the crust holding back the eruption as well as plug some vents while effusive eruption removes the vital pressure and eruptible magma while eventually being part of the same rock that is keeping the magma chamber under control. This phase will take thousand of years before the massive eruption and is the most benign sign but this is an important part of the phase of Super eruptions.
The bulk of the pressure that is essential to the large caldera forming eruption likely comes from the heat and gas of the reactivated chamber. This what causes the period of unrest before the eruption but it still not enough. The accumulation of buoyant magma leads to the most severe period restlessness during the build up phase. The pressure from the accumulated magma sets the stage for a large eruption, making the system more susceptible to external variables. The actual size of the eruption however depends on how much eruptible magma accumulated to the top and the strength of the crust.
Hydro-thermal systems within large systems are a source for steam explosions. These are a threat that is independent of the system. However before a caldera-forming eruption the heat, earthquakes, and uplift from the unrest would lead to more explosions and unlike the magmatic eruptions, the activity would be more pervasive and widespread. The hydro-thermal reservoirs would lose a great deal of volume through massive steam explosions and this would be the smoking gun even from unmonitored systems. The explosions would not be enough to be the tipping point and is not a crucial factor as some systems don’t have a large hydro-thermal systems yet still have relatively frequent large eruptions.
Resurgent domes are an easy feature to spot and are perfect for scary headlines but are not a sign of an eruption. The greatest hazard from resurgent domes before a caldera-forming eruption are landslides. Some resurgent domes are of such size that if a large landslide took place during a period of severe unrest, it could destabilize the volcanic system and trigger a large explosion. The evidence for such slide could be buried.
Regional faults covering magma systems are greatly influenced by the state of the systems. The pressure and the size of the chamber puts stress on the faults which leads to larger tectonic earthquakes, which does little to affect the system during dormancy but during large scale unrest, this likely acts as the tipping point.
The elasticity and overall strength of the rock above the systems decides the scale of eruption. For brittle and weak rock, It is going to crack under the pressure much easier and for stronger elastic rock, even the most severe unrest may not produce an eruption without an external variable. If we would like to see where is most likely place we are going to find a “Super eruption” then we should study the roof of large magma chambers. This maybe a bit more hypothetical but I believe that volcanoes that have frequent large eruptions have weaker roofs to the magma chamber (Taupo is a possible example of this) and volcanoes that have frequent effusive eruptions have stronger roofs (Yellowstone).
The direct effects from a VEI 8 eruption is one of the rare cases where Hollywood movies don’t actually show the truly terrifying scale of such an eruption. Let’s say that Toba realizes that it didn’t finish the job 75,000 years ago and erupts again. The explosions would dwarf Krakatoa’s 200 megaton puff and the ash cloud would be larger than the largest countries. Pyroclastic flows would ravage the entire island and make the entire Indian ocean inaccessible by boat and ground flight worldwide. This eruption could inject sulphur and fine ash to the mesosphere, which could lead a more significant climate effect. Global temperatures would drop and there would significant global dimming. Thank goodness this doesn’t happen often. Some of gas rich fine ash would devastate the agriculture and poison freshwater over a continent. Some areas would be unreachable for years and whether or not an event like this could kill all of humanity, it would erase all of modern society while it sending human advancement back thousands of years.
Naturally an event like this would receive plenty of warning and not sneak up on us somehow and there is no system on that earth that is likely to produce such a large eruption in the near future. Just because these systems can produce large eruptions rather quickly doesn’t meant that the chances have suddenly gone up. It isn’t impossible for it to happen in the near future, we really don’t know if it will. So what? What is humanity actually going to do if it does happen? There are some disasters that you can prepare for and mitigate but this isn’t one of them and there is nothing anyone could do if it were to happen.
The fish canyon tuff is more than 5,000 km3 of ash and the eruption took place 28 million years ago and some material likely deteriorated, not only that the finer ash from the eruption is a significant percentage of the material emitted. Eruptions like this could very well be larger then some modern calculation shows.
When you scale disasters, people’s imagination immediately goes to what lies beyond the scale. Just google “F6 tornadoes.” and you will see how much that peaks people’s interest. A VEI 9 eruption captures the imagination of some and is a mysterious proposition. Most won’t deny that it is a possibility within Earth’s long history but there is no evidence of such events, an event like that would be rare and if it did happen in the distant past then the evidence leftover would not reflect the size of the eruption. A VEI 9 while entrancing is something that is only a conjecture.
Effusive eruptions are not respected in the slightest among the public but are the deadliest and most simple form of eruption. Flood basalts are so large that it difficult to comprehend their scale. Some of the largest flood basalts hold so much lava that you could cover the entire planet’s surface with at least 2 meters of lava. Such massive eruptions have been linked to the biggest extinction events but some of the biggest flood basalts did not cause any large extinction events. Why?
In order to understand why, we should break down how flood basalt happen in the first place. Flood basalts are generally cause by the break up of continental plates, a hotspot, or a mantle plume. It is even possible that some events are composite in origin. Flood basalt form large igneous provinces and are not a single eruption, they are multiple large volume eruptions and lasts for millions of years. You could argue that Hawaii is a small igneous province as Mauna Loa holds more than 40,000 cubic km and the hotspot is still strengthening. The hotspot delivers the bulk of its magma to one volcano. The Iceland hotspot is responsible for some of the largest effusive eruptions in history and has multiple volcanoes that are very dangerous, erupting explosively and effusively. Both systems could be a flood basalt in the distant future but are completely different.
A system that erupts a 1 cubic km of magma a year is not going to kill 75% of all life. The CO2 released is going to go through weakly damaged vegetation and would not last long enough through the eruptions to have a massive extinction event. In order to cause extinction, the event must be intense. The size of the flood basalt is not as important as some would think. The formation of largest igneous province did not cause an extinction event while the Siberian traps almost ended life on the Earth despite not even the second largest province. The Deccan traps likely played significant role in the Cretaceous–Paleogene extinction, the Central Atlantic flood basalt for the Triassic-Jurassic extinction, and the Siberian traps for the biggest extinction event in the Permian era.
I don’t believe that the global climate changes alone are responsible for the mass extinctions, Global cooling and warming happen with all flood basalts and only a few cause mass extinctions. The climate changes have to compounded with something else related with the eruptions. The Central Atlantic flood basalt event likely caused more significant global warming than cooling. The rate of magma expulsion was not enough to cause large scale cooling but it was enough to dump massive amounts of CO2 over a short period of time. This is just a theory and unlike the other two it is not as solid. The CO2 in that era was already high so an event like that would cause disastrous warming to an already hot planet. Compounded with the gas ravaging plant life, ocean acidification and a damaged ozone would lead to an extinction.
For the Deccan traps the global cooling was likely the killer. The rate of magma expulsion alone was enough to cause major cooling, the gas would have covered large regions of the globe and, there was the issue of an impact winter happening at the same time as all of this. The cooling would have covered most of the globe in ice while little to no sunlight reached the Earth. This would be quite different from what the species of the world would be used to. The warming from the CO2 would take thousand of years to overcome the existing climate, A decimated plant life would slowly recover as the climate warmed and things would soon go back to being relatively sustainable.
The Siberian traps is responsible for the largest extinction event by far but what caused it? The warming or cooling? Why not both? Everyone know about how the event happened over carbon rich rocks but the fact that 25% of the material was pyroclastic doesn’t get the attention it deserves. That means 250,000 to 1,000,000 cubic km of tephra or DRE of material were ejected. I don’t which it is but both are possible. At the minimum that is a Campanian Ignimbrite every thousand years and the most that is a Huckleberry Ridge Tuff in the same time frame. The Siberian traps was one of the most intense flood basalts to ever strike the planet and up to 4 million cubic km of magma erupted in a relatively short time-frame.
The effect of disastrous cooling and warming likely worked together to create an extremely deadly environment. The global cooling and gas would have decimated plant life but it would not be enough to cover large portions of the world in ice and as such when the warming kicked in, there would be almost nothing to dampen it. The ocean acidification in response to this would lead to the oceans breathing out harmful gas that would make the Earth vulnerable to radiation from space. At this point Oxygen would be scarce and all forms of life would suffer. A lack of abundant Oxygen is what I believe is the killer for both the Cretaceous–Paleogene extinction and the Permian extinction. In Both of these events plant life was ravaged to the point where they couldn’t have been viable sources of oxygen while the acidic ocean would decimate oxygen producing microbes. It may sound a bit dramatic but during both extinctions more than half of the world’s life forms were killed.
These eruptions hold plenty of mystery and will always capture the imagination of scientists but may never completely understood in its effects and if it were to happen soon then our understanding would mean nothing as we would be dead. As annoying as I find people talking about this events as an imminent threat, I understand it is out of lack of knowledge, after all when I was twelve I was one of those people. But people who do this knowingly embarrass themselves.