There is a weird beauty to the blueprints for the Tsar Bomba design by Babayev-Sacharov-Trutnev. Never before, nor after, have a bomb reached that level of engineering perfection. It is to date both the largest, and the cleanest, nuclear device detonated.
Compared to the inherently flawed Ulam-Teller design and its derivatives used by the US, the Soviet nuclear bombs are marvels of consistency in brisance and behaviour. And however weird it may sound, safer to be in the vicinity of when they go off, due to the comparatively low fallout.
Anyway, this article is about nuclear bombs and their effect on nearby volcanoes, not about the bombs themselves. The reason for this article is fairly obvious, since the Kims of North Korea is as enamoured with their nukes as Dr Strangelove was, and the vicinity to Mount Baekdu.
The reason I am starting off with the 51 megaton Tsar Bomba is that it will be used as a counterpoint to North Koreas latest 130 kiloton (+/-20 kiloton) based on the Soviet RDS-6 design. It is quite likely that the North Korean design is based on the Sacharov design due to the low amount of detectable radiation.
The original question we got was if the nuclear testing at Punggye-ri could trigger an eruption at Baekdu. But, I will try to go a bit further than that in this article and widen the scope to include the geology of the Punggye-ri itself as it sits under Mount Mantap.
But let us start with the age old question of large earthquakes causing volcanoes to erupt since the nuclear device caused a M6.3 earthquake.
Earthquakes and volcanic eruptions
There is to date no instance where an earthquake is proven to have caused a volcanic eruption. The only likely suspect is the earthquake in Quetzaltenango in Guatemala that occurred on the 18th of April 1902 after a 3 month long earthquake swarm. This swarm continued afterwards up until the 24th of October when Gagxanul (Santa Maria) erupted.
For more than 100 years this was seen as an example from the classic foreshock-mainshock-aftershock meme. A more modern approach is to view the entire swarm as volcano-tectonic caused by rapidly intruding magma from depth moving into the volcanic system, that in turn caused a large tectonic earthquake of M7.5 on the moment magnitude scale.
So, in the modern interpretation it is the other way around. The volcanic pre-cursor activity caused the tectonic release.
The same happened at the Amatitlán Caldera as a magmatic intrusion caused a seismic swarm that weakened the faultlines surrounding Guatemala City.
The problem with this idea of large earthquakes causing eruptions is that large earthquakes tend to happen near or in areas where there are an abundance of volcanoes. So, quite often there will be an eruption within a year after a large earthquake. But, from pure statistics we know that at these places it is so common with eruptions that one is almost bound to happen within any random year without any large earthquake occurring. There are after all at least an order of magnitude more eruptions than there are large earthquakes on the planet.
That being said, if there is a large earthquake above M8 occurring within 100km from a volcano that is teetering on the brink of an eruption it could set off the eruption prematurely. But, it is good to remember that we are talking about days or weeks prematurely at best, and that the volcano would have erupted anyway. The only difference is that the eruption is likely to be a tad less powerful since it did not have time to mature fully. The same goes for premature volcanoes as for premature born children, they tend to be smaller than if they had gone the full 9 months.
The state of Baekdu
Against popular belief and modern media hype there is nothing much pointing towards Baekdu being near an eruption. Yes, it did inflate between 2002 and 2003 according to the Global Volcanism Program and again between 2005 and 2008 according to Chinese volcanologists, but volcanoes tend to have many intrusive episodes between eruptions, and there are no current signs of an eruption being close at hand. At least not so close that we can say that it is teetering on the brink of an eruption.
The second thing to remember is that the 946AD eruption utterly destroyed the magma chamber under the mountain. And large magma reservoirs take their own sweet time to build up again. And there are no signs that Mount Baekdu has rebuilt sufficiently for another large eruption, the evidence at hand is in fact quite contrary.
First of all, we know that there is a 5000 year span between the 4105BP (+/-90) Tianwenfeng eruption (VEI-7) and the VEI-7 946AD eruption. This gives us a timeframe for a possible rebuilding phase, and we are as such at the early stages of rebuilding.
We have further evidence for this from the volcanic records of the volcano. Prior to the 946AD eruption the size of the average eruption was VEI-4, but the eruptions after have all been VEI-2 at best.
So, even if Baekdu was teetering on the brink of an eruption, and a large earthquake occurred next to it, there would be a bit of ash sprinkled in the vicinity of the volcano. So, even in a worst-case scenario it is not the doom and gloom that people dream up.
Mount Baekdu and Punggye-ri
Let us start off with the distance between Mount Baekdu and Punggye-ri. The nuclear test site is located 114 kilometers southeast of Mount Baekdu, so we would need a sizeable earthquake to theoretically set off an eruption. And the North Korean man-made M6.3 is not even by a longshot large enough to do anything untoward.
The North Korean bomb used in the latest test was utilizing a fusion doping stage and was not a true hydrogen fusion bomb, presumably it was of the Sacharov RDS-6 design, since the blueprints are readily available and on hand by pretty much every nuclear interested country on the planet. As such it is at least 3 design steps away from the Tsar Bomba.
And here is the reason I am using the Tsar Bomba as an example, it is the only detonated nuclear device able to produce an earthquake larger than M8. To be specific, it would if it was detonated below the surface produce an M8.35 earthquake on the moment magnitude scale.
At best the North Koreans could produce something like it in a decade. But, here is the next point. They will never do it. Why now? Well, first of all, The Tsar Bomba is in itself the largest joke in the history of mankind since it is unusable, and if you are not having the entire Soviet Hinterlands to test it, it is also untestable.
If Kim decided to test it underground he would produce a VEI-6 radioactive caldera about 5 kilometres in diameter. In the process he would make half of his country uninhabitable. An aerial test would be even worse.
The fireball of the Tsar Bomba was 10 km in radius and the foot of the mushroom cloud was 40km wide. Everything 100km out from the detonation would be a total loss and all building 250 kilometres out would be damaged with a high rate of dead people. In other words, his country would be gone from right under his pudgy little basketball-playing feet.
Instead he is far more likely to go for the standard 700 kiloton nuclear device, based on the Soviet RDS-37 design, that is the current favourite to place on an intercontinental missile. Or, try to build nuclear devices that are purpose-built for creating electro-magnetic pulse-fields (EMP-weapons). The rationale for that is that any viable enemy of his is relying heavily on electronics on the battle-field, and his troops are in the electronic stone-age, thus levelling the playfield to his advantage.
But let us say that Kim is nuts enough to blow away his own country just to set off Baekdu, then it would be theoretically possible via using a Tsar Bomba at Punggye-ri.
So, let us strike out the idea of a North Korean nuclear device causing a volcanic eruption, and let instead look at the real geologic threat.
Punggye-ri and the collapsing roof
There are two reasons that the Chinese are ever more miffed at Kim and will sooner or later do something about his nuttery. The first reason is that Kim is trolling the Chinese by either launching a missile, or detonating a nuke, every time that the Chinese President Xi Jinping holds an important speech. I guess that places Trumps relative importance a bit aback.
The second reason is that China has a veritable army of geologists, seismologists and geophysicists that are every bit as good as their western counterparts, and they are very well funded and well equipped.
And it is their discovery that will force the Chinese to take action. What they found was that two M5 earthquakes happened at the same place as the latest nuclear test within 8 minutes after the detonation.
This is caused by the little-known fact that a nuclear underground detonation causes a cavity to form below ground, and since the North Koreans have been using the same site for all of their nuclear tests there are now 5 cavities of ever increasing size.
The Chinese scientists have now concluded that the entire site is geologically unstable and that the mountain is likely to collapse releasing all the pent up radioactive material. But, as of now we do not know the timescale it would take for the collapse to occur. But, it is believed by the Chinese scientists that a sixth nuclear test at this site would cause an imminent collapse.
It may sound like this is a good joke on Kim and the North Koreans, but a collapse of the test site would be affecting both the South Koreans and the Chinese populations directly.
Footnote: This article is skirting the boundaries of the rules of Volcanocafé since we try to stay away from politics. But, I felt that this time there was no way to stay away from it due to the location of the volcano at hand. I would though like to implore people to keep the comments as un-political as possible and to stay civil.