No doubt surreal, but a single sub destroy the world? That piqued my interest so took a quick look and found an article [1].
This article states that "even a single vessel [submarine] could reduce as many as 288 city-sized targets into radioactive ash in less than 30 minutes." Later in the article they say that the Ohio class is capable of carrying up to 24 UGM-133 Trident II D5 submarine launched ballistic missiles. Each ballistic missile can carry as many as 12 W88 475 kiloton thermonuclear warheads. For comparison, the one that struck Hiroshima is estimated to have been 10-20 kiloton. So the Ohio class can delivery up to 472 x 12 or 5,700 kilotons (5.7 megaton) or ~285 x the energy release of Hiroshima.
- EDIT: 472 x 12 X 24 = 137 megatons or 6,796 the energy release of Hiroshima.
By comparison scientists have been speculating the scale of the energy release of the eruption in Tonga [2]: "Jim Garvin, chief scientist at NASA's Goddard Space Flight Center, said the eruption of the Hunga-Tonga-Hunga-Ha'apai volcano on January 15 released "hundreds of times the equivalent mechanical energy of the Hiroshima nuclear explosion". The article goes on to say that preliminary estimates are between 4-18 megatons. That energy release created a cloud ~650km / 400mi in diameter. "The cloud would obscure most of Great Britain and the east coast of Ireland. It is almost the same size as mainland Spain.".
EDIT: So an Ohio class SSBN could unleash ~136 megatons which is 7.5-34 x the energy release of the Tonga eruption.
The eruption occurred undersea whereas nuclear warheads detonate above ground as an "air blast" or close to sea level as a "surface blast". "Tactically, surface detonations can be seen as an effective means to obliterate a specific target and surrounding ground forces." [4]. "Unlike surface blasts, air blasts produce almost no local fallout upon detonation. Instead, air blasts are more effective in producing high levels of over-pressure over larger areas and increased yields of thermal radiation.".
So what's my conclusion from this short research? The sources suggest an Ohio class submarine could destroy 288 cities in 30 minutes. No argument there. But destroy the world? It seems evident Earth itself would remain in it's current spherical shape but it would be terribly perhaps irreversibly poisoned, taking a lot if not all life with it. As Nevil Shute puts it in "On the Beach" (New York: William Morrow and Co., 1957) "there would be no “over there,” there would only be “here.” Whether scarred by blast and fire from a nuclear war, no place would be spared the inescapable lethality of the resulting radiation". "Global thermonuclear war is just that, a war against the globe, against the Earth itself."
Thanks parent for fueling a perfect little distraction from my long list of important tasks today :)
[1]https://nationalinterest.org/blog/buzz/these-5-submarines-co...
[2]https://edition.cnn.com/2022/01/24/asia/tonga-hiroshima-bomb...
[3]https://graphics.reuters.com/TONGA-VOLCANO/lgpdwjyqbvo/
[4]http://large.stanford.edu/courses/2019/ph241/abbate2/