My Kepler Bb planet has 4 moons and is habitable. So that is good. But all 4 of these moons are major moons which while indeed possible, could be a problem.

You see, these moons are in resonance so regularly you will get moons eclipsing other moons. This makes eclipses much more complicated because you would not only have to divide it into solar and lunar and those into Partial, Total, and Annular for solar and Penumbral, Partial, and Total for lunar but know which moon or moons is/are causing the eclipse.

So for example you could have a 2 moon total solar eclipse.

As long as the moons rarely line up, this is fine. But if all the moons line up, something catastrophic might happen. I am talking about of course, a volcanic winter.

Now of course anyone living within miles of the volcano is in immediate danger. With a supervolcano, miles away from the volcanic eruption could be lava rain, literally lava falling from the sky like rain causing volcanic fires and deadly burns both from the lava and from the fire. But what about hundreds or thousands of miles from the volcano? This is also a danger zone but for a totally different reason. Instead of deadly heat from lava and fire, there is extreme cold from all the tephra spreading across the planet. For people not adapted to the arctic or Antarctic, this could be a serious problem. And even arctic aquatic animals might die from lack of oxygen due to all the ice and thus their predators might die off as well.

So you could express a volcanic winter as being like a global cold wave and during the eruption a heat wave relatively close to the volcano. Volcanic winters here on earth can last for up to a year. This volcanic winter from a supervolcano explains why it was so cold in The Year Without a Summer, even as far south as ohio, it was as cold as the arctic is now, deep negatives.

So then why not have all the people move down deep into the underground city where geothermal energy will keep them warm?

Well I could, except I can't. Why? Well for 1 thing, who is going to cook and harvest and do everything else? They are going to have to regularly go into the arctic weather. This means that frostbite and even freezing to death would be a common occurrence. And what about pregnant women? They won't do well in arctic weather and so the fetus wouldn't either.

So this means 1 of 2 things:

1) Have women go out into the cold regularly and try to induce a miscarriage or if far enough, labor


2) Have all the women huddle up in groups deep underground and only have the men regularly go out into the cold to work on expanding the civilization or to cook or to harvest or whatever they need to do

Truly, neither one is a good option but I would say option 2 is better.

Anyway, I am wondering, could this eclipsing of moons when it gets to the extreme(total lineup due to resonance) lead to an eruption of a supervolcano or even multiple supervolcanoes and thus lead to a long and harsh volcanic winter throughout the planet due to tidal forces or is that too extreme for multiple moons of an earth-like planet?

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    $\begingroup$ Check your assumption: why would a lineup trigger extreme volcanism? Gravity is quite weak - if the moons are so close/massive that the tidal forces are strong enough to trigger volcanic activity, then the moon system won't be stable - they'd coalesce in a single one over time. In the ages preceding the "collision", one can probably see "tidal heating" - happens to Io under the influence of Jupiter - hardly something to be considered a habitable environ. $\endgroup$ – Adrian Colomitchi Jan 18 '17 at 3:22
  • $\begingroup$ But our moon causes significant tides on the earth's surface. And that is just 1 moon. Multiple moons would mean more tidal forces and if lined up just right(those eclipses I am talking about), those tidal forces while between 2 moons wouldn't be all that much, between the whole system of moons and the planet would be significantly higher than any other time in the complex lunar cycle. I mean you could view a lined up system of moons as 1 large moon of the same mass as the total mass of the moons, again lots of tidal force between the moon system and the planet $\endgroup$ – Caters Jan 18 '17 at 3:27
  • $\begingroup$ So I don't see why 4 moons lined up perfectly and in resonance couldn't cause volcanism in 1 small area of the planet that leads to a global volcanic winter while having the moon system still be stable. It should be possible that with significant tidal force between the moon system and the planet but not between individual moons that volcanism on the planet occurs but because of the resonance the moon system stays stable. $\endgroup$ – Caters Jan 18 '17 at 3:34
  • $\begingroup$ "But our moon causes significant tides on the earth's surface." Tides of water - the magma is significantly denser and highly more viscous than water. And no, "significant tides" happens only around coastal areas in which the entire tide bulge of a "whole ocean" needs to dissipate on gradually shallow depths - inner seas experience very small tides (e.g Mediterranean basing, Baltic Sea) and the height of the tidal bulge in mid-ocean is around 1m. $\endgroup$ – Adrian Colomitchi Jan 18 '17 at 3:43
  • $\begingroup$ "So I don't see why 4 moons lined up perfectly and in resonance" - because this is not a stable system - either the lineup causes small perturbations and the system will decay slowly over ages or, if strong enough to cause volcanism, will be unstable and rather felt worldwide than in a single area. Volcanism in a restricted area caused by a lineup may happen as an isolated event if the conditions are right (the lineup is the straw that breaks the mountain back), but this have little to do with the lineup and more to do with the accumulation of condition prior to the event. $\endgroup$ – Adrian Colomitchi Jan 18 '17 at 3:52

That won't work, for lots of reasons.

While it's true that such a high-gravity scenario would trigger some volcanism, as evidenced by Io, a moon of Jupiter, it takes a significant amount of gravity to do so! Calculating tidal bulge and heating is not my specialty, but you will need something closer to the mass of Jupiter, rather than a couple small moons.

Unfortunately, those moons have to be small - you can't just make them bigger to fix the scenario. More than two bodies of about the same mass don't like to settle into healthy orbits around each other without colliding or flinging one out, and it's very difficult to form multiple large moons around a terrestrial planet. Theoretically, your system could exist, but in practice, there are too many factors that would eventually get rid of the extra moons - and fast.

Even if a stable system somehow formed and existed, the moons would be too small to hold an atmosphere, meaning volcanic debris blocking out the sun would be the least of your problems - and even if there were an atmosphere, an extremely volcanic world would have deadly earthquakes and a poisonous atmosphere.

Consider just putting the moons around a gas giant, and wearing pressure suits and breathing apparatus to survive.

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I don't think the actual magma being pulled from the ground would be the catalyst of your volcanic winter. In volcanoes on earth, the effect of lava is minuscule compared to the effect of the massive cloud of ash. While the tidal effect of the moons may not be enough to cause an increase in Hawaiian(lava) eruptions, it could easily increase Strombolian(gas bubble) eruptions.

Gas Explosions tend to do more environmental damage because clouds of poisonous gas and hot ash can kill animals and block sunlight at a greater distance than lava and flying rocks can reach. As clouds of ash block the sun, temperatures drop, plant life dies, oxygen levels drop, animals start to die. These effects could easily cause a "volcanic-winter."

The best defense from this type of calamity would be self-enclosed structures, either domes or underground, with artificial light, farms, and livestock.

As far as who should do the dangerous work, remember a woman must commit nine months to a single pregnancy, while a man may commit as little as five minutes. Because of this, sterile individuals are most expendable, men are slightly less expendable, and women are precious. As far as the continuation of the species is concerned.

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