In this scenario, which natural disaster is more likely?

Question

I am writing a story called Life on Kepler Bb. It is about this earth like planet with 4 moons orbiting a double binary star and the humanoids that live on it. The planet has tectonic plates so earthquakes do happen

I have gotten through lots of events. Here is just a fraction of those:

First shelter built

First child

First trip to the arctic

First pirate

And this is over 10 chapters that could easily be expanded.

Anyway I was thinking of having the 11th chapter be about a severe natural disaster that the humanoids haven't survived before. I am not sure what natural disaster though. I do know that this is far inland so it wouldn't be a hurricane or any other oceanic natural disaster.

The humanoids in my story have survived severe thunderstorms and the first pirate has survived very rough waters including the roaring forties.

Maybe a description of their civilization would help.

Civilization description:

Each male humanoid builds a shelter for him and his eventual wife. Once the male marries a female they start expanding their home both on the surface and underground to have sleeping chambers, children's rooms, etc. These homes are also connected to each other via underground tunnels. They use static electricity with positive charge to keep the civilization from crumbling and to waterproof their shelter so they don't get soaking wet inside when it rains. This also protects them from lightning strikes.

They don't have anything as far as tornado protection is concerned but they have survived tornadoes. They have also survived the worst of blizzards.

These humanoids don't have the power to survive in extreme heat(Hotter than desert temperatures), at least not yet.

Given all of this about my world and my humanoid civilization what natural disaster is more likely to form, a volcano or an earthquake?

And given that these humanoids have a mainly underground civilization what should they do if they get an earthquake or if a volcano forms? There might not be enough time to evacuate everyone unless there are lots of humanoids with the power of flight. Even then there might not be enough time if it is a volcano forming. I know that the lava would burn through any building or home.

Answer 1

If you're interested in potentially predictable but still somewhat implausible scenarios:

A certain spot on the equator has a supervolcano. No-one is quite sure why, but 'scientists' believe that it's due to regular tidal stressing caused by all the moons passing over that spot more regularly than any other spot on the surface. What they don't know is that every few thousand years (due to some major quirks of astrophysics) the four moons and the sun line up over that spot, leading to major tectonic activity followed by a really cool solar eclipse, then the eruption of the supervolcano and the resulting dust clouds blocking out the sun for twenty years and killing almost all life on the planet. There are some archaic references to dragons eating the sun when the moons align, but who believes in astrology, right?

Cue story hook with scientists realising this will happen, warning people with just enough time to save the world by building a giant boat.. Wait. No. That's 2012...

Answer 2

Volcanoes and earthquakes both depend on tectonic plates and activity, so it really kind of depends. Earthquakes happen when tectonic plates shift and bump. Volcanoes happen when plates get a gap, allowing magma to seep up.
Which is most likely kind of depends a lot on the geography, however, there are very few new volcanoes created, while earthquakes happen every day, so unless they built their town near an existing inactive volcano, I'd go with earthquake.

The effect would depend on how strong the earthquake was, and how stable the cavern system they are in is. It would range from dust falling down, to the cavern collapsing. There would most likely be signs leading up to the quake, so if they have anyone with geology knowledge then there could be some warning.

As another thought, a solar flare has a lot of potential as a natural disaster on a planet with binary suns.

The people are living underground, so the flare wouldn't have much effect at first, but disrupting communications and electricity, altering weather, killing crops, increased radiation (depending on if the planet has a magnetic field), are a few things that could happen.

Answer 3

Given that you have a binary star and four moons influencing your planet, tectonic activity may be a factor in geology there, depending on the geological age of the planet. A young planet would be more unstable than an older planet which has had enough time to allow seismic activity to settle down.

Another interesting article here.

And having your inhabitants living underground would probably leave them pretty susceptible to any seismic events.

So an earthquake would be particularly effective at making life difficult for them.

I would guess that they use the materials at hand on the planet, and being 'earth-like', you might have trees or similar, so the tunnels and habitations would likely be shored up with wood.

Iron would likely be available (geological instability would probably expose all kinds of minerals), and steel able to be produced. Do you have any industrial capacity?

With a large percentage of your population underground at any particular time, an extensive tunnel collapse would hit pretty hard. Some of your underground areas may stay intact, but be cut off from the surface as shafts and access tunnels become inaccessible, needing rescue operations to get people out.

Answer 4

You are on a different planet, so have some fun; change the rules a little.

Day 1 : a 1.0 quake rocks the settlement. broken dishes and dust from ceilings.

Day 2 : a 2.0 quake hits at the exact same second. No tunnels collapse, so settlement is fine but people are worried.

Day 3 : a 4.0 quake hits collapses all underground caves, but everyone is okay because they were expecting it.

Day 4 : ...

How far it goes depends on how much adventure your charactes can stand.