Nothing quite like a line coming out of nowhere to make you go "Well, that'll clearly be important later."

There's a line to walk between leaving an obvious breadcrumb trail so audiences know the whole time that A Thing is going to happen, and are just waiting for the chracters to realize it, and leaving hints for only the most savvy audience members to pick up on the first read through.

Misdirection is your friend.

If you want to include important details that audiences can but aren't supposed to notice, you should hide them as something else.

I have a natural disaster that needs to happen in a WIP, and then cascading plot consequences coming from it, but "natural disasters" aren't a big focus of this story and tossing in a Surprise!Earthquake to keep the plot moving out of nowhere, even if that's how earthquakes work, is not how quality fiction works.

But if I start mentioning it, it's a concept so out of left field that the reader would immediately notice and wonder why I'm randomly talking about earthquakes.

So: Misdirection.

First, I have two characters talking about fishing, a pre-established concept, and how much of their food survives off hydrothermal vents that are only in their region, reminding the audience that the geography is unstable without saying any of that. We're just talking about fishing.

I have a character already unused to weather and natural phenomena that other characters take for granted, necessitating an explanation of basic concepts like lightning and thunderstorms. But it's not exposition, it's a fundamental trait of this character and their growth and flaws, self-concious about not knowing these things.

I have baby quakes happening during a later scene, ones that every other character would dismiss as just a thing that happens sometimes, meanwhile the narrator notices, as they've never experienced one before, necessitating a call to attention to explain it to them, and thus the audience with them, while the narrator complains about being patronzied to. But we're not really talking about earthquakes, are we? No, we're watching this character get insecure about another gap in worldly experiences.

The whole time, I am priming the audience for the possibility of a natural disaster that you probably wouldn't expect, but would see coming after the fact as something that makes sense for this world and this story.

All this is so Surprise!Earthquake has as much setup as an unpredictable geological event can have because, when you toss in an "act of god" to fuck with your characters, it has no agency, it's just the hand of the author deciding to throw a wrench in things entirely outside any characters' power and independent of their choices. So having it as embedded in the story as possible instead of coming out of nowhere helps it feel less random and contrived.

Draco likes it soft and slow.

Ron hates being around either of them when they get it because their moans are frankly indecent.