Sections of the Earth have been divided off by impassible barriers. For a very long time in some cases. Eons. Some, of course, go desert, because there's not enough water included, for example. Societies may rise and fall, mountains crumble, etc. Let us assume people cannot go over or under the barriers, and weather continues straightforwardly, even though it obviously wouldn't. It's a mystery. What might be some of the more interesting things that would be discovered the day the walls opened?
[[Note: two clarifications were received from the asker: One is that the barriers are completely impermeable, including to air, and the other is that the areas can be very large (possibly continent sized) or very small, and may last for very short amounts of time, or as long as stated.]]
ASTRONOMY/GEOLOGY: a unit of time equal to a billion years.
GEOLOGY: a major division of geological time, subdivided into eras.“the Precambrian eon”
Honestly, pretty much anything you could think of could happen on two sides of those walls in that amount of time. If there are humans on each side of those walls that continue to live, they most definitely would not still be the same species by the time they were reunited. Nevermind societies and cultures rising and falling, whole new species would arise and go extinct. The world would probably be unrecognizable, and the different parts that have been separated would almost be like different planets because of the diversity of life that would be found from one to the next.
The presence of these barriers would definitely have a heavy impact on how weather would behave, and could change climates if they are . What if one area is primarily tropical rainforest, and eventually the amount of oxygen in the air rises significantly higher than what is currently earth normal? Big bugs would happen (think carboniferous period), among other things. Fires would probably burn more easily (don’t quote me on that, I am not a physicist, but greater fuel availability would make it make sense). Then, think about what would happen when the walls fell and that area suddenly mixes with the rest of the air. If creatures living there had evolved to take advantage of the higher oxygen content, and suddenly were deprived of that, many of them would have difficulty surviving (or just die outright.)
Now, some of the shorter-lived barriers might have much lesser effects. Different cultures might develop if kept apart long enough, or cultures might eventually begin to assimilate and merge if stuck in an area together. In today’s world, a lot of how nations behave is based on resources and global pressure; most governments can’t get away with subjugating their people or invading another country because other countries would step in to stop them, but what if that pressure was removed? Or, what if a country with few natural resources was suddenly cut off from imports/exports, and had to make do with what they had at the time?
The possibility of these things happen might even encourage countries to try to become more independent and autonomous, just in case a barrier happens.
One thing that the Pylons and I agreed on is that you’ll definitely need to develop a set of rules about the barriers and how they behave, and stick to them like glue. Are there any known causes? Do they follow specific rules? Are they a certain shape? Do they have an upper limit? (for instance, if someone from inside a barrier’d area tried to go into space, would they succeed?) How far DOWN do they go? (If you want to keep things simple, have them stay within the earth’s crust or they might disrupt electromagnetic fields). Can sound get through? Light? Waves of any kind? (so, is any verbal/visual/electronic communication possible?). Is there any way to predict when and where a barrier will appear, and/or when an existing one may disappear?
If the barriers have ceilings and are impermeable to light, life within would cease pretty quickly because no sun would get in, unless you make some sort of rule or exception to allow for this.
Let us know if you have anything else to ask, and good luck with your world and your barriers!
