We’re finally back with another worldbuilding post! Sorry this one’s a bit later than I’d hoped for. Long story short, I wrote the script for this, accidentally deleted it when my laptop was on the fritz, then ended up wiping out on my motorcycle. I’m fine. The motorbike’s not, but I’ve got no permanent damage. But the recovery process has made rewriting the script and doing the more technical art for this episode take longer than I would have liked. So, my apologies for it taking so long, but it’s finally here! We’re finally going to start talking about one of the things most people think about when they discuss worldbuilding: designing the physical geography of your world. Today’s post is going to focus on land forms: your mountains, valleys, and so on. As always, I’m going to rush through a few disclaimers, and then we’ll get right into it.
First, this post is an overview to help you get started, but I am not an expert in geography. If your story depends on having deeper, scientifically plausible worldbuilding than I end up covering here, please make sure to do further research.
Second, I’ll be speaking about how geography for an Earth-like world works. Speculative fiction writers out there should feel free to not make an Earth-like world.
With the first and second disclaimers in mind, remember that your story is your story. Particularly if you’re designing a fantasy world that includes a magic system that could have impacted the development of your world, don’t feel like you have to be 100% beholden to scientific law. You may still want to know what the rules are so you know how and why you want to break them, but feel free to break any rules that aren’t helping your story be the best version of itself it can be.
With that out of the way, before we start talking about mountains and valleys and plains (oh my!), we need to talk about something else, because it’s going to affect where those features are likely to end up. So, let’s talk about Earth’s tectonic plates.
TECTONIC PLATES
Beneath the Earth’s oceans and crust, the Earth’s surface, the lithosphere, is broken up into tectonic plates. These plates come in many sizes and shapes, and they float upon the Earth’s asthenosphere, slowly moving over the course of millions of years.
There are two different kinds of tectonic plates. Continental plates are thicker, whereas oceanic plates are thinner and denser. As these plates bump around, they can cause earthquakes, tsunami, volcanic activity, destroy some of the Earth’s crust, or create new crust and geography. What kind of natural disasters or new geography happens, though, depends on what kind of plates are interacting with each other and how.
First, let’s discuss convergent boundaries and the three types they come in. Convergent boundaries happen when two plates collide.
When a continental plate and an oceanic plate collide, the denser of the two—the oceanic plate—slides beneath the continental plate in a process called subduction. When this happens, part of the crust is destroyed. A trench is formed where the continental plate meets the oceanic plate, but the collision also can cause magma to rise through the continental plate. That volcanic activity can then form mountains. A converging continental and oceanic plate may cause earthquakes, tsunami, and volcanic activity.
An oceanic-oceanic convergent boundary happens when two oceanic plates collide. When this happens, the denser of the two oceanic plates, usually the older of the two, subducts below the other. It’s much like what happens with a continental-oceanic boundary but happens under water. There will be a trench where the two plates connect and magma can rise through the upper of the two plates creating undersea mountain ranges or volcanic islands when those mountains rise above sea level.
When two continental plates collide with each other, things happen a little differently. Neither plate will subduct below the other. Instead, the plates will buckle as they come together, forming mountains along the fault line. Mountains formed in this way are called “fold mountains.” There will likely be earthquakes.
The second kind of boundary is called a divergent boundary, and these happen when two plates pull apart. When two continental plates pull apart from each other, the form a rift valley, and the gap they create is filled with new crust. Active rifts continue to widen over time. Often these valleys fill with water and form a rift lake, but they don’t have to. As the two plates pull apart, they may allow magma to rise through the rift and form volcanoes.
Again, basically the same thing happens in oceanic-oceanic divergent boundaries, but under water. Rising magma will thin the edges of the plates and push them upward, forming an undersea ridge and new ocean basins. Where these ridges rise above sea level, they form volcanic islands.
Lastly, the third type of boundary is called a transform boundary. These boundaries happen when two plates grind horizontally alongside each other in opposite directions. In continental-continental transform boundaries, such as at the San Andreas Fault, the grinding of these two plates can cause very severe earthquakes.
Oceanic-oceanic transform boundaries are unusual in that they happen to be interspersed with divergent boundaries. This means they will form a zigzag pattern where all the zigs are divergent boundaries and all the zags transform boundaries. Once again, you can expect earthquakes.
Those are the three types of boundaries, but because plates have varying shapes and sizes, and because they will interact with more than one other plate at a time, a single plate will have multiple kinds of boundaries as it collides here, pulls apart there, and slides along over there. This will allow you to have some interesting diversity in your geography.
So that’s the basics of plate tectonics. Is it necessary to design the plates and fault lines in your made-up world? No, many of you won’t find it worth your time, and that’s okay. Simply having a basic knowledge of how plate tectonics work should be enough to help you design your world. However, if you think designing the plates for your world will help you better envision it or will help you come up with a more interesting or believable world, here are a few quick tips to help you design your plates.
First, make sure your plates come in a variety of sizes. If you aren’t interested in designing your whole planet and are focused on a single country or continent, it’s simple enough to just design a few plates more or less however you want. However, if you’re worldbuilding for an entire planet and that planet is globe-shaped, make sure the top or your map lines up with the bottom. Same with the left and right sides.
Once you’ve got the shape and placement of your plates figured out, decide which are oceanic plates and which are continental. If you’re going for an Earth-like world that is two-thirds water, you will of course want to make sure your oceanic plates are covering that much of your map.
Next decide which direction each plate is moving in. This will let you know where the converging, diverging, and transforming boundaries are. You might want to colour code these boundaries for easy reference.
Now you’re ready to decide where to put the continents of your world.
CONTINENTS
There is no hard and fast rule for what shape your continents should be in relation to your tectonic plates. You can see from this map that Earth’s continents very roughly tend to follow the shape of the plates they’re on, but there is quite a bit of room to get creative. A single continent can span more than one continental plate. On the flip side, there may also be places where a thinner continental plate dips below the ocean and only a small part of the plate appears above sea level. You may find it easiest to keep your continents relatively in line with the shape of the plates, but definitely don’t feel like you can’t get inventive.
Now that you’ve got an idea of where your continents are and the fault lines, you can start deciding where to put your landforms. So, let’s start with your mountains.
MOUNTAINS
We’ll get into this more when I make a post on climate, but mountains have an impact on the climate and biomes around them, and that means they’ll have an impact on where pretty much all your other geography is likely to go. In short, one side of your mountain range is likely to be lusher and greener than the other side, and the taller your mountains are, the more drastic the difference between the “wet” and “dry” side is likely to be. So, once you’ve decided what your continents look like, you’re probably going to want to place your mountains first, because that will make it easier to decide where your rivers, valleys, deserts, and so on need to go.
In discussing tectonic plates, I already mentioned how mountains form along fault lines and can come in two types: volcanic mountains formed when magma surfaces, and fold mountains formed by the converging of two continental plates. However, there are also two other types of mountains: block mountains and dome mountains.
Block mountains are formed through the breaking of large areas of Earth’s crust where those broken segments are then vertically displaced. One side of the mountain may have a steep incline while the other side is a gradual climb, or they may have a steep incline on both sides.
Dome mountains are formed when large pockets of magma move toward the Earth’s surface but do not break through it. Instead, they bubble up, pushing up against the rock and making it swell into a dome shape. The magma then cools and hardens before having a chance to break through the surface.
Many of your mountains are likely to appear in mountain ranges, but solitary mountains can and do form too, so if you want to have your own Lonely Mountain in your world, that’s not beyond plausibility, because fault lines are not the only place mountains might appear.
Another reason you might have mountains is because of hot spots in the Earth’s asthenosphere. The plates for your world will likely have places that are thinner and more vulnerable than other segments of the plate. When a plate moves across a hot spot in the asthenosphere, those thinner parts of your plate may give in and allow magma to surface, creating a mountain. As your plate moves across that hot spot over time, you may get a chain of mountains following the direction of the plate’s movement. This is how the Hawaiian islands were created.
HILLS
Now that you’ve got the basics of mountains down, the next feature you might want to design are your hills. Hills can be manmade, but when it comes to natural hills, the easiest defining difference between mountains and hills is simple: height. Different places around the world will have different guides for how tall a hill has to be before it becomes a mountain, but this is effectively the main difference between them. What this means is that many hills form the same way mountains do and can be expected to be found in the same places. Often a hill will simply be a young mountain that hasn’t reached its full height yet, or they might be old mountains that have been eroded down over time. It’s common to have a range of foothills following parallel to a mountain range.
But there are other ways hills can form too. Hills can be created through glacial activity. As glaciers expand and retract, they shape the land beneath them and can create hills. So, don’t just look for fault lines when you want to place your hills. Look at polar regions and areas of high altitude where glaciers might have existed during your world’s ice age. Those areas will be a great place to include hills.
Another way hills can form is through irregular erosion, such as by wind. This is how you get your shifting sand dunes or snow drifts.
Hills on earth can also be formed by plants or through animal activity, such as anthills. Maybe your world has burrowing creatures that make enormous mounds. Do they build them haphazardly? Or maybe your characters realize there’s a dangerous monster in the area when they find hills that arrange in a certain, distinct pattern.
OTHER ROCK FORMATIONS
Besides mountains and hills, there are many other kinds of rock formations, particularly in places where you have more easily-eroded rock meeting up with water or wind. Your coastlines may have vertical cliffs where the sea has broken off chunks of land. You may have sinkholes or caves where the type of rock is soft enough for water to erode holes or elaborate tunnels underground. You might have rock that has been worn into chimneys or windows through a mountainside. It would take way too much time to get into all the different fascinating formations you can find on Earth, but if you want to make your geography exciting, remember that your mountains and hills can take all kinds of interesting shapes in and of themselves, but there are also many other kinds of rock forms you might have fun playing with too.
VALLEYS
Valleys are deep, elongated depressions in the ground formed by erosion. Usually they follow a river or stream, but you can have dry valleys too.
I’m saving my discussion on water features for the next worldbuilding post, but when deciding where your valleys should be, you’ll definitely want to pay attention to the likely places your streams will end up. Your streams, creeks, and rivers are going to play a heavy role in where your valleys go, because erosion caused by water is one of the main ways valleys form. Streams beginning in the mountains or other areas of high altitude will cut through rock and earth to create valleys. However, glaciers can also form valleys, so make sure to pay attention not just to where your streams are, but also to where your glaciers are. Or were.
One of the easiest ways to differentiate between kinds of valleys is through their shape. Imagine cutting a valley perpendicular to the path it follows, then imagine looking at a cross section of it. There are three main shapes that cross section might take.
V-shaped valleys are, as the name suggests, shaped like a “V.” They’ll have slanted sides cutting down to a narrow floor. These valleys are made by young streams and rivers, meaning you are likely to find these valleys nearer the source of the stream, such as in the mountains, where the water is more likely to be narrower but faster.
U-shaped valleys are, as you probably guessed, shaped like a “U” instead of a “V.” These are valleys that have been widened by glaciers. They’re likely to have pretty steep sides and a rounder bottom. Again, they may still have a stream or river flowing through them.
The third type of valley is a flat-floored valley. Again, as the name suggests, flat-floored valleys have much wider and flatter bottoms. These valleys are usually found where streams and rivers are wider, slower, meandering, and older, meaning they’re farther away from the water’s source. Widening or flooding of these rivers over time can flatten the valley around them. The Nile river is a good example of a river through a flat-floored valley.
A valley might start off as one shape and turn into another over time. A valley formed by a mountain stream, for example, might start off as v-shaped but over the course of time end up u-shaped due to glaciers expanding down the mountain and widening the already-existing valleys. Similarly, a single valley might start off as v-shaped but transition to flat-floored as the river forming the valley ages, getting farther from its source and widening.
As already mentioned, streams and rivers are common to find at the bottom of a valley, but these streams may dry up, leaving the valley itself dry. Maybe a valley once carried a river but changing geography upstream rerouted that river and the valley no longer hosts a stream. Or, maybe in hotter, drier parts of your world, you have seasonal rivers that flow during cooler, wetter seasons but evaporate during the hot summer. Or you may have a stream that disappears underground, leaving the valley above.
PLAINS
Plains are one of the most common features of Earth’s landscapes, covering over one third of all land area. They are an expanse of land with little change in elevation. You may have a hill here or a small thicket of trees there, but plains will largely be flat, treeless land.
Plains may form in a few ways. Depositional plains are formed because something—maybe a river, glacier, or volcanic eruption—left an expanse of sedimentary deposits. Flooding rivers like the Nile, for example, may leave behind nutrient-rich soil, or lava flows may solidify into a plain.
Erosional plains are formed by, as you probably guessed, erosion. Water, glaciers, and wind can eventually erode other geographical features into plains by smoothing them out over time.
The third main type of plains are structural plains are plains which were neither formed by sedimentary deposition nor erosion.
As common as they are, you can expect to find plains in several places. A plain may form at the bottom of a wide, flat-floored valley. You can find coastal plains that may stretch from the ocean and slowly incline toward other geographical features such as hills or mountains. You can also find plains at higher elevations, such as with a plateau.
Another thing to consider, especially once you start designing races or cultures for your world, is that many kinds of plains, as long as they aren’t also desert wastelands or frozen landscapes, are likely to be important places of agriculture. They may have fertile soil, especially depositional plains that continue to get new sediment regularly, but plains also will require less innovation and construction to make growing crops possible, and many plains also have an abundance of grasses which will help in feeding livestock, depending on what kind of livestock the people in your world have the closest agricultural relationships with.
PROJECT: NOVELJUTSU
Years ago, when I had my first ideas for the story of Project: Noveljutsu I had a lot of fun designing a map for my world.
But I also had no idea what I was doing and made a ton of mistakes. So, I took my old map, and I revisited it, making it more accurate to what I’ve learned over the years about how geography works. Starting with designing my plates, figuring out what direction they were moving in, and making a rough guide for where my convergent, divergent, and transform boundaries were.
Now, I kind of got to cheat a bit, in that my story doesn’t require me to design a whole world, just one corner of it, so it was easier for me to design plates that would allow for me to have the features I wanted rather than having to make my features fit the plates. That said, my new map does look different from my old one.
My story has a lot of travel in it, and I knew I wanted to have diverse geography with mountains, hills, plains, lakes, ocean, and maybe even volcanoes. And, now that I’ve fixed up my old map to make sense, this is the end result. We’ve got some mountains that formed by the collision of plates, some volcanic islands to the south, and coastal plains. You might notice that a big chunk still looks pretty empty. That’s because I’m holding off on putting in my valleys and some other features for a future blog post about worldbuilding your water features. For now, I think this is a good start that will give me a lot of room to have some fun with my characters’ journey. What do you think?
CHALLENGE
Your challenge for this post is to make a map of geographical features. You can decide to make a map for a whole world, if you like, but if not, then I suggest at least making a map for a single continent. You can do this for a story you’re working on, or you can simply do it for practice, but for the sake of that practice, even if you never adopt this as your usual worldbuilding process, this time start right from figuring out where your tectonic plates are.
If you’re a speculative writer and you want to, you can try making two maps. Make the first one follow the same rules as Earth’s geography, and then, if you have a magic system or strange, burrowing sci-fi creatures in mind, you can try making a second map where your geography will be affected by those speculative elements.
And that’s it! Have fun!
That brings us to the end of this post. I hope you learned something. What’s your favourite geographical feature to set a story at? Most of my stories end up taking place on plains, but one of my favourite settings to write was a book set in a vast cavern system. I had a lot of fun figuring out how a civilization could survive underground.
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