I'd like to apologize for getting this out so late. I had planned to update the guide every 2-4 weeks, depending on how hard each section was to write and how much life got in the way. Unfortunately for this bit, I had some technical difficulties added to the mix. I still want to update on the original schedule and will hopefully be able to do so consistently.
Enough of me talking. Let's get on with worldbuilding!
Shaping and Scale
By now, you should have found your seed idea and recorded it in detail. If not, see the previous installment of the guide or, if you want to build a world from scratch and see where it goes, continue from here.
Check your seed idea for information on geology or geography. There might not be any, and that’s fine. If, however, your seed idea includes specifics about place, you’ll need those. Figure out if your seed idea requires an unusual place. If so, you will need to tweak your initial worldbuilding to make such a place.
In my seed idea I have flat land with lots of running water and flourishing plant life. It seems to be a wetland of some sort, and not one with really unusual characteristics. Since this is the case (wetlands of all types are quite common), I won’t need to do much in order to create this place. I will, however, need to make sure I have a large, flat wetland near a mountain range, probably in a temperate to subtropical zone.
Now we need landmasses of some sort. Decide what scale you want to work with. Do you want to map the entire planet? Just a continent? An island chain? You will need to map out a fairly large area for the procedure in the guide to work; if you’re unsure about the scale you want, go bigger. I find that a single continent is a good size to start at. If you only want to work with part of a continent, it’s still a good idea to sketch out the whole thing. It’s easier to zoom in than to zoom out.
Draw your landmasses. Any medium will do as long as you can alter it easily. I recommend drawing over a grid, as it will help to determine the scale of geographic features. If you’re having trouble drawing a shape that looks like a convincing landmass and not a blob, go looking for stains, smears, or chips – any random shape lacking straight edges. I’ve found that chipped (not peeled) paint and stains on concrete make great continents. You can also flip shapes around to see if you like them better in a different orientation.
Next, determine the size of your landmasses. I think it’s easiest to do this by comparison to geography you’re familiar with. You don’t need to be technical; “a bit smaller than South America” is a very useful general size. Look up the land area of whatever you’re using for comparison, scale it up or down as desired, and you have an approximate size in square miles or kilometers. Remember that when you’re working in continent-size areas, a little tweaking goes a long way.
I’ve decided to map out one continent.
I want it to be smaller than Asia, but not by too much. The continent of Asia covers 17.21 million square miles, or 44.58 million square kilometers. Since I want my continent to be a little smaller, I’ll round it down to 17 million mi2
(44 million km2
). Doesn’t seem much smaller, but I just took off 210,000 square miles (580,000 km2
) . That’s a little more than the area of Belarus.
When you have landmass sizes estimated, it’s time to scale the map. This is where mapping over a grid starts to come in handy. Count the number of squares that your landmasses cover. The edges will be a little tricky; don’t worry too much about it. Just estimate to the best of your ability.
Divide the area that you’ve estimated for each landmass by the number of squares that are covered by that landmass. The result will be the area of each square on the map. Take the square root of the area to find the length of one side of a square. Write this number down, as it will be important later on. It probably won’t be a nice integer – just round it to two or three decimal places.
My continent covers 582 squares. So:
Landmass area = Area of one square
= 29,209.62 mi2
The square root of 29,201.62 mi2
= 170.91 mi per square side
Write that number down; it will be important later in the guide.
Plate Tectonics and Geographical Features
After your continents are a nice shape and size, you’ll need some features. Start with drawing in tectonic plates. The shapes of your continents will help to guide these. You’ll also want to determine the direction each plate is moving in relation to its neighbors. It doesn’t need to be terribly accurate as long as you have an idea where your edges are and what movement happens along them. There are two different types of plate, oceanic and continental. You will need to know the type of each plate in your map. Basically, oceanic plates are at the bottom of oceans, and continental plates have continents. Not that hard. Note
: Tectonic plates are not an absolute necessity. You can decide whether or not to have them, even if you have a world rather like Earth. However, Earth derives lots of geographic features from tectonic activity, so this guide will provide information for creating a tectonically active world.Faults
are discontinuities in planes of rock; the largest ones occur where tectonic plates meet. We are mostly concerned with these plate boundaries. They can be categorized as transform
, and convergent
occur where two plates move past each other sideways. Plates are not created or destroyed along these faults, but strong earthquakes may occur.Divergent boundaries
are boundaries between plates that are moving away from each other. A divergent boundary between two oceanic plates will result in a mid-oceanic ridge where new seafloor is being created. Between continental plates, a boundary of this type initially creates a rift
, which eventually becomes a rift valley
. Volcanism and earthquakes are possible along divergent boundaries.
Rifting may also produce mountains. Lifted block mountains
occur when chunks of rock are raised above the surrounding area and the land between them slips downward. These mountains have two steep sides separated by valleys; this type of terrain can be seen in Germany’s Black Forest.Tilted block mountains
form when only one side of the block is lifted. They have one very steep side, and the opposite side has a gentle slope. The Teton Range in the western United States consists of tilted block mountains.Convergent boundaries
form when two plates move toward each other. One plate may slide under the other (subduction
), or continental collision
may occur. Subduction
will occur when one plate is more dense than the other, in which case the denser plate will slide under the lighter one. Oceanic plates are more dense than continental ones, so subduction is likely when the different types of plate collide. In this case, a mountain range will likely form on the continental side and an oceanic trench will form on the ocean side – the Andes is a mountain range of this type, paired with a trench off the coast.
If two oceanic plates collide, an island arc
is often formed on the less dense plate, and an oceanic trench on the opposite side of the boundary is likely. Mountains and island arcs formed along subduction zones are most likely volcanic. Earthquake activity is also likely.Continental collision
happens when two continental plates collide. Neither subducts under the other; instead, both plates buckle, creating large mountain ranges. Think of the Himalayas.
You'll want to figure out your plate boundaries and their interactions first, then work in the features that they will produce.
I decided I wanted this continent to be fairly geologically stable, so I put most of it on a huge tectonic plate. It will interact with other plates at the edges, but I’ve kept most of those away from my continent and so off the map. To keep things from being geologically boring, however, I put in a nice continental collision in the east and a subduction zone off the northwestern coast.
And here is the map with the features produced by plate interactions added. I also put in some folded mountains to the south of the continental collision; they are produced by the larger plated folding farther from the collision itself.Another note
: Plate boundaries are not the only faults that will exist in an Earth-like world. Most plates have lots of minor faults within them, and these are often instrumental to building the landscape. Feel free to add these in where you want them. Interactions around small faults will be pretty much the same as those addressed above.
That's all for this section.
is an open-source program that allows you to play with plate tectonics on a sphere. The default map is Earth, but you can use your own maps. Download it here
If you’re interested in GPlates, check out this tutorial
for looking at plate movement using the program. It seems extremely useful.Tectonics
is a plate tectonic simulator that runs in your browser – no download required. It tends to give some odd-looking continents, but it’s a good tool for learning how plates interact. This guide
uses both Tectonics and GPlates to produce fairly realistic results. Worth looking at.