Geologic Worldbuilding Part 1: The Basics

Geologic Worldbuilding Part 1: The Basics

I had actually planned to write a little about how world-building works for a geologist. Then, I started and noticed pretty fast, how terribly complex the whole topic would be and how I was glossing over facts, just so it wouldn’t get too big to read. That also meant I barely said a peep about world-building. Thus, I decided to make it into a little series and build a world with you. Here are the currently planned topics

  • Part 1 – The Basics
  • Part 2 – Mountain ranges (planned)
  • Part 3 – Rivers and lakes (planned)
  • Part 4 – Climate zones (planned)
  • Part 5 – Volcanoes, earthquakes and other catastrophes (planned)
  • Part 6 – Rocks rock! (planned)
  • Part 7 – Summary: Pointers and tricks to make your world geologically sound (plannedI)

Just, so I won’t bore you with some scientific lecture, I have invited Mobs, my little science communicator.

Mobs, als Wissenschaftskommunikator, (c) Janna Ruth

Geological time

Geologists and their sense of time – apparently a breaking point in relationships. When a geologist says, an earthquake is imminent that may be in 10, 50 or 100 years. Or maybe it happens tomorrow morning. They also talk about the recent ice age as if it were a thing that happened a few weeks ago, when it was over 10,000 years ago.

Mountains don’t appear in a human’s lifetime, not even in our species lifetime, though at least that would be a visible change. Equally, it takes a long while for mountains to disappear. The Scandinavian mountains for example predate Pangea and they are still considerable today though that plate boundary hasn’t been active in ages. So, if you are planning to make mountains appear over night or older characters lament how the mountains used to be higher in their youth, then you should consider adding magic or alternative physics into the mix.

Mobs beim Gebirge aufschieben, (c) Janna Ruth

Lifting mountains isn’t exactly a sprinting discipline.

There are, however, geological processes that go quickly. An earthquake can lift or lower the land within the time of its rupture, though that’s only a few metres at most and then not for a while. Volcanoes let whole islands appear from under water during an eruption or they collapse into each other and form crater lakes. Any coast processes are extra quick. Within a person’s life new beach easily forms. At the same time other coasts degrade and break away. With the accelerated sea level rise, this becomes an even faster process.


Plate tectonics

Let’s start with my favourite topic: plate tectonics. As you surely know, the Earth’s crust is broken into many small and large plates. These plates swim upon the so-called asthenosphere, the upper part of the Earth’s liquid mantle. This process leads to plates colliding, tearing apart or passing each other by. The mantle’s convection cycles are the main player in deciding which way the plates go, but that would be looking a little to deep for a place to start.

plate movement, Bucknell University

Bewegung der Platten (c) Bucknell University (

The reason I’m starting with plate tectonics is that the most impressive feature of any landscape, the mountain ranges, only form where two plates meet. Oceans, meanwhile, develop when a plate tears apart upon two conflicting swimming directions. One of the youngest rifts is the East African Rift which also coincides with the Red Sea.

Mobs Plattenbewegung (c) Janna Ruth

Plates can crash into each other or tear apart and drift away

The second most-important thing is that plate boundaries are THE centres of volcanic activity and earthquakes. Ignoring hotspots like Hawaii, volcanos are only found along a plate boundary. The famous Pacific Ring of Fire, that spans from Japan through Indonesia and New Zealand to the Americas, contains 70% of the world’s volcanoes and hosts 90% of all earthquakes. The latter isn’t so surprising if you think of it. Things colliding always leads to shock waves.

About every half billion years a supercontinent forms. Almost everyone knows Pangea where the dinosaurs roamed. Before Pangea there was Rhodinia and scientists have already projected a future super continent. The Pacific will close eventually and acquaint the Americas and Asia. Going from Los Angeles to Beijing – possible with plate tectonics. If you want to know what these several states of plate assembly can do for your world-building, make sure to come back for the climate part.

Novopangäa, Reiner Olzem

Novopangäa, die mögliche Zukunft der Kontinente. (c) Reiner Olzem (

Jigsaw worlds

If you look at the world map, you quickly notice that Africa and South and Central America fit together really well. Sure, the coasts look a bit different and everything is distorted, so it’s not exactly a perfect fit, but you know immediately that they did belong together some time ago. Other continents fit well together as well, though they have been separated a while longer, so have eroded more.

At the beginning of my geology studies I had planned to build a world from the very beginning. I want to continue this project together with you. Thus, here are the plates of my world. On this map, you notice that a few continents and islands fit together. Thalin, for example, still has this little peninsula that fits perfectly well into the East Coast of Fehnis. Sibenia, however, is just separating, while the islands of Werden and Taro could be assembled back into Fehnis’ and Kryos’ western coasts with a little effort.

Weltenbau: Die Kontinente

Building my own world – starting with some continents.

You can also see how the coasts don’t fit together perfectly. Parts are missing while others would be overlapping. That’s okay, because remember: The tearing apart happens over the course of millions of years, while the sea level rise (and fall) and coast erosion processes work much faster. Thus, I distorted some of the parts and made the coasts look a bit more natural.

And now, it’s your turn.


How to build yourself some continents

  1. Think about how many continents you need and in which size you would want them.
  2. Decide whether you want a bunch of smaller continents or one mega-continent. A little tip: When a supercontinent breaks apart, the temperature rises considerably as there will be a lot of volcanisms and thus CO2 in the air.
  3. Now scatter your continents across the world map.
  4. Pick which continents move towards each other and which move apart. How to the «sides» of your plates relate to each other?
  5. Shape the continents that move apart from each other so that they could fit into each other. The closer they are together the more they need to assemble each other. That doesn’t have to include each coast line. Just take a few of them and make them stand out enough that once could push them back together if they wanted to.
  6. At the boundaries where continents move against each other, we will start building mountain ranges. But more on that in part 2.

Little tip: Since the earth is round, your plates and continents should reappear in the same spot on the other side, when they reach the map limits.This isn’t true for any disc worlds 😉



P.S.: You can download the basic coordination system here.


Disclaimer: Of course, fantasy worlds do not have to follow our laws of nature and authors do not need to complete a geology course in order to build a working fantasy world. However, I hope you have fun and maybe I can sharpen your view a little.