IntroIn this tutorial, we are going to learn how to draw a map in the style of the image above in GIMP. While it may look daunting at first, the process will be broken down into a series of steps that are easy to follow. You can install gimp at gimp.org if you don't have it already. We will be drawing a continent with the size of Australia and the geography of South America.
Creating the imageOpen GIMP and create a new image with dimensions 400x300; we don't want to overwhelm ourselves at the start, and this should be enough for fitting a roughly Australian-sized continent. We are going to begin our map by drafting the plate tectonics of the region, and we'll assume the following for the map:
- Each pixel is 10km wide (and thus has an area of 100km2)
- The region has a similar atmosphere and gravity to Earth
- The region has similar plate tectonics to Earth
Before we start
Intro to plate tectonicsPlate tectonics are crucial for drawing geologically sound continents. They also are fairly fun to watch, and have many little quirks that lead to awesome geological formations. For instance, have you ever wondered how Turkey and Japan formed? They're both results of back-arc basins[W]: basically, Turkey and Japan were part of Eurasia until the subducting oceans around them ripped them off into the sea, forming the Black Sea and Sea of Japan respectively. There is a really awesome tool called EarthViewer that lets you see the geological evolution of the planet over its entire history. I recommend you play around with it to get a feel for plate tectonics.
Anyways, to start off, we're going to introduce our first reference map. While making plate tectonics, we're gonna pay close attention to this map so we can emulate how plate tectonics works on Earth. The map in question is this one (and it should look like the map on the right). If you're uncomfortable using such a big map you can find downscaled ones here. In the top left corner of the map you should see a key. Here's an explanation of what it all means:
- Continental / oceanic convergent boundary (purple): This occurs where two continental plates or two oceanic plates are colliding. This creates mountains.
- Continental rift boundary / Oceanic spreading ridge (red): This is when a plate is splitting apart. For example, the African plate once included the Arabian and Somalian plates, but they are both currently in the process of rifting off of Africa. And between South America and Africa lies the Mid-Atlantic ridge, which was once a continental rift much like how Africa is today, which grows wider and wider as the two continents move away from each other. This can also be known as a divergent plate boundary. It's important to note that this also creates mountains, perhaps counter-intuitively. This is because the rifting causes immense amounts of volcanic activity.
- Continental-oceanic transform fault (Green): This is when two plates are moving past each other and mountains aren't really created nor are they destroyed. However, there are plenty of earthquakes.
- Subduction zone (blue): Subduction zones are a special type of convergent boundary where oceanic crust "subducts" either under other oceanic crust or continental crust. This leads to a ton of volcanos, which form island arcs if it's subducting underneath oceanic crust, and mountain ranges if it's subducting underneath continental crust. Examples include the west coast of South America (the Andes) and the Aleutian islands.
Intro to elevationWe will be using two contours to make the map: a greyscale contour and a colored contour. Save the following images to your computer by right-clicking and clicking "Save-as":
To convert between the two types of contours we will use converter.jar, a simple tool that can parse an image and convert it between either type. We also will be using another reference map: the Earth elevation contour map. Save that to your computer as well. If you want a greyscale version, just use the converter. Easy, isn't it?