Intro
In 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 image
Open 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 tectonics
Plate 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 elevation
We 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?
Drawing the map
Now we're going to start actually drawing the plates. At the resolution of 10km/px, we should be able to fit in a continent around the size of Australia
on our 400x300 image (create it if you haven't already!).
- Take the Pencil tool, and set the width to 4 and the color to blue. Next, create a new
layer.
- Draw a nice, long stroke that goes from somewhere near the top to the bottom of the image.
This is a subduction zone, and it will be where we put the main mountain range.
- Next, draw two green strokes to the sides of the subduction zone to roughly the other edge of
the image. These are transform faults, and though they really a mix of red and green, we're going to approximate them all
as green.
- Now, to complete the plate draw a red line from the end of the top green line to the bottom
green line. This is the spreading ridge; the continent that we are drawing very recently broke off of another continent and
has begun to drift westwards.
- Now we're going to outline the mountain ranges and hills of this continent. We're not going to actually draw its outline
yet - that can come after this. Create a new layer and change the color of the pencil to brown.
We're going to first draw the long, spiny mountain range on the west coast (that has arisen as
a result of subduction). Make it spiny but also make it wide at some point (for a plateau).
- Since our continent just recently broke off of another continent (and rifts form mountains), we're going to add some hills
to the eastern coast of our continent as well. We're going to model our hills off of the Brazillian plateau, which means they'll
be somewhat low but very widespread across the continent.
- Now we're ready to begin outlining our continent. We're not going to outline the coastline, but rather the continental shelf.
Think of a continent as a plateau in the ocean - the continental shelf is the top part of the plateau, right before it drops off
into the seabed. Take a look at the lightest ocean color in the elevation reference map - see how things rapidly drop off to
the darker colors near its edge?
To do this, create a new layer and change the brush color to a nice, light blue that
is distinct from your other blue. Cyan works well for this. Follow closely your mountain ranges on your west and east coasts, but feel
free to do whatever you want with the top and bottom coasts - just make sure to keep it somewhat blobby.
- Now, our continent is more or less ready for some contouring. First, we want to create a new layer and paint it solid black, but we want to also make it
slightly transparent so that we can see the layers underneath.
Then we want to take our color picker tool and select the color of the 0-250m contour, aka "sea level." Optionally, you can copy
your contour key and put it in your image. This will require resizing either the key or the image (I resized the key, as I'm trying to keep a standard image size for this tutorial. However, I recommend you
resize your image to fit the contour key, as it looks cleaner.)
What we want to do next is to carve out our continent from the continental shelf we have. Stick very closely to the shelf in mountainous regions
and feel free to dig in a bit in flat regions. I may have dug in a bit too much myself, but I felt like making things interesting.
Take the Pencil tool, and set the width to 4 and the color to blue. Next, create a new
layer.
Draw a nice, long stroke that goes from somewhere near the top to the bottom of the image.
This is a subduction zone, and it will be where we put the main mountain range.
Next, draw two green strokes to the sides of the subduction zone to roughly the other edge of
the image. These are transform faults, and though they really a mix of red and green, we're going to approximate them all
as green.
Now, to complete the plate draw a red line from the end of the top green line to the bottom
green line. This is the spreading ridge; the continent that we are drawing very recently broke off of another continent and
has begun to drift westwards.
Now we're going to outline the mountain ranges and hills of this continent. We're not going to actually draw its outline
yet - that can come after this. Create a new layer and change the color of the pencil to brown.
We're going to first draw the long, spiny mountain range on the west coast (that has arisen as
a result of subduction). Make it spiny but also make it wide at some point (for a plateau).
Since our continent just recently broke off of another continent (and rifts form mountains), we're going to add some hills
to the eastern coast of our continent as well. We're going to model our hills off of the Brazillian plateau, which means they'll
be somewhat low but very widespread across the continent.
Now we're ready to begin outlining our continent. We're not going to outline the coastline, but rather the continental shelf.
Think of a continent as a plateau in the ocean - the continental shelf is the top part of the plateau, right before it drops off
into the seabed. Take a look at the lightest ocean color in the elevation reference map - see how things rapidly drop off to
the darker colors near its edge?
To do this, create a new layer and change the brush color to a nice, light blue that is distinct from your other blue. Cyan works well for this. Follow closely your mountain ranges on your west and east coasts, but feel free to do whatever you want with the top and bottom coasts - just make sure to keep it somewhat blobby.
To do this, create a new layer and change the brush color to a nice, light blue that is distinct from your other blue. Cyan works well for this. Follow closely your mountain ranges on your west and east coasts, but feel free to do whatever you want with the top and bottom coasts - just make sure to keep it somewhat blobby.
Now, our continent is more or less ready for some contouring. First, we want to create a new layer and paint it solid black, but we want to also make it
slightly transparent so that we can see the layers underneath.
Then we want to take our color picker tool and select the color of the 0-250m contour, aka "sea level." Optionally, you can copy your contour key and put it in your image. This will require resizing either the key or the image (I resized the key, as I'm trying to keep a standard image size for this tutorial. However, I recommend you resize your image to fit the contour key, as it looks cleaner.)
What we want to do next is to carve out our continent from the continental shelf we have. Stick very closely to the shelf in mountainous regions and feel free to dig in a bit in flat regions. I may have dug in a bit too much myself, but I felt like making things interesting.
Then we want to take our color picker tool and select the color of the 0-250m contour, aka "sea level." Optionally, you can copy your contour key and put it in your image. This will require resizing either the key or the image (I resized the key, as I'm trying to keep a standard image size for this tutorial. However, I recommend you resize your image to fit the contour key, as it looks cleaner.)
What we want to do next is to carve out our continent from the continental shelf we have. Stick very closely to the shelf in mountainous regions and feel free to dig in a bit in flat regions. I may have dug in a bit too much myself, but I felt like making things interesting.