When creating any type of world dealing in a fictional environment that spans a large area, you need to do this first. Maybe not first, but it’s should be in the top five things you do first. The best example, is as always, the world around you.
Erosion is a big aspect of shaping the earth. Look at the Grand Canyon. Erosion comes from friction, and in this case, lots and lots of friction. Rivers will eventually create a little dip in the earth. Wind erodes less because it’s not a continuous force. It blows from one direction usually, but not constantly. If you have a large desert in your world, consider sandstorm erosion. If a city has been in a desert for a while, the buildings will have sand eroding at the buildings. Otherwise, sand doesn’t do much to other sand. Large rock formations in a desert give a majestic feeling, and a sense that your characters are small compared to the world. If that’s what you want. Current erosion in the oceans does a considerable amount to the shaping of continents, and the direction of your current shapes the coastline.
Mountains, and Tectonic Movement
Tectonic movement is what you learned in grade school, and never thought about again. Basically, the earth’s outer crust is broken into several large plates. If your story spans an entire world, you may have to plan out all of them, but with a single continent, you many need only one or two.
Mountains are formed by tectonic movement. These plates move against each other along fault lines, and landmass is just pushed up. The Indian plate is a good example of this. It moves north, and has formed the Himalayas. Another example is California, which has the Pacific plate moving north, and the North American moving south. This creates the rather small mountains along the California coastline, and consequently the Sierras.
This is the reason mountains are formed in ranges, and why Helgrind bugs me to no extent. If you have your continent, mentally map out tectonic movement so your mountains form realistically. Also note, fault lines don’t run through large places, they mainly surround landmasses. And, plates can only move in one direction, they don’t expand.
Gravity and Rivers
Water flows down. Stuff comes down, snow comes down. Rain and its various forms go down. It’s how the world works. Rivers generally come from two origins, snow on mountains, and lakes on a higher level than the rest of the world. Along the mountain, in the spring, snow melts into water, and it flows down. Or a lake that simply overflows, and water pours out. The best example of the last option is the Nile River, which flows north from Lake Victoria. If you’ve gone far enough to draw a map for your world, you can’t just make a wavy line from a mountain leading into a lake, or the ocean. Each turn in the river indicates the land around it. In effect, hills. Water is simply guided by hills or other large formations. Also, rivers in a similar area have to flow in the same general direction. Two rivers side by side flowing in opposite directions is very strange, and makes it feel forced, unless there might be a tall hill in between them. While you can have rivers slowly veer away in the direction you need them, it has to stay with the land formation. When examining rivers and lakes, imagine your map in three dimensions. The higher points are your mountains or hills, and coastlines are usually lower. So now imagine your rivers, and be sure they follow your rules.
Rivers, lead into other rivers, lakes, or the ocean. This is a simple concept, and easily grasped. Cities are also built along rivers, for trading purposes. Although rivers only flow in one direction, so your people with have to walk the other way.
Oceans are essentially giant lakes with too much salt. If you’re accepting the laws of physics, your planet will have poles. Not poles, poles. The frozen top and bottom where the sun can’t do its job properly. The ocean is maintained by the ice breaking off, and eventually melting. Oceans aren’t hard to recreate, but the stuff inside of can be.
Reefs, shoals, and shallow water are all nasty aspects of the ocean. Depending on how much emphasis on sailing you put into your story, the more you’ll want to plan these things out. Reefs are large constructs of coral and other stuff, and can wreak havoc on ships, especially wooden ones. Also, the closer you get to land, the shallower your water should be. While this isn’t true anywhere (nor should be, for realism), it dictates where your people will build port cities. No one wants to park their galleon two miles out because some idiot decided to start a port in shallow water. Shallow water hinders ships, and by extent, rocks. While a ‘Shipwreck Cove’ is overused, a simple passage between islands can provide this hindering aspect.
Islands, are islands. Little dabs of land in the ocean. Islands are made in a few different ways. Madagascar, if you’ve ever looked at it on a map, fits neatly into the side of Africa. So naturally, it broke away at some point in the past while the Earth was changing. While it won’t fit like that five thousandth puzzle piece, the general contour should be recognizable, because current erosion has changed it. Another island creation method is undersea volcanic eruption. The Hawaiian islands have a curve to them, as if they are being pulled off to the northeast. They are being pulled, by the Central Pacific current. Undersea volcanoes belch out earth and rock, and it floats up and hardens, and the water pulls it. This effect gives your world a natural movement.
Currents are flows of water. Take a look at a world map of currents for ideas, but currents also affect climate. Newfoundland in eastern Canada and Britain are nearly on the same parallel. Newfoundland is under snow for the majority of the year, but Britain got off easy with rain and fog. The North Atlantic current is the answer. Water from the equator is warmed, and carried upward past Spain, Portugal, and Britain. it goes up around Greenland, and is cooled again, then flowing back down along Canada and the Eastern seaboard. Currents have a major effect on climate, and vicariously, on your civilization. A quick note: Warm water from the equator flows naturally to the poles, and the cold water from there moves back towards the equator, and becomes warm. This should be a simple guideline if you’re thinking about currents. Sail ships use currents all the time in the absence of a tailwind. Many times detours would be taken to follow currents.
Wind is formed by air currents. Warm and cool currents spiral horizontally and creates wind. The direction wind comes from is an important factor. A wind coming through a desert onto a coastal town will give warm air during the day, and unnaturally cool air at night. A wind coming from a snow capped mountain range will be cool year round.
To be continued.. I’ve been sitting down for too long.