Oh my. To bring my 2 cents into this, I often search the Earth map for similar features than my own work. It's nice to see such simple guidelines
Oh my. To bring my 2 cents into this, I often search the Earth map for similar features than my own work. It's nice to see such simple guidelines
I'm also interested in this. What forms weather patterns? What about plate tectonics? What about currents in oceans? I've heard having large oceans like several maps do would cause gigantic storms raging across the globe....
Last edited by Kestenvarn; 03-12-2009 at 12:26 AM.
Weather is caused by uneven heating of the earth by solar radiation. This uneven heating causes air masses to move. The amount of heating of a given area and the change over time are controlled primarily by the axial tilt of the planet, year length, the size of the planet, the rotation speed of the planet, and atmospheric density. The axial tilt and year length determine the seasons and the min/max possible temperature in an area. Differential heating between the equator and polar regions causes flow of air toward and away from the poles. The size and rotation speed of the planet cause that poleward flow to be deflected to the side, causing the spin that shows in large storm systems. Atmospheric density determines the total energy that can be carried by a parcel of air.
Clouds form when water is evaporated from wet areas, rises, and begins to condense in the upper reaches of the atmosphere. Storms (great masses of clouds) occur when a body of (typically warm) moist air encounters a mass of cooler air. Storms generally gain moisture over bodies of water and lose it over land (more quickly over drier land such as desert compared to woodland or jungle). Larger oceans potentially allow larger storms to form but there is an upper limit dictated by atmosphere and world characteristics.
Surface ocean currents broadly follow atmosphere dynamics. Deep ocean currents follow the same sorts of rules as the atmosphere, but with the added factor that salinity has a major impact in addition to heat (saltier water is heavier than less salty water of the same temperature; warmer water is lighter than colder water). The Gulf Stream, for example, arises in part because cold water sinks just north of Iceland, pulling in saltier water from the tropics, which gets colder and sinks, pulling in more water, and so the current flows.
Plate tectonics arises due to differential heating in the mantle from the core of the planet. Hot rock rises and cold rock sinks. The continents are formed of much lighter rock than the mantle rocks and so float around, following the mantle currents. Then continents collide, mountains tend to form in the collision zone (see the Andes and Himalaya for excellent examples). When plates pull apart, oceans form (see the Atlantic ocean and the new ocean forming in the Red Sea / Africa Rift Valley). The hot rock that rises from the mantle tends to take the form of relatively small plumes. These hot spots break through the crust in relatively small areas. The motion of the plate moving over them can be seen from the action of the hot spot on the plate rock (see the Hawaiian island / Emperor seamount chain and the Yellowstone hotspot / Snake River Valley in the US). The mountains pushed up by collisions tend to be near the edges of plates. They start high (Andes / Himalayas) and erode down over time (see the Appalachian and Ural mountains). Alluvial plains are formed from erosion products of mountains (the great plains of the US are formed from debris from the Rocky Mountains and Appalachian mountains with a bunch of gunk scraped off Canada during the last ice ages).
OK, that's enough intro to geography for now. There are lots of great textbooks out there on this subject and many good college class websites. Physical Geography is what you're looking for.
Sorry about the long-winded spewing but sometimes I can't help myself.
/head a splode
Don't worry about getting too accurate. I studied world models and information for nearly 8 months in order to make the world I was working on realistic. Even after all that I still don't know even a fraction of everything there is to it. It did however teach me something important. Verisimilitude trumps realism when it comes to fantasy worlds.
Don't worry about getting it perfect, instead get yourself a good set of simple rules to use as a measuring rod. There are quite a few decent rules of thumb that you can remember. Doing so will make things alot easier. Even these have alot to them but they are alot easier then full blown research. Here's a fair bit to get you started.
- Mountains form where plates collide (Himalayas), where one plate subducts under another (Cascades), or where a hotspot burns through the crust (Hawaiian Isles).
- The younger the mountain the more jagged its peak. Young mountains such as the Rockies are tall and sharp. Old mountains like the Appalachians are short and curved due to erosion.
- Rivers start high and flow with gravity, always flowing along the path best able to carry them (generally the steepest one).
- Rivers come together, they don't split apart. They might break up around obstacles or meander through different paths over time, but these breaches are rarely longer than a few hundred feet to a mile or two with the river quickly resuming a single course.
- The only time a river doesn't meet is when the above happens right as it hits the ocean. If it meanders a bunch you can get a river delta at the mouth.
- The style of the river depends on the terrain. Fine sand and silt tends to create meandering rivers that have lots of switchbacks and oxbow lakes (the Mississippi) while rocky ground creates fast flowing, straight rivers (the Columbia).
- Deserts are formed where there is little precipitation falling. This happens mostly due to barricades that the moisture can't overcome. Rain shadows for example are a physical barricade. A mountain range blocks rain from reaching the other side and a desert forms. Other barricades exist such as prevailing winds pushing the moisture out to sea or very cold temperature that lowers the atmospheric ability to hold water. The final primary barrier is one that is often overlooked. Simple distance. Moisture can only stay airborne for so long before it comes down. That is why the interiors of large landmasses tend to be dry.
- Barriers divide groups as well as weather. People on the east side of a mountain range are probably going to be very different culturally than those on the west side. An animal on an island is going to be different then its cousin on the nearby mainland if neither can travel over or through the water separating them. Again large distances are a viable barrier.
There is of course much more to learn, but just keeping a simple library of important facts will allow you to make acceptable worlds.
My Map Portfolio
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Unless otherwise stated, all my work is licensed under a Creative Commons Attribution-Noncommercial 3.0 United States License.
I've written some tutorials about topics such as climate, shore lines, rivers, etc. specially aimed at people who want to draw quite realistic maps.
I'm a geologist, so I have few problems to do it 'realistic', but some people I know had quite some problems, so I started to write those tutorials.
The only problem is, they're all written in German, but if you're interested I could try to translate them, though it might take some time and some proofreaders will probably be needed.
I'd be glad to proofread, if you translate them.some proofreaders will probably be needed.
Both of my main programs are free! Find them here:
SketchUp 7
Kerkythea
Note that you need a SketchUp to Kerkythea exporter, which can be found on the Kerkythea website.
Given science still hasn't quite figured it all out, it's safe to say that most of us will not hold it against you if you don't either. The world is incredibly complex and would take far more computing power than I believe all of the members here have combined. Using simple generalizations as mentioned before will get you pretty darn close though. Saying "water flows down hill" and putting it in practice creates good results, but the reality is that water takes the path of least resistance, it's sooner go through loose sand than solid granite. I'm content to use erosion simulation in Wilbur even knowing runs as if the entire planet is composed of the same material.
I'll concur that Waldronate has a great summary of the basic forces at work in a world, and feel free to get as complex as you like. New, and fascinating, techniques arise when people seek to go beyond the norm.