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Thread: Realistic Geography

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    Question Realistic Geography

    I'd like the geography in my world to follow real world patterns, but I'm not really even 100% on the rules on Earth, lol. Does anyone have any resources I could use to this end?

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    Guild Master Gracious Donor Midgardsormr's Avatar
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    I find a good place to start to be Expeditious Retreat Press' free A Magical Society: Guide to Mapping
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    Software Dev/Rep Redrobes's Avatar
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    Quote Originally Posted by RoninFrosty View Post
    I'd like the geography in my world to follow real world patterns, but I'm not really even 100% on the rules on Earth, lol. Does anyone have any resources I could use to this end?
    I'm not sure anyone fully understands the rules. There are some pretty nifty climate modeling bits of software running on big machines and they cant seem to predict whats going on.

    Theres so many things to describe. We have talked about rivers a lot and how they are made and where they flow etc and theres no easy way to predict or describe that other than in simple terms like water flows downhill. Part of the issues are that much of the world is in balance where a number of factors adjust something which have knock on effects. Many political problems are caused from people desiring an outcome and making changes which they think will cause that outcome only to find that something unrelated and usually pretty catastrophic occurs too.

    So are we talking about global stuff, regional terrain, local effects or large scale stuff ? Rock, rivers or vegetation ?

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    Lots of affects to consider and not all of them are documented in any map.


    Wind, climate, rainfall, seismic activity, pollution all impact land in ways not shown on most fantasy maps - and we haven't even touched on Magic. With many elements not explained you have a larger capacity to make things the way you want and call it 'realistic' - some unseen force makes it so.


    You can make broad gestures - river flow always going down is a good one.

    Old areas typically have more erosion.
    Mountains next to trenches or canyons will probably be steep and young.
    Evergreens in the north, palms in the south.
    Seas are salty and deep. Rivers and lakes not so much.
    Islands form in chains like the top of a ridge.
    Coasts have a wild and random curve to them. They're best generated rather than drawn IMHO.

    Personally, I find a great deal of 'realism' is a sense best satisfied by a random element. I question my decisions if I draw a coastline but I feel much more confident with a generated one that I 'discover'. I think its just an unnatural act to make land.


    Sigurd

  5. #5

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    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 01:26 AM.

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    Software Dev/Rep Gracious Donor waldronate's Avatar
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    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.

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    /head a splode

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    Quote Originally Posted by Midgardsormr View Post
    I find a good place to start to be Expeditious Retreat Press' free A Magical Society: Guide to Mapping
    This was really helpful, thanks.

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    Guild Adept Valarian's Avatar
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    Quote Originally Posted by Sigurd View Post
    Evergreens in the north, palms in the south.
    Unless you're in the southern hemisphere, in which case it's the other way around

    Islands form in chains like the top of a ridge.
    Volcanic islands do. You can have island clusters caused by sea level rising and flooding low lying areas (e.g. UK, Ireland, Isle of Wight).
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    Guild Member Korba's Avatar
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    I'm in the process of writing a climate guide FAQ at the moment but i'm not that far along. Waldronate's post is a great summary though.

    One thing i would like to add is read about Hadley Cells. They define the genral bands of climate around the globe influncing the positions of grassland/forest/tundra/desert and tropical rainforest (then influnced by mountains and ocean patterns of course.

    Korba

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