Forming of worlds

[Umbran]

Q3. I should have said can land masses form regardless of plates, or are the shapes of plates and land masses directly linked (I found a map with the plates on it, so I can safely say no, am I right?)


New question, Q4. how are the shapes of landmasses "decided", if they are not at plate edges (Austrailia for example)?

Assumiing, of course, we're following a physical model akin to the real Earth...

"Land Masses" are merely the places where the surface is high enough to stick up above the water. So long as your planet isn't smooth like a cue ball, all you need to form a land mass is a sufficiently shallow sea.

Typically, the stone in a land mass is less dense than that of the sea bottom - I think hte leading idea is that during formation of the world, while things are still molten, the less dense material "floats to the top" as it would in any fairly fluid situation.

Now, if you have no plates, there's one small problem - erosion. There are two basic ways to get new land - volcanic activity (like in Hawaii) and tectonic uplift (like in mountain ranges). If you've got no plates, you've got no tectonic uplift. The land masses eventually erode away, and you're left with volcanic islands as your only land masses.

All of which you can ignore, of course, in a fantasy setting.

 

[adwyn]

It's rare, but sometimes a river is long-lived enough to stay in more-or-less one spot during the eons it takes for a mountain range to uplift. I forget what its called, but if the mountains uplift in a line crossing the river, the river will carve through them as they lift. I.e., the river stays on the same level, but the surrounding terrain lifts into mountains. It's kind of like canyon forming, except the terrain is going up leaving a trench with a river in it, instead of the river carving down and forming a traditional canyon.

Several things can account for a river flowing perpindicularly through a mountain range - besides the above, the most common causes would be rivers exploiting fault lines and glaciation.

Most fantasy worlds render this all of this moot by having relatively short geologic histories that leave little time for geologic change. Thus most edifices would need to have been created in toto. This is called confectionary geology - the appearance is what counts as everyhting is the same underneath.

 

[Desdichado]

Australia is a plate, it just borders against oceanic plates rather than other continental plates. Oceanic plates are typically much thinner but more dense than continental plates, IIRC.

 

[Ferret]

I'm not trying to be big headed but isn't the plate the Austrailasian plate? So what I mean was how come the country austrailia, looks like it does, even when it's in the middle of the austrailasian plate?

 

[MerakSpielman]

Not sure what you're asking, Ferret, but the main contentental plates aren't the only plates... they are themselves riddled with smaller and less active plates, forming faultlines, uplifts, etc...

 

[Numion]

Past glaciation is a common cause of areas that have a lot of lakes.

To see this effect clearly, check out a map of finland. The direction of glacialization (NW - SE) is clearly visible from the thousands of lakes we have here. The lakes are generally aligned in that direction.

Here's a link to a map, not perfect but gives some idea:

http://kartat.eniro.fi/query?what=m...ading_code=&company_name=&geo_area=&ns=&stq=0

(hope that works, it should add the URL tags automatically...

 

[MerakSpielman]

Cool! I do they bother naming all those lakes? After all, it looks like there are easily thousands of them.

 

[Ferret]

Wow! I didn't know that.

From the map I found It looks like a lot of the country's edges are on plate boundries, austraila (not the plate) isn't near a plate boundry. Shoot me if I'm wrong.

 

[MerakSpielman]

Tectonic stress map of Australia.

 

[Ferret]

How big can lakes get? When are they seas? Could a lake/sea be as big as mongolia?