World-Building Geography Help: Polar Seas

[Sado]

I need some help from you geography whizzes out there designing my homebrew setting.

Here's the basic idea: Imagine a Mars-type planet, a big cold desert with icecaps at the poles. Now imagine it's a lot hotter-instead of icecaps there is a small ocean at each pole, and a hot desert in the middle latitudes instead of a cold one. Civilization is clustered in temperate regions around the polar oceans, getting sparser the farther toward the equator you go. The middle latitudes I see as being inhabitted by reptilian creatures and other hardier species that could survive such a climate.

What would the climate of such a world be like? What kind of geography would it have? Could this type of world even support life, much less civilizations?

I have been wanting a ring of mountains around the inhabitted areas to ensure a decent amount of rain for them. Is this something that would/could logically occur? Would mountain ranges form parallel to the oceans or perpendicular (or both/either)? If so, would it go straight from temperate between the oceans and the mountains to desert once you pass the mountains? Would there be jungles, savannah regions, or rain forests, or would it go straight from temperate to desert? Would there be any significant bodies of water between the mountains and the equator?

 

[AdmundfortGeographer]

The thing to keep in mind is that water doesn't just end up collecting where it is temperate or cold. And ice packs on planets accumulate generally not because there is a lot of snow fall, but because there is never a season when it reaches above freezing. Meaning that an inch or two of snowfall, over tens of thousands of years, just adds up.

But if you want polar seas with no water bodies between the two, you simple need to have the lowest elevations be at the poles. After all, water runs down hill. Water will enter the atmosphere by evapo-transpiration, and winds and convection could carry it anywhere else in the planet (generally) over time.

True, mountains are the best way to force water out of the atmosphere into rain or snow. But it is true that water collects at the lowest elevation, this is where a planet's seas and oceans are. You could conceivably have dry seabeds in the desert portions of the planet, but you can't have these be linked to either of the polar seas. The polar seas would have to be their own basins. Otherwise, water from the polar sea would have just flowed out to where the lower latitude seas were losing water to evapotranspiration... water will level itself out.

You might want to consider the polar seas being indented with peninsulas and dotted with islands. These peninsulas and islands, with modestly high hills or mountains in them, could catch rainfall from the wind coming off the water.

A major issue with life at those polar latitudes will be the height of the sun in the sky. It is conceivable that some mountains could cast shadows for tens of miles for entire seasons in length. Assuming this planet you have here is like Earth in that its axis of rotation is tilted, allowing the sun to be always in the sky during one long part of the year, and the sun is set for the another long part of the year... you will have even more challenges that civlizations would have to overcome. Vegetation would have a hard time surviving there, so many civilizations would locate on the equator-facing slopes of hills or mountains just to grow crops. The civlizations would also probably grow crops like mad until the season of the sun's disappearance comes, when they would have to rely on stocks of their grown crops, and to hunt or fish exclusively. Or maybe have to experiment in subterranean agriculture, mushrooms for example...

And mountain ranges do not form according to water. Mountain ranges almost always are occuring where two tectonic plates collide (Andes and Himalayan mountains), or had collided in the past (Appalachian and Ural mountains). Another way mountains have formed is over volcanic hot spots, locations where a continuous plume of hot magma wells up from the mantle in the same place for a long time. The Hawaiian islands are such an example, Iceland is another, The Black Hills formed this way as well. Notice though, volcanic "ranges" are small in comparison to tectonic collisions. Really, about Iceland, it is forming where two tectonic plates are pulling apart, allowing magma to rise up in the gap... this is different that Hawaii's formation, which is of a tectonic plate sliding over a plume, and the plume simple pushing magma right through the plate.

So, small rings of mountains is unlikely. But maybe you should read up on the Fergana Valley in central Asia. Here is a good map. A fertile valley, along the old Silk Road, in the middle of a vast arid expanse. Totally conceivable that cilizations could grow up in these kinds of locations. The Fergana Valley is situation in such a way that wind is funneled into the vast valley, where it then ends up depositing what little water there is in the air in the mountains above the valley.


Anyway, just some ramblings of a geographer to consider.

 

[BSF]

Wow, a lot of possibilities there. The short answer is that any of those things are conceptually possible. The long answer comes down to how you model your world.

Size, distance from the sun, whether you use plate-tectonics, etc. I don't know if I could give you a quick answer. I would suggest Expeditious Retreat Press' Magical Society: Ecology and Culture. It has most of the information you are looking for and is more accessible than a Physical Geography textbook.

One thing to remember that the definition of a desert is a lack of yearly precipitation. I live in a high altitude, temperate desert. Albuquerque is situated on the west side of the Sandia mountains (Part of the greater Rocky mountain chain). Prevailing rainfall comes up from the Gulf of Mexico and most of the moisture gets dumped on the east side of the mountains as the air rises to clear the Sandias. Temperature wise, we are no warmer than the Dallas area, but it is a dry heat.

There are arctic deserts down in antarctica where they get very little precipitation but it is very cold and there is a bunch of ice around. Deserts come in many different forms, as do rain forests. So be sure you understand why something is a desert when you start world building.

 

[Sado]

But if you want polar seas with no water bodies between the two, you simple need to have the lowest elevations be at the poles.

How would this occur? Any special requirements?

True, mountains are the best way to force water out of the atmosphere into rain or snow. But it is true that water collects at the lowest elevation, this is where a planet's seas and oceans are. You could conceivably have dry seabeds in the desert portions of the planet, but you can't have these be linked to either of the polar seas. The polar seas would have to be their own basins. Otherwise, water from the polar sea would have just flowed out to where the lower latitude seas were losing water to evapotranspiration... water will level itself out.

What would happen to water that flowed down the equator side? Normally I guess they would form small seas or even oceans. But what it was really hot-like boiling point hot? Would it be possible for that much of a temperature difference to exist between the equator and pole sides of the mountain range? Or if it wasn't up to boiling, I guess there would be water on the equator side, but it would be really hot.

A major issue with life at those polar latitudes will be the height of the sun in the sky. It is conceivable that some mountains could cast shadows for tens of miles for entire seasons in length. Assuming this planet you have here is like Earth in that its axis of rotation is tilted, allowing the sun to be always in the sky during one long part of the year, and the sun is set for the another long part of the year... you will have even more challenges that civlizations would have to overcome. Vegetation would have a hard time surviving there, so many civilizations would locate on the equator-facing slopes of hills or mountains just to grow crops. The civlizations would also probably grow crops like mad until the season of the sun's disappearance comes, when they would have to rely on stocks of their grown crops, and to hunt or fish exclusively. Or maybe have to experiment in subterranean agriculture, mushrooms for example...

What if it wasn't tilted on its axis? Would that mean no change in season ever?

And mountain ranges do not form according to water. Mountain ranges almost always are occuring where two tectonic plates collide (Andes and Himalayan mountains), or had collided in the past (Appalachian and Ural mountains). Another way mountains have formed is over volcanic hot spots, locations where a continuous plume of hot magma wells up from the mantle in the same place for a long time. The Hawaiian islands are such an example, Iceland is another, The Black Hills formed this way as well. Notice though, volcanic "ranges" are small in comparison to tectonic collisions. Really, about Iceland, it is forming where two tectonic plates are pulling apart, allowing magma to rise up in the gap... this is different that Hawaii's formation, which is of a tectonic plate sliding over a plume, and the plume simple pushing magma right through the plate.

What would cause plates to collide in such a way that a ring of mountains would form around the highest 30-ish degrees of latitude? Would volcanic activity be more likely to produce this effect, like a huge Ring of Fire?

Size, distance from the sun, whether you use plate-tectonics, etc. I don't know if I could give you a quick answer.

What would a world without plate tectonics be like? How would mountains form? Just by volcanic activity?

 

[Sado]

As an aside, suppose we forget about the big mountain ranges surrounding the poles. Could we just have a world where the equator is simply at a higher altitude than the poles around the entire circumference of the planet? There could be mountain ranges between the poles and equator with water running off of them in any and all directions, but the gradual slope from equator to poles would cause all water to eventually run into the polar seas.

This would still allow for a desert region around the entire equator. But how likely is it that the equator would be higher than the poles all the way around?

 

[Gez]

How would this occur? Any special requirements?

It happens naturally, because of inertia and the Earth's rotation (which create the phenomenon called "centrifugal force", even if it's a misnomer to call it a force). The equatorial diameter is longer than the polar axis diameter.

But given that water is "morphic" than rock (that's why sea tides have more amplitude than earth tides), that will not necessarily help you.

 

[Pbartender]

But how likely is it that the equator would be higher than the poles all the way around?

Just as likely as any other planetary configuration.

Take Mars as an example. Due to past goelogic activity, the northern hemisphere of Mars is almost uniformly at a lower elevation than the southern hemisphere. Were you to fill Mars partway up with water, it would look something like this...

Notice how the northern half is one giant ocean, while the southern half is one immense continent. The only water in the southern areas is a result of meteor impact craters collecting water into lakes and inland seas.

In other words... Build the world the way you want it to look. I doubt anyone will question the geologic validity of the world; if they do, science can always come up with an answer later.

 

[AdmundfortGeographer]

How would this occur? Any special requirements?

Not really, you can just say the planet has formed "just so" that the lowest elevations were at the poles. It depends on how much real-world astronomy you want to put in to it, say, maybe the two poles had attracted major meteor impacts more than elsewhere on the planet 100s of millions of years in the past. You could make up whatever reason that was the case.

What would happen to water that flowed down the equator side? Normally I guess they would form small seas or even oceans. But what it was really hot-like boiling point hot? Would it be possible for that much of a temperature difference to exist between the equator and pole sides of the mountain range? Or if it wasn't up to boiling, I guess there would be water on the equator side, but it would be really hot.

Well, water will always flow so as to level itself. So if the equator was evaporating everything like mad, water will still continually flow that way. An issue is that you would want there to be enough replenishmant of the polar oceans' volume to equalize with the evaporation at the equators. Not likely. Can you imagine the amount of constant rainfall to compensate? Whew! So you would be best served saying that the polar oceans were simply isolated by elevation.

What if it wasn't tilted on its axis? Would that mean no change in season ever?

Correct, no seasons. Instead a worry would be that mountains at the poles would cast shadows dozens of miles long (the sun is close to the horizon at its highest after all). Not as problematic to civilizations as seasons of total sun and total darkness. Indeed, civilizations might build irigation systems to bring water from the dark sides of the mountains around to the life-favoring side.

What would cause plates to collide in such a way that a ring of mountains would form around the highest 30-ish degrees of latitude? Would volcanic activity be more likely to produce this effect, like a huge Ring of Fire?

You could just say that "coincedentally" it happened just so. In fact, yeah, it would be like the Pacific Ocean's Ring of Fire. You would probably want the mid-latitude plates to be subducting under the polar plates. Over geologic time, plates that are subducting under are other plates that will eventually disappear. We're talking geologic time here though...

What would a world without plate tectonics be like? How would mountains form? Just by volcanic activity?

Without plate tectonics? Well, some astronomers believe that earth planets with no tectonic activity are "dead" planets. Tectonics, and the vulcanism this process creates, is believed to have been necessary to the creation of composition of the atmosphere as we know it. Gases released by vulcanism and tectonics created the early atmosphere that made proto-life possible on earth.

An idea that I considered. As you want a ring of mountains right at the appropriate latitudes. You might want to consider a gigantic impact crater at each pole. I know, the statistical chance for this to happen exactly at both poles would be unreal.

You could say the planet's past civilizations earned the wrath of the gods who sent two planet killer meteors, one at each pole simultaneously. The impacts would create the exact geologic features you want, and potentially caused the enirvonmental change that made a desert of the whole planet. Thousands of years later, whatever water wasn't thrown into space by the impacts would have settled in the gigantic craters at the poles. Civilization of the remarkable survivors would then rebuild anew.

I'm stretching the believability of this option, of course. But it could be cool! Anyway. The continent of Taladas on Krynn of the Dragonlance is an example. Just make the meteor(s) bigger, and strike the poles.

Another option to contemplate, there was a Spelljammer accessory... Something Planetology...

There was one example planet that had one pole aimed directly at the sun eternally. An interesting idea. One half of the planets was an eternal desert sun, hot enough that fire elementals were comfortable... many hundreds of degrees above freezing. The other side was eternally dark, colder than the coldest layer of the Abyss... hundreds of degrees below freezing. However, right along the equator was a narrow ribbon of "livable" ground where the sun was perpetually at dusk/dawn. Here civilization exists in a temperate band. Occassional unpredictable storms of oven-hot air blows in, and occassional blasts of unpredictable "arctic" air come through, but generally would keep temperately mild. Of course, you're not going to get "polar seas" but it's a similar concept in some ways...


Dunno if any of this is much more help, but there you go.


Regards,
Eric Anondson

 

[buzz]

What would the climate of such a world be like? What kind of geography would it have? Could this type of world even support life, much less civilizations?

I have been wanting a ring of mountains around the inhabitted areas to ensure a decent amount of rain for them. Is this something that would/could logically occur? Would mountain ranges form parallel to the oceans or perpendicular (or both/either)? If so, would it go straight from temperate between the oceans and the mountains to desert once you pass the mountains? Would there be jungles, savannah regions, or rain forests, or would it go straight from temperate to desert? Would there be any significant bodies of water between the mountains and the equator?

Here's my best answer to all your questions, and you're probably going to hate it:

Yes, if that's what you want.

Seriously, you're creating the world. It can work however you want it to work. Real-world geology and tectonics don't matter, unless the party is comprised of geologists and adventures are going to focus on taking core samples.

The PCs aren't looking down on your world like a map. They're in the thick of things, wondering where the next tavern is. IMO, fleshing out that tavern is way more important than making a geologically-realistic map.

I will now get off my soapbox. Apologies for the diversion.

 

[tarchon]

Plate tectonics per se seems to be somewhat rare among planets, but non-plate-oriented tectonic activity is fairly common. The main implication of not having plates seems to be that mountains, volcanoes, earthquakes, etc. aren't as prone to forming large bands over the surface.
For your world, I think it would make perfect sense to have two large plates capping the poles with "transform" motion against the lower latitude plate/plates, where they slowly rotate relative to the rest of the crust, and you could probably even half justify that as the result of latitudinal bands of magma circulation in the core. We really have a similar situation with the Antarctic plate on Earth.