How to get a world with polar seas

[Technomancer]

How would a world that was completely dry except for a large sea at each pole be formed?

By my admitedly limited knowledge of how these things work, I would start with a frozen world covered in ice with the highest elevations at the equator gradually sloping downward to the poles. Cue solar flare or shift in orbit or something that makes the planet a lot hotter, ice melts and flows toward the poles, leaving a big dry expanse between the poles (with maybe isolated lakes or small seas somewhere between. Logical? Possible?

 

[Pbartender]

How would a world that was completely dry except for a large sea at each pole be formed?

By my admitedly limited knowledge of how these things work, I would start with a frozen world covered in ice with the highest elevations at the equator gradually sloping downward to the poles. Cue solar flare or shift in orbit or something that makes the planet a lot hotter, ice melts and flows toward the poles, leaving a big dry expanse between the poles (with maybe isolated lakes or small seas somewhere between. Logical? Possible?

Absolutely.

You don't even need the solar flare/orbit shift... Just start the planet out that way. There's nothing inherently wrong with that particular geological arrangement.

 

[Bayushi Seikuro]

How would a world that was completely dry except for a large sea at each pole be formed?

By my admitedly limited knowledge of how these things work, I would start with a frozen world covered in ice with the highest elevations at the equator gradually sloping downward to the poles. Cue solar flare or shift in orbit or something that makes the planet a lot hotter, ice melts and flows toward the poles, leaving a big dry expanse between the poles (with maybe isolated lakes or small seas somewhere between. Logical? Possible?

Now, first off. I'm not an expert at climate shifts, or anything.

I don't know that it'd be possible to have seas at BOTH poles. It's my understanding that the reason lakes and rivers form would be the grinding of the glaciers. It's how the Great Lakes formed; as the glaciers retreated, the ice gouged up the earth, leaving giant 'vats', more or less, to be filled in by the runoff water.

So, at least with my understanding, I would think to have giant basins form at a pole, an easy explanation, if you wanted science for the world, might be a meteor crashed into the pole; that'd provide the axis shift, create a giant bucket to catch drainage, and melt a lot of water.

Just some random thoughts. Hopefully they help get your thoughts in the right direction you want to go.

 

[Rel]

I'd think with a larger axial tilt than earth's then you could get enough sunlight at the poles without having to make the entire planet really hot. Higher elevations at the equator doesn't seem that far fetched to me either since centrifugal forces tend to make planets that spin somewhat oblate at the equator anyway. But I have no idea what implications plate tectonics have on that over time. They might tend to smooth that out.

 

[Technomancer]

Now, first off. I'm not an expert at climate shifts, or anything.

I don't know that it'd be possible to have seas at BOTH poles. It's my understanding that the reason lakes and rivers form would be the grinding of the glaciers. It's how the Great Lakes formed; as the glaciers retreated, the ice gouged up the earth, leaving giant 'vats', more or less, to be filled in by the runoff water.

So, at least with my understanding, I would think to have giant basins form at a pole, an easy explanation, if you wanted science for the world, might be a meteor crashed into the pole; that'd provide the axis shift, create a giant bucket to catch drainage, and melt a lot of water.

Just some random thoughts. Hopefully they help get your thoughts in the right direction you want to go.

Meteor, eh? That could create the lower elevation at one of the poles, shift the orbit...and create a supernatural cataclysmic event for the superstitious natives to base their calendar on. Very nice.

 

[Technomancer]

I'd think with a larger axial tilt than earth's then you could get enough sunlight at the poles without having to make the entire planet really hot.

That's sort of what I wanted though, a decent climate at the each pole with a vast mysterious desert wilderness between them.

 

[Warehouse23]

Polar oceans with equatorial plains is a perfectly reasonable planetary configuration (near as I can figure--yes, I am a planetary geologist, no, I have not had my coffee yet). Rather than relying on a large tilt in the planet's axis (obliquity), you could imagine a very warm planet (close to its star), with low obliquity, making the poles the only location where large bodies of water are stable (the equator is too hot, and the atmosphere too dry). Could such a planet be stable over the long run? Hard to say. Does it make a compelling setting--sure!

 

[Ahrimon]

I think your world would be a bit more ovoid in shape than the average planet. It's been a while (and I could be completely off base on this) but I recall that water favored flowing toward the equator. Part of how centrifical force from the earth turning pulls things that way. Geography plays a major factor though.

 

[dougmander]

Topographically, there's nothing inherently farfetched about having seas at both poles. The problem is having temperate poles and a cold equator. It's really hard to see how a planet would be cold at the equator and hot at the poles, but here are some nearly-plausible scenarios, maybe just enough to suspend disbelief for a fantasy world:

1. Volcanic hot spots at the poles that keep them warmer
2. A torus of debris around the planet's equator (maybe a destroyed moon) that reduces insolation at lower latitudes but doesn't affect the polar regions
3. Extremely high plateaus or mountains at the equator, like a belt encircling the planet (think 10,000 Kilimanjaros or a vast Tibetan plateau)
4. The planet has an axial tilt of 90 degrees, with one pole pointed at the sun, and the other at a "hot jupiter" companion star. So the poles are always "noon", and the equator, twilight.
5. Equatorial volcanoes that constantly barf out ash into the stratosphere, circling the equator like a belt and cooling lower latitudes.

Rel's suggestion for a large axial tilt would actually make each hemisphere a dark, frozen wasteland for half a year, and bathed in dazzling sunshine for half a year. Just like our own polar regions, but covering a larger area and more extreme.

Go to this website for some amazing sculpted globes and maps of alternate Earths:

http://www.worlddreambank.org/P/PLANETS.HTM

 

[Pbartender]

The problem is having temperate poles and a cold equator.

He doesn't want it cold at the equator... He wants it temperate and wet at the poles, and very dry (temperature irrelevant) at the equator.