higher pergentage of land?

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higher pergentage of land?

Post by k1234567890y » Sat 28 Apr 2018, 09:51

While I myself am not a fan of having a higher percentage of land in respect of the ocean on an Earth-like planet, it sems that some people prefer to have a higher percentage of land in their conworlds e.g. 1:1 or even more land than ocean. But I wonder if a higher percentage of land would actually create a higher percentage of dry or semi-arid areas, if so this might end up destroying the purpose of increasing the percentage of land on a planet(I guess people give more lands because they want more rooms for civilizations)...

What do you think? Will the increment of the percentage of land create a higher percentage of dry and semi-arid lands on a planet?
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Re: higher pergentage of land?

Post by Ànradh » Sat 28 Apr 2018, 11:37

It depends on the distribution of the land, but, generally speaking, that's true.
That said, arid and semi-arid regions are capable of supporting larger populations of people than the equivalent surface area of ocean. If the goal is more people/civilisations then that's the best strategy.

When I made my map, I didn't even consider this; my land masses are semi-random in shape and size, and the biomes etc. were determined after the fact.
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Re: higher pergentage of land?

Post by k1234567890y » Sat 28 Apr 2018, 13:19

ok thanks (: as after all humans are land-dwelling?
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Re: higher pergentage of land?

Post by Salmoneus » Sat 28 Apr 2018, 16:08

Humans are generally land-dwelling, yes.

And yes, naturally, smaller oceans means more land farther from the sea, which means less rain, which means drier.

But it's interesting to ask: when might that not be the case? Could you have a planet with a lot of land, without aridity?

Well, to have low aridity, you need one of two things: high precipitation, or low evaporation. The former makes the land very wet - it's why we have rainforests. The latter doesn't make the land very wet, but it stops it from getting very dry - it's why the semi-arid grasslands turn into dense forest as you go further north.

Let's look at the first option: high precipitation. To get precipitation, we need air filled with water, and then a decrease in temperature that reduces the amount of water the air can hold, so that the water falls out. The air is essentially a sponge - it picks up water that evaporates over bodies of water, and it gradually gets squeezed over land. Areas are arid because the water has all been squeezed out by the time the air gets to them.

So, again, this gives us two options: move the land closer to the sea; or get a bigger sponge.

The first: land closer to sea. Instinctively, less sea means less land near the sea. But not necessarily! A lot of earth's sea is a long, long way from any land, and a lot of it isn't even located under winds that are headed toward the sea. Which suggests: we could get rid of a lot of sea with minimal effect on aridity, provided that we got rid of the 'useless' bits of sea. In particular, sea in the tropics, where high temperatures and low pressures (ie rising air) make for a lot of evaporation and precipitation, is more 'useful' than sea in the desert latitudes, where high pressures (ie falling air) lead to little precipitation OR evaporation. In other words, you could whack a massive mega-Australia desert continent in the middle of the south pacific and it wouldn't necessarily have a big effect on global aridity.

More dramatically: you can make a less arid world by distributing your land and sea more efficiently, in smaller chunks. An "ocean" world covered in billions of tiny islands may have more land in total than ours, with lower aridity - because no land is more than a couple of miles from the sea. And you could probably even increase the landmass, if you joined the islands up into narrow, long peninsulas. And even if you made most of the world land, but cratered the land with mini-seas and giant lakes, nowhere would be too far from water. Now, the landier you made such a world the drier it would get: nowhere would be close to a big body of water, so there's be no equivalent of the sodden, dripping air that flows across our atlantic and pacific to drench places like southern china. Tropical rainforests would be highly restricted if they existed at all - most places would be semi-arid. They'd be like desert islands or the shores of large oases. But they could probably be survivable.


And then there's the second option: get a bigger sponge. If the air can store more water, it can move the water further from land. How could tha air store more water? Well, you could mess around with the composition of the air somehow. Or just reduce the average pressure - though that might have severe consequences in other regards! Or, easiest of all, increase the temperature: hot air can hold more water. There's a limit to this, of course, but in general if you have a hotter world it will be wetter. That's why the Sahara used to be covered in grass, and why our grasslands used to be covered in lush forests, when the world was hotter. So if you make a wet, hothouse world, you can then increase the relative land mass and bring the average humidity back down to our levels. It may make some areas uninhabitably wet and hot, but it will probably open up much larger areas as survivably humid and cut down drastically on the giant deserts.





That's if we want increased precipitation. But we could also lower evaporation. How would we go about this? Higher-pressure air would be one option. Lower wind-speeds. Or more simply, lower temperatures. Look how much land is covered by the taiga! You don't need much rain if you can reduce the amount of water being lost from the soil (and the permafrost is plenty wet!). If you did also break the land up more efficiently, you could keep a trickle of rain coming, and then low evaporation could keep the soil damp.


-------------------

So, we can construct a typology of low-ocean worlds:

A: desertworlds. These have huge continents and small but substantial seas. Most of the land is arid and effectively uninhabitable. However, there may be perfectly livable areas too - even some extremely wet ones, depending on geography. Damp areas will occur on the coasts, and in certain upland areas (particularly if the rest of the land is flat).

B: lakeworlds. These are all land, punctuated by huge lakes (small inland seas). There are probably no really wet areas at all, but the windward shores of the lakes may be moist enough to live, and put together there may be much more liveable land than in the desertworld scenario. High wind speeds would help (more evaporation off the lakes).

C: oasisworlds. These are land puncutated by vast numbers of small lakes. So little water is taken from these lakes by the air that only the immediate shoreline is moist - but there are so many lakes that that can add up to a lot of shoreline. Unlike the lakeworld scenario, basically any journey here will involve crossing desert. [one problem here might be the difficulty of evolution... same for lakeworlds]

D: hothouseworlds. These have whatever distribution of land, but significantly higher temperatures. This allows moisture to penetrate much further into the interior of continents, even with less ocean in total. However, some tropical areas may be uninhabitable through heat.

E: taigaworlds. These are cold, low-evaporation planets. Nowhere has much rain at all (although some limited coastal areas may get plenty), but a lot of the land is vaguely damp. Expect bogs and, in colder areas, permafrost (such a world will presumably have big icecaps too). Presumably glaciers higher up - settlement may seek out meltwater rivers, as the rest of the water will often be brackish - rivers will probably be very important, since low evaporation means water has to drain away through big river (many of earth's biggest rivers are in the taiga). Snow most of the year, and a lot of mist and fog. [Obviously, the world won't literally all be taiga; there'll be steppe too, and probably some desert]

F: iceworlds. Obviously, you can have plenty of water if it's all frozen! That does cause its own problems, needless to say. But if most of your planet's land is covered in ice, you could have substantial areas with liveable moisture levels where there is no ice. For instance, if most of your land has a high altitude and is below freezing and covered in glaciers, you could have countless deep canyons in which there may be almost no precipitation, but in which the meltwater from the glaciers (and the freezing fog that rolls down off the hills) provides enough water at warmer altitudes to allow agriculture.
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Re: higher pergentage of land?

Post by k1234567890y » Sat 28 Apr 2018, 16:16

wow thanks (:

you seem to be very knowledgable in this kind of things, Salmoneus
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Re: higher pergentage of land?

Post by DesEsseintes » Sat 28 Apr 2018, 17:41

My conworld is a type B lakeworld. I know this now thanks to Sal. [:D]
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Re: higher pergentage of land?

Post by k1234567890y » Sat 28 Apr 2018, 17:44

DesEsseintes wrote:
Sat 28 Apr 2018, 17:41
My conworld is a type B lakeworld. I know this now thanks to Sal. [:D]
nice (: so you have come up with a lakeworld independently? (:
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Re: higher pergentage of land?

Post by Salmoneus » Sat 28 Apr 2018, 20:01

k1234567890y wrote:
Sat 28 Apr 2018, 16:16
wow thanks (:

you seem to be very knowledgable in this kind of things, Salmoneus

Not really - that's all just common sense. And may of course be wrong!

[I'll also stress: that typology is just off the top of my head, not something standardised or anything]
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Re: higher pergentage of land?

Post by k1234567890y » Sat 28 Apr 2018, 20:54

ok nice lol but still thank you Salmoneus (:
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