I need some help figuring out geological features

[084thebull]

So I have an idea for a campaign seting/country for a (as of now) still none existing D&D campaign i'd like to run.
The basic premise of the idea is that a sizable sea got cut of from the ocean and thus evaporated leaving behind a salt flat desert situated well below the sea level and "mountains" with what used to be islands on top (this actually happened to the Mediterranean sea which is where my inspiration came from).
Today i drew up a sketch of the map with the important features, the thing is i'm having a bit of a hard time figuring out the geology of it all.
2016-04-25 18.19.16.jpg
now for the legend:
light blue= fresh water - dark blue= salt water - thick lines indicate cliffs (think Mount Roraima) - and the strip of ogre yellow down there is a massive sand slope leading to the neighboring (sand) desert (i refer to it as "the beach") - mountains are triangles and green is plants but you got that far already i'd bet.

I have so many questions:
what kind of climate would this area be now that an entire sea is no longer there?
how do mountain ranges behave?
how much would the cliffs slope if at all ?
what happens to coral reefs if the sea they're in evaporates ?
How does one properly scale a map like this (the whole basin is pretty damn huge think maybe 2/3 of the Mediterranean sea)

this would probably also be the time to mention that while i have Photoshop,corel painter and a Wacom i am not even remotely proficient with any of them, i'm far more comfortable with "traditional" Mediums (media ??).

In my mind this entire country is "walled in" by massive 400/500 meter high cliffs except for at the bottom where "the beatch" and the top right corner where a mountain range comes down into the basin but how plausible is that ?
pfffff so many questions i can feel myself getting lost in it all.

I eagerly await your sagely advice o wise ones.

[jbgibson]

One theorized result of such a deep basin (ancient Mediterranean for instance) has it horribly dry, dry, dry - so hot in general that most any precipitation evaporates before reaching ground. Rivers from adjacent high (normal) elevations would waterfall / cascade down the rim and maybe survive to be some standing water at the bottom. The evaporate-as-it-rains would maybe generate constant haze above, so denizens below might not know of stars.

High air pressure could even be a strong effect - just how deep are you considering this dry basin?

See the Gandalara Cycle for a good fictional treatment.

[084thebull]

talking about mountains I've reconfigured them since posting this thread,
here's what i have now:
Attachment 83001

[Azélor]

what kind of climate would this area be now that an entire sea is no longer there?

Logically, if it's a desert it's because it's dry, so there is little rain falling. If the area receives rain, it receive less than the total evaporation, generally over the course of a full year.
Temperature wise, the diurnal temperature gradient is larger. The presence of water tend to limit extreme temperatures. Lack of water means cool nights and very hot afternoons. The seasonal difference of temperature will be larger only if it's in the higher latitudes. The continentality of the Sahara is small regarding season temperatures, and would not be much greater in the Mediteranea. But it is much larger is Siberia for example (not a desert but a continental climate).
The rim of the old sea also become much drier since they lose their main source of moisture.

how do mountain ranges behave?

You mean their impact of the climate or how the are formed? about plate tectonic, there are 3 types of boudaries: https://en.wikipedia.org/wiki/Plate_tectonics

how much would the cliffs slope if at all ?

Not sure what you mean. As you mentioned Mount Roraima is really steep (90 degrees or almost). Can't get steeper than that.

what happens to coral reefs if the sea they're in evaporates ?

They die. Coral are animals, so after their death I guess they will decompose overtime. I'm not sure if they will fossilize or if they will disappear carried by the winds.

How does one properly scale a map like this

That depends on you. A map is a representation of the world. If you want you could have trees and mountains at the same scale but it would be practical. You have to find a scale your comfortable with depending on how much detailed you want the map to be. Putting more stuff or going for a more realistic approach is more immersive when you look at the map, but it takes way more time.

[084thebull]

The seasonal difference of temperature will be larger only if it's in the higher latitudes. The continentality of the Sahara is small regarding season temperatures, and would not be much greater in the Mediteranea. But it is much larger is Siberia for example (not a desert but a continental climate).
The rim of the old sea also become much drier since they lose their main source of moisture.

Thanks that's some really useful info on the climate!
I was mostly hoping to have a more water rich and green country on the other side of the mountains but if i situate this more or less in the equivalent of the Mediterranean that should be doable by the sounds of this using the mountains as a barrier that keeps the rain mostly on that side.

As for the mountains i was wondering both but i think I've mostly figured out how it formed but i am indeed still curious on their effect on the climate for instance how much of a climate difference could there be between the one side of a big mountain range and the other side ?

[Azélor]

Thanks that's some really useful info on the climate!
I was mostly hoping to have a more water rich and green country on the other side of the mountains but if i situate this more or less in the equivalent of the Mediterranean that should be doable by the sounds of this using the mountains as a barrier that keeps the rain mostly on that side.

As for the mountains i was wondering both but i think I've mostly figured out how it formed but i am indeed still curious on their effect on the climate for instance how much of a climate difference could there be between the one side of a big mountain range and the other side ?

That would depend on the direction of the winds,. Dominant winds TEND to blow from east to west at the equator and in high latitudes but from west to east in mid latitudes. I said tend because some factors including large landmasses will affect the directions of the winds. Such as the East Asian monsoon blowing from east to west in mid latitudes, in summer.

But of course, if you don't like this you can inverse the rotation of the planet. This will the change direction of the winds.

The difference between the two sides of the range can be very large. If you look at the Andes, you will see a sharp contrast between the Atlantic side and the Pacific side.

https://www.google.ca/maps/place/P%C...9e011279210648

The eastern slopes are mostly made of rainforest and the western side is one of the driest place on the planet. Antofagasta really receives about 1mm of rain per year on average, and that's more like the ambient humidity because real rain happens once every few decades or something.

Another thing is how montaneous areas can be rainier than their surroundings. It can be seen in several places including South west USA, Iran, and Central Asia
https://www.google.ca/maps/place/P%C...9e011279210648

It is kinda hard to see here but a lot of these mountains in Iran receive about as much water as many southern European cities like Rome, wile the valleys are much drier. I would also need to add the since mountains are higher, they have a lower temperate on the ground and therefore there is less evaporation. It's harder to have a desert in altitude but not impossible if dry enough.
https://www.google.ca/maps/place/P%C3%A9rou/@32.943533,49.2149545,973936m/data=!3m1!1e3!4m2!3m1!1s0x9105c850c05914f5:0xf29e0 11279210648

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By the way, your last attachments are not working. You might have been disconnected while uploading them.

[084thebull]

oooh that sounds great!
i don't quite know yet but if i were to stick with the Mediterranean the average depth would be about 1.5 Km (or slightly under a mile) with the deepest point being over 5 KM i was thinking in the form of a massive canyon still maybe 2/3 full with left over sea water (and the gods only know what kinds of sea creatures managed to survive down there).
but it would probably steadily slope up towards the edges until hitting the cliffs.
Gandalara looks really cool by the way, i personally am taking some of my inspiration from frank Herbert's Dune saga