Subterranean environments on Golarion

[Elric200]

Can someone explain why the subsurface lands on Golarion so much warmer than on earth. I just watched a youtube video on a caving expedition to the deepest known cave on earth in the Caucus mountains about 7600 feet deep and after about 3000 feet the cavers had to wear special gear because the temperatures were just above freezing and very wet and prone to flooding. Also do the underdark races use some form of elevators to traverse the depths if not why don't they get racial bonuses to their climb checks.

[keftiu]

The Darklands are a magical cave network influenced heavily by planar gateways and the fact that Golarion’s core is the prison of Rovagug. It’s not just a mundane “underground” ecosystem like Earth.

[James Jacobs]

The primary reason that the Darklands exist in the way they do and aren't more realistic like what you'd see on Earth is, as Keftiu mentioned: Magic.

But not so much the fact that Rovagug is imprisoned within the planet, since his actual prison plane is separate from the Material Plane (and thus physically separate from the planet's core).

It's more the result of...

Spoiler:

... the extensive magical terraforming done down there by the Vault Builders in the ancient past; they created the Vaults of Orv in a way that created sort of "terrariums" deep down below that allowed a wide range of enviornments to exist, using their magic and mastery of elemental earth to make it happen, and those Vaults of Orv seep that magic upward to make Sekamina and Nar Voth habitable as well.

Without this, it wouldn't be extreme cold that would trouble travelers into the Darklands, but a combination of air pressure and extreme heat.

As for how the people of the Darklands get around... all sorts of ways. Some climb. Some fly. And there's enough winding tunnels that the main way they get around is just to walk up and down those long underground passageways.

The secondary reason that the Darklands exist in the way they do is to give us and you a fun, strange, frightening, alien environment to place adventures in.