system
Given the following post, respond as if you're commenting on Reddit:
human
[Discworld] Does the Disc have a mantle/molten rock?

Does the disc have molten rock near the 'middle' layer, or could you mine all the way through and see the Elephants and the Great A'Tuin?
gpt
The disc is a little thicker in the middle than it is at the edge, where it is about 30 miles thick. If you were to go over the edge, or dig through, then yes, you would eventually come to the bottom of the disc and see the Elephants and Great A'Tuin. 

It's unlikely that there is any molten core, as it would mean the Elephants might have their backs get too toasty.