Undertop Steampunk

The dwarves of the Revered Kingdom of Undertop occupy the tallest mountain in Rodinia, and have resided there for untold millennia. In that time, they have carved out huge swathes of space under the mountain. They have tunneled so far down into the ground, they have accessed great volcanic vents full of scalding hot steam coming up from the bowels of the planet. At first, they used the heat to warm the portions of their underground kingdom that required it.
Then, they used the steam to fill saunas for the general public to use.
Then, they used the steam to get wrinkles out of their clothing.
Then, they used the heat to forge weapons.
Most recently, an ambitious team of siege engineers came up with a new use for the limitless supply of steam. They proposed the creation of a unique defense system for their mountain kingdom. They suggested creating a series of horizontal tunnels leading from the interior of the mountain to the exterior, putting a large boulder inside each one, and letting steam build up behind each boulder, until the pressure ejects the boulder out of the tunnel with the speed of a missile.
The administrative elders were impressed with the proposal, especially how it could utilize scrap boulders produced from mining. They ordered the system to be constructed and put into place, to be utilized at a moments' notice. The Strategic Divination Section did not have any intelligence indicating they would be attacked by any known army, monster, group, or entity in the near future, but it never hurt to be prepared to defend one's home.
Even before the system is fully in place and tested, the crack engineering team is already developing plans for a mobile boulder launcher, as well using steam as a form of locomotion.
One creative dwarf has an idea to create a large iron bipedal construct and operate it with steam, perhaps for combat purposes, or perhaps for construction purposes.
It is fascinating to speculate how geothermal energy can influence the development of a society, and even more fascinating to see how a society's cultural mores and standards dictate and shape how said society uses such energy.

Image generated by DeepAI. (2024). AI Image Generator. DeepAI. https://deepai.org/machine-learning-model/text2img