In the book a nuke is used. I needed to nuke a small 3 kilometer wide valley.
The method is a deuterium-tritium capsule collapsed by a lithium ring with magnetism. The amount of fuel could be variable, allowing the nuker to set the size of the detonation, I’m thinking. I’m not sure about this, so I didn’t specify that in my writing.
What I did do was research nuclear bursts, and the areas of effect.