Star Blaster energy core explosion.

Beneath the Tortoise, the ground shifted, collapsing downward. The bomb I had created had gone off, silently vaporizing the earth beneath us. And now the ruins of the Cathedral were collapsing into a massive sinkhole.

Fallout Equestria Chapter 43:
https://www.fimfiction.net/story/119190/45/fallout-equestria/chapter-forty-three-the-kingdom-of-the-blind