The matter-antimatter annihilation near the boundary would generate enough energy to blow the antimatter shell into deep space (where it would cause some seriou

The matter-antimatter annihilation near the boundary would generate enough energy to blow the antimatter shell into deep space (where it would cause some serious problems for the rest of the Solar System). The released energy would likely (I haven't done the math) be enough to vaporize the Earth, which would meet the original requirements, but I don't think it would annihilate a large percentage of the Earth's mass.