I'm writing a story and the general idea is about a city that vanishes from the earth because a wormhole spawned on earth in that exact location. It is moved not to another area in space, but to an entirely different spacetime. The wormhole in question only stayed open for a few seconds before it collapsed. So, in this equation energy to keep it open isn't important. How much energy would it take to open up a wormhole for only a few seconds? The wormhole opens to about 4.2 sq miles before it pops and collapses.