The reason why the black hole would evaporate if someone were to make one is hawking radiation. This is due to virtual particles appearing right on the black hole's event horizon. When they appear, they appear as pairs, with one particle falling into the black hole, and the other escaping. The particle that escapes takes some of the black hole's mass in the process. The smaller the black hole, the faster it evaporates through this process. The end result of this is energetic radiation.