A system of fractal fibers (a fractal tangle) is formed as a result of evaporation of a weakly ionized atomic vapor from a surface in an external electric field. A fractal tangle has the density of a gas but the behavior of a liquid or solid. The tangle-globule phase transition in this system is similar to the transition in a long polymer fiber with self-intersections. The explosive nature of a fractal tangle is due to its high surface energy, since the system consists of nanometer particles and a significant fraction of the molecules are on the surfaces of the particles. An explosion of a fractal tangle is accompanied by a large number of thermal waves propagating along individual fractal fibers. The result is a large number of hot spots moving inside the system. There is a connection between fractal tangles and ball lightning.