<P> Gamma rays from the nuclear processes preceding the true explosion may be partially responsible for the following fireball, as they may superheat nearby air and / or other material . The vast majority of the energy that goes on to form the fireball is in the soft X-ray region of the electromagnetic spectrum, with these X-rays being produced by the inelastic collisions of the high speed fission and fusion products . It is these reaction products and not the gamma rays which contain most of the energy of the nuclear reactions in the form of kinetic energy . This kinetic energy of the fission and fusion fragments is converted into internal and then radiation energy by approximately following the process of blackbody radiation emitting in the soft X-ray region . As a result of numerous inelastic collisions, part of the kinetic energy of the fission fragments is converted into internal and radiation energy . Some of the electrons are removed entirely from the atoms, thus causing ionization, others are raised to higher energy (or excited) states while still remaining attached to the nuclei . Within an extremely short time, perhaps a hundredth of a microsecond or so, the weapon residues consist essentially of completely and partially stripped (ionized) atoms, many of the latter being in excited states, together with the corresponding free electrons . The system then immediately emits electromagnetic (thermal) radiation, the nature of which is determined by the temperature . Since this is of the order of 10 degrees, most of the energy emitted within a microsecond or so is in the soft X-ray region . To understand this one must remember that temperature depends on the average internal energy / heat of the particles in a certain volume, and internal energy or heat is due to kinetic energy . </P> <P> For an explosion in the atmosphere, the fireball quickly expands to maximum size, and then begins to cool as it rises like a balloon through buoyancy in the surrounding air . As it does so it takes on the flow pattern of a vortex ring with incandescent material in the vortex core as seen in certain photographs . This effect is known as a mushroom cloud . </P> <P> Sand will fuse into glass if it is close enough to the nuclear fireball to be drawn into it, and is thus heated to the necessary temperatures to do so; this is known as trinitite . </P> <P> At the explosion of nuclear bombs lightning discharges sometimes occur . </P>

How much land does a nuclear bomb cover