The reason that nuclear weapons are so feared, is because they have a range of highly destructive effects. As well as the initial blast and resulting firestorm, the effects on the land and environment can be something that lasts for years if not decades.
The initial damage is caused by the blast. The temperature at the centre of the blast becomes hotter than the sun when the bomb is detonated. This means that everything in the immediate vicinity is vapourised straight away.
As well as this, a huge shockwave promptly follows the initial blast of light and heat. This topples buildings and causes more destruction, especially in built up areas such as city centres. Due to the high temperatures, fires then break out in the area.
After both of these two events have occurred, comes the part of the bomb that causes long term effects -the radiation. Fallout is the resulting radiation that lingers long after a nuclear detonation, and this can pollute the land and poison living things in a large area around ground zero – the area where the bomb was dropped. It would take a lot of decommissioning https://soilfix.co.uk/services/decommissioning-decontamination-demolition to get rid of the resulting radiation from a nuclear weapon.
The amount of fallout can vary – depending on the direction where the wind was blowing at the time as well as whether the weapon was a ground burst or an airburst – a ground burst means that the bomb exploded whilst touching the ground so it would have kicked up and spread a huge amount of radioactive earth at the time of the explosion.