Nuclear weapons are explosive devices that unleash a tremendous degree of destruction through nuclear reactions, which release a great deal of energy in the form of heat. There are several nuclear weapons effects that range beyond the massive heat and energy release, for which they're best known. The effects can be tangible, physical results, such as radiation and cratering. Nuclear weapons effects can and do also extend into the realm of politics; international laws exist that forbid the use of such weapons, for instance. Nuclear weapons have such disastrous effects on people and the environment that they are considered, at an international level, weapons of mass destruction.
Nuclear weapons effects tend to be deadly to human, animal, and plant life that exists anywhere near the blast. Based on the size of the weapon used, organisms can be affected for miles around the site of the weapon's detonation. Near the blast site, the heat is so intense that most living things are immediately vaporized. Immediately after the initial blast, the extreme heat causes a high-pressure wave of hot air to move outward at a high velocity, causing tremendous destruction and, again, destroying most living things.
The heat and high pressure also affect structures and environmental features of an area. The blast radius of a nuclear weapon depends on the size of the weapon, but it is usually quite large. A single nuclear weapon could easily level an entire city. All human-built structures, trees, and everything else could be reduced to little more than a crater.
The emission of large amounts of radiation is also among the notable nuclear weapons effects. There is, upon detonation, an initial burst of radiation that people can receive in lethal doses if they are close enough. In most cases, however, the people who are close enough to be affected by the initial burst are killed by the heat and force of pressure. After the blast, however, nuclear weapons leave a significant amount of residual radiation that can damage the environment and harm people living nearby. Most notably, high levels of radiation exposure can cause cancer in humans and in other organisms.
The existence of nuclear politics is one of the major nuclear weapons effects. The control of nuclear weapons gives a nation a great deal of military and political power; some nations that control nuclear weapons could completely destroy centers of industry or populations in other nations. Despite many international laws attempting to control nuclear weapons, the control of such weapons remains an issue of great political significance.