Which phenomenon occurs during a nuclear explosion?

The phenomenon that occurs during a nuclear explosion, which is correctly identified, is the extreme release of temperature and pressure. During detonation, a nuclear reaction generates an enormous amount of energy almost instantaneously. This energy is released in the form of a shockwave accompanied by an intense burst of heat that reaches temperatures in the millions of degrees Celsius. The rapid expansion of gases and materials from the explosion creates a high-pressure wave that can cause extensive destruction in the vicinity.

While smoke cloud formation, nuclear fallout management, and evacuation warnings issued may be associated with the aftermath or consequences of a nuclear explosion, they do not directly describe what happens during the explosion itself. Instead, the extreme temperature and pressure release is a fundamental characteristic of the explosion process, leading to the immediate and catastrophic effects on the surrounding environment.