Planet Earth is approximately 4,5 billion years old. In the beginning, the Earth was a cold planet, but in time its temperature started to rise. As a result of the rising temperature, the heaviest substances sank deep inside the planet to form its core, and lighter rock remained "floating" on the surface of the planet. As a result of this process, planet Earth gained its layers.

The internal layers of the planet contain energy. This energy causes changes in the Earth's crust. These changes are manifested as different phenomena, such as earthquakes. These phenomena originate from inside the planet, and are therefore called endogenous processes. 

The energy radiated to the surface of the planet Earth from the Sun also modifies the planet's crust. These phenomena include wind and rain. Because these processes originate outside the planet's surface, they are called exogenous processes.