What is an example of a non-renewable energy source?

Petroleum is classified as a non-renewable energy source because it is formed from the remains of ancient marine organisms that have been subjected to heat and pressure over millions of years. The extraction and consumption of petroleum deplete this resource at a rate that exceeds its natural replenishment. This means that once petroleum reserves are exhausted, they cannot be readily replaced.

In contrast, renewable energy sources like wind and solar are continually replenished by natural processes, and geothermal energy is derived from the Earth's internal heat, which is also sustainable over time. The distinction lies in the finite nature of petroleum compared to the sustainable characteristics of the other energy sources listed.