Non-renewable resources are those natural resources which are finite in quantity and cannot be replenished once depleted. Petroleum is an example of non-renewable resources because it is formed over millions of years from the remains of dead plants and animals buried deep under the earth's surface. Once extracted and used, it cannot be replaced or renewed.

Reasons for Petroleum being a Non-renewable Resource:
1. Finite Quantity: Petroleum is a finite resource, which means that there is only a limited amount of it available on the earth's surface. Once the reserves are depleted, there will be no more petroleum left to extract.

2. Extraction Cost: The cost of extracting petroleum is very high, and it requires sophisticated technology and infrastructure. As the easy-to-extract reserves are depleted, the extraction cost will continue to rise, making it economically unviable to extract.

3. Environmental Impact: The extraction, transportation, and use of petroleum have a significant environmental impact. It is a major contributor to air and water pollution and greenhouse gas emissions, which contribute to climate change.

4. Dependency: Most of the world's economies are heavily dependent on petroleum for their energy needs. As the reserves are depleted, the world will face an energy crisis, which will have a significant impact on the global economy.

Conclusion:
Petroleum is a non-renewable resource that is essential for the world's economy. However, it is a finite resource that is being depleted at an alarming rate. There is a need for the world to shift towards renewable sources of energy to reduce dependence on petroleum and mitigate the environmental impact of its use.