Answer: 1. geological processes.
Geological processes are those processes that occur deeper layers of earth with respect to time. These processes involves various chemical and physical changes occurring beneath the earth. The formation of fossil fuel like petroleum takes millions of years for accomplishments. These fuels are formed when dead and decaying plant and animal matter remain inside the earth for millions of years. The degree of these geological processes vary from region to region. Therefore, geological processes is a possible reason for the large variation in petroleum reserves across the region.
