Final answer:
The rock layer called a source rock is rich in organic matter and subjected to heat and pressure to form oil and natural gas. These fossil fuels are the result of organic matter being buried deep underground and transformed over millions of years. Critical factors include the depth of burial, temperature, and pressure conditions.
Step-by-step explanation:
The rock layer that must be rich in organic matter and is subjected to heat and pressure over time during the formation of oil and natural gas is known as a source rock. This sedimentary rock contains enough organic matter that, when subjected to the geological processes of being buried deep underground, it is exposed to heat and high pressure conditions. Over millions of years, these conditions convert the organic materials into fossil fuels, namely oil and natural gas.
For the creation of these fossil fuels, the organic matter must be buried under soil, sand, or ocean or river sediments. As it is compressed and heated over time, the organic matter transforms, first into a thick liquid oil, and then into natural gas if subjected to even deeper and hotter environments. The organic matter should be buried at least 2 km deep to crack large organic molecules and not more than 4 km deep to avoid overcracking into natural gas.
Fossil fuels like petroleum and natural gas are the product of a long process that began with the accumulation of dead microscopic plants and animals, primarily in the oceans. These remains were then buried under layers of sediment, which over time turned into rock. The energy content found in these fuels is a direct result of the chemical transformation of past sunlight into biomass, and then the 'anaerobic cooking' at high pressures and temperatures that took place over millions of years.