Final answer:
Natural gas is typically found in reservoir rocks such as sandstone or limestone and coal deposits within the Earth's crust. These fossil fuels are formed from the decomposition and transformation of organic materials under high pressure and temperature conditions over time. The availability of natural gas in these formations is shaped by geological history and plate tectonics.
Step-by-step explanation:
Natural gas can be found in several types of geological formations within the Earth's crust. Two common places where natural gas is found include reservoir rocks and coal deposits. Reservoir rocks, which are often made of sandstone or limestone, can hold natural gas along with petroleum, and these fossil fuels are sometimes extracted together. Coal deposits can also contain natural gas, particularly in the form of methane, where the organic material from ancient plants has undergone chemical transformations over millions of years.
In both cases, the presence of natural gas is the result of organic materials being subjected to high pressure and temperatures over geological time scales. For reservoir rocks, the process is thermogenic, meaning that the organic matter has been exposed to high temperatures and pressures deep underground, leading to chemical reactions that generate the gas. In contrast, biogenic gas found near the surface is produced through the anaerobic decay of organic matter by bacteria. Techniques like hydraulic fracturing, or fracking, may be employed to extract this gas from rocks with low permeability.
The occurrence of these deposits is largely influenced by the geological history of the area, including the types of plate boundaries or stresses that would impact rock formations over time, making certain regions more likely to contain natural gas.