Petroleum ("oil") and natural gas are hydrocarbons that formed over millions of years under heat and pressure deep in the Earth. Petroleum and natural gas are the largest sources of energy in the United States.
Petroleum ("oil") and natural gas form from tiny plants and algae that settled in seas or lakes millions of years ago. This organic material reacts under heat and pressure to form oil and/or gas. Petroleum products include gasoline, heating oil, propane, and kerosene. Not to be confused with gasoline, natural gas is mostly methane — a clear, odorless gas. When burned, oil and gas release abundant energy as well as carbon dioxide and water. Read more