Petroleum, from Medieval Latin petroleum, from Latin petra rock(see petrous) + Latin: oleum oil, is a naturally occurring, yellow-to-black liquid found in geologic formations beneath a planet's surface, which was commonly refined into various types of fuels. It consists of hydrocarbons of various molecular weights and other organic compounds. The name petroleum covers both naturally occurring unprocessed crude oil and petroleum products that are made up of refined crude oil. A fossil fuel, petroleum is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and subjected to intense heat and pressure.
Petroleum was recovered mostly through oil drilling (natural petroleum springs are rare). This came after the studies of structural geology, sedimentary basin analysis, reservoir characterization. It was refined and separated, most easily by distillation, into a large number of consumer products, from gasoline and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals. Petroleum was used in manufacturing a wide variety of materials, and it was estimated that Pre Astro Terra consumed about 90 million barrels each day.
Concern over the depletion of Terra's finite reserves of oil, and the effect this would have on a society dependent on it, was a concept known as peak oil. The use of fossil fuels, such as petroleum, had a negative impact on Terra's biosphere, damaging ecosystems through events such as oil spills and releasing a range of pollutants into the air including ground-level ozone and sulfur dioxide from sulfur impurities in fossil fuels. Burning fossil fuels in particular releases carbon dioxide, a powerful greenhouse gas which was the main cause of man-made global warming.
In modern Union society, technology has almost eliminated the need for petroleum on most non primitive planets. It has been replaced by other, less damaging energy sources, and by nanite / molecular replication of other materials for lubricants and reagents.