Earth Sci Module 4

Fossil fuels are natural sources of fuel that formed through geological processes. They have been used as sources of heat and medicine by early civilizations. They remain as primary sources of energy until today.

Fossil fuels are deposits of organisms (biomass) that are primarily used for energy generation. They are formed millions of years ago. They form when the remains of organisms are buried under layers of sediments immediately after they perished.

Fossil fuels were able to form because the remains of the different organisms experienced only little to partial decomposition. Fully decomposed remains turn to humus instead.

Coal is a rock-like material made from plant matter that lived in swampy areas and is widely used as a fuel.

Crude oil is unrefined petroleum extracted from the underground reservoirs. It can be treated to form other products such as gasoline, plastics, and tar.

Natural gas is a naturally occurring hydrocarbon gas made up of methane and other alkanes such as butane and propane. Natural gas can be used as fuel for cooking and generating electricity

Types and Formation of Coal

• Peat is an accumulation of plant organic materials that only partially decomposed due to exposure to water and carbon dioxide. It is recognizable due to the evidence of plant remains and water. Peat is quite unconventional to use because it needs to be dried out and it produces large amounts of smoke.

• Lignite is formed when increased pressure from sediments transforms peat. It still has traces of plant remains. It is abundant but used only when more efficient fuels are unavailable.

• Bituminous forms when even more pressure is applied to lignite. No trace of plant materials can be observed in this stage. It is the most abundant form of coal and a major source of heat energy.

• Anthracite is the last stage of coal formation. It has the hardest consistency among the stages of coal. This form resulted from extreme pressure and high temperature on the layers of sediments. Anthracite burns with a short flame and only produces a little smoke.

Crude Oil Formation

First Stage

• Marine plants and animals gather energy from the sun and their food to increase the organic materials in their bodies.

• When they perish, their bodies sink under the ocean.

Second Stage

• The remains of the marine organisms are buried under sediments as time passes.

Third Stage

• More sediments bury the remains of marine plants and animals.

• These sediments turn into sedimentary rock after millions of years.

Fourth Stage

• The heat and pressure from the sedimentary rock slowly turn the plant and animal matter into crude oil.

• Some of the crude oil migrate in porous rocks while others remain trapped in impermeable rock reservoirs.

The most widely used method to process crude oil is fractional distillation.

Gas, gasoline, kerosene, diesel oil, fuel oil, tar, and paraffin wax are all produced when crude oil undergoes fractional distillation.

Processing of crude oil also yields byproducts such as petroleum jelly, fertilizers, vitamin capsules, and others. Crude oil is the most commonly used source of energy in the world.

Natural Gas Formation

Stage 1

• Microscopic plants and animals from the ocean die and sink to the bottom of the ocean. Sediments, plants, and bacteria form layers above these organisms.

Stage 2

• Heat and pressure increase as the remains of these organisms are buried deeper by sediments. A biomass made from plant materials and exposed to greater heat produces natural gas.

Stage 3

• The natural gas migrates through the pores in the rocks. Some escape to the Earth’s surface while others are caught in impermeable rocks and clays and become trapped deposits of natural gas.