Fossil Fuel Background Information
Viewed from space, the most dominant color on the surface of the Earth is blue due to the fact that nearly seventy five percent of the surface of the Earth is water. It is one of the special characteristics of our planet that allows for life to exist and the primary concern for astronauts and scientists who aspire to visit other planets. Water in its purest form is a clear, tasteless liquid; however in daily observation and use, it can be classified using the characteristics of clarity, color, salinity (saltiness), and taste.
The Earth is a round ball of rock. The interior of the Earth may be molten liquid magma, and the surface of the Earth may be covered with plants, water, ice, buildings or soil, but the surface is rock. Only the outer layer of the Earth, the crust, has rock in it. Rock is a very important resource for human welfare. In its natural state it was probably the material for the first home, the first tool, and the first weapon. Rock is still very important today in the construction of homes, large buildings, roads, sidewalks, and parking lots. Even many very small objects in our homes come from rocks. Talcum powder comes from talc, a sedimentary rock. Most of the metal we use today, from aluminum foil in the kitchen to massive steel towers, is a refined form of rock we have removed from the Earth.
A rock consists of one or more minerals. The type and proportion of minerals in a rock determines its texture, color, and density. Rocks can be classified according to physical characteristics such as size, shape, texture, color, density, mass (weight) and even taste. Some rocks are magnetic, and some rocks will actually float in water due to their low density. Due to their different characteristics, rocks are used for different purposes. Many years ago obsidian, very glass-like and easily broken into sharp edges, was used for cutting, while granite, because it has a rough texture and is hard to break, was used to make grinding and hammering tools. Classifying rocks may be done in the classroom using the students’ senses of touch, sight, and even taste (as with halite), along with labs tools such as scales, rulers, and microscopes.
In the natural world the surface of the Earth is constantly changing, and rock is constantly being broken down into smaller and smaller bits of rock. This process of weathering, or the breaking down of rocks, is due to the effects of wind, water, and ice. Wind blows small particles of rock and sand against large rocks, and it has the effect of sandpaper slowly grinding away the surface of the rock. Water, especially water already carrying small particles of rock, flows over large rocks and will slowly wear away the surface. When water seeps into rocks and freezes to become ice, it expands in size and breaks down large rocks.
The life cycle of living organisms results in the decaying of plants and animals into the ground. This decayed material, called organic matter, mixes with the small particles of rock to create soil. For plants to grow well in soil there must be a proper balance of organic matter, water, and rocks of the right size. For example, a sandy desert soil may have rock particles that are the right size to promote healthy plant growth, but without water and organic matter to mix with those particles, plants cannot grow well. We can determine the physical characteristics of soil by observing the particle size of the rock, the organic matter content, and how well the soil retains water. By observing a soil sample's physical characteristics, we can predict the best use for it and determine which soils have the best ability to support the growth of plants.
Loose particles, such as sand, pebbles, and shells, are known as sediments. When sediments are laid on top of other sediments, the ones at the bottom become compressed and turn into sedimentary rocks. Sedimentary rocks form in two ways: (1) through compaction where the grains are squeezed together by the weight of the layers of sediment above them, and (2) through cementation where the minerals in water fall out of suspension around the particles and act as glue, sticking the sediments together. Due to the fact that sedimentary rock generally has a physical characteristic of being layered, geologists can drill into layers of sedimentary rock and determine a time line for geologic events in an area.
Two types of ancient sedimentary rock formations are the sources of all the fossil fuels we burn today to generate electricity. First, in ancient swamps, prehistoric plants and trees began to disappear 300 millions of years ago during the Carboniferous period, long before dinosaurs appeared. The plants remains were covered with soil, layer upon layer. A thousand years of heat and pressure slowly turned these compacted, decayed plant layers into peat. However, it takes hundreds of millions of years more for heat and pressure deep withing the Earth to turn peat into coal.
A second type of sedimentary rock formation occured at the bottom of ancient oceans and seas when tiny marine animals called "diatoms" died and sank. They, too, were covered with layers of sand. Millions of year of heat and pressure turned their remains to oil and natural gas trapped in layers of sedimentary rock. Because plant and animal remains were sources for these fuels, they are called fossil fuels. Nature is not replenishing this supply of fuel, so coal, oil, and natural gas are considered nonrenewable resources. The pollution produced from burning fossil fuels has lead to an increased interest in alternative energy sources.