Oil was formed from the remains of animals and plants that lived millions of years ago in a water environment, before the dinosaurs. Over the years, the remains were covered by layers of mud. Heat and pressure from these layers helped the remains turn into what we today call crude oil . The word "petroleum" means "rock oil" or "oil from the earth."
Crude oil is a smelly, yellow-to-black liquid and is usually found in underground areas called reservoirs. Scientists and engineers explore a chosen area by studying rock samples from the earth. Measurements are taken, and, if the site seems promising, drilling begins. Above the hole, a structure called a 'derrick' is built to house the tools and pipes going into the well. When finished, the drilled well will bring a steady flow of oil to the surface.
The world's top five crude oil-producing countries are:
Oil is usually burned to produce energy.
ADVANTAGES
Oil is used to help us do many things: we use them to fuel our airplanes, cars, and trucks, to heat our homes, and to make products like medicines and plastics. It makes products that make our lives easier, and we know how to use it to make energy. Crude oil (called "petroleum") is easier to get out of the ground than coal, as it can flow along pipes. This also makes it cheaper and easier to transport around the world to where it is needed.
DISADVANTAGES
Basically, the main drawback of fossil fuels is pollution. Using petroleum products gives off pollutants that help to form air pollution. Burning any fossil fuel produces carbon dioxide, which contributes to the "greenhouse effect", warming the Earth.
Scientists and geologists are also very concerned that supplies of oil are going to run out soon. Most of the oil that is easy to get to, is already out of the ground, and what is left is harder and more expensive to get to. As the world gets shorter and shorter of oil, countries may go to war to fight for access to oil. Many people think this is why the United States has gone to war in the Middle East.
Another problem with oil, is that if it leaks or is spilled, it gets into rivers or the sea, and it harms wildlife. Even leaks of oil on your drive eventually get washed into gutters, waterways, and eventually get to the sea.