Petroleum or oil is a thick, yellow to black liquid found in rock layers. It is made up of organic material, formed millions of years ago from dead plants and animals. Deep in the ground pressure and heat transformed them into oil. Crude oil is oil in its natural state. Oil has been used in one form or another over thousands of it has become really important to ou years but econo in centuries. It has been the most it source of energy since the end of World War ll The first oil well was created in the middle of the 19th century in Pennsylvania. By 1870 oil production had spread to other American states. During the latter part of the 19th century oil was also produced in Canada and in European countries. The of the early 20th century led to a higher demand of oil. It played an important ro automobile boom as the main fuel for tanks and planes in the two world wars. By 1950 the United States had become the world's largest oil producer. In the second part of the 20th century Saudi Arabia and Russia produced even more than the USA. erea hy oil products. oil consumption mi ul inn Most of the world's oil is needed in the western world fie fini consumer. It uses up about a nnh of the daily oil frode fion, imwn, other major consumers of oil. Environmental effects of oil production Producing and consuming oil and oil products affects our environment in many ways, It is a major cause of global warming because burning fuel releases carbon dioxide, thus causing the greenhouse effect. Oil drilling is often damaging to the environment because chemicals are used to separate oil from water. In the past decades there have been a series of tanker accidents that have polluted the world's oceans and seas. The biggest disaster was the sinking of the Exxon Valdez off the coast of Alaska in 1989. in 2010 an oil spill in the Gulf of Mexico spread to coastal areas in the USA and Mexico and polluted thousands of square kilometers of water.