Fossil fuels are formed from the remains of living organisms over centuries (100 to 500 million years ago) buried deep in the ground.
Until 1970, the United States was largely energy independent, using its own reserves. However, after this period, oil companies in the United States were unable to locate new areas. With rising consumption and failing production, the U.S. turned to imported oil from the Middle East primarily. So did Europe and Japan.
There was an energy crisis in the 1970s when the Organization for Petroleum Exporting Countries (OPEC) formed a cartel and restricted oil supplies for larger prices. Shortages occurred and the U.S. paid a lot more money to get its fuel supply back. Oil prices went up for the average consumer as well. After this experience, the government increased production with oil exploration, building the Alaska pipeline and opening old oil fields, stockpiling oil in an underground reserve (enough for roughly over 1 month of supply at 19 million barrels per day), and setting new standards of fuel efficiency for automobiles.
Buying oil from Arab countries in the Middle East has come with a host of problems including involvement in local wars, fluctuating prices and dealing with insurgents and rebels such as the Taliban in Afghanistan and dictators like Saddam Hussein in Iraq.
How long will oil reserves last? With dwindling reserves and increasing demand worldwide, there is concern that there is not enough oil to last the century. In Canada, there are oil shale reserves that are being exploited today as the cost is competitive with oil prices. Oil shale is a sedimentary material containing bitumen, a tar-like, viscous hydrocarbon that can be melted and refined like crude oil. The Keystone pipeline carries oil shale from Alberta, Canada to Oklahoma and Illinois. The United States also has oil shale reserves in the central part of the country. However, the process is laborious and inefficient - a ton of oil shale yields less than half a barrel of oil.