Figure 5.3: Refineries like this one separate crude oil into many useful fuels and other
chemicals. ( 1 )
main oil producing regions are the Gulf of Mexico, Texas, Alaska, and California. Most of
California’s oil fields are in the southern San Joaquin Valley. Compression from when the
region was a convergent plate boundary produced a set of anticlines that are parallel to the
San Andreas Fault. Oil collects in permeable sediments that are capped by an impermeable
cap rock. Oil is also pumped on and off the southern California coast.
Oil as it comes out of the ground is called crude oil. Crude oil is a mixture of many different
hydrocarbons. Oil refining is used to separate the compounds in this mixture from one
another (Figure 5.3). We can separate crude oil into several useful fuels because each
hydrocarbon compound in crude oil boils at a different temperature. An oil refinery heats
the crude oil enough to boil the mixture of compounds. Special equipment in the refinery
separates these compounds from one another as they boil.