Oil Shale
is a fine-grained, dark brown or black rock from which oil can be extracted.
The oil
content however is low. When crushed and refined
most oil shales yield only about 5-10 gallons per
ton of rock. Oil shale is not really important
as of yet but it may become important as the world supply of petroleum starts to diminish. The source of
oil is a substance called kerogen, formed from decayed plants. This is trapped in the oil shale.
| Oil spills cause a lot of pollution and often many animals and plants die as a result. The Exxon Valdez oil tanker released 35.000 tonnes of toxic oil off the coast of Alaska. Although attempts were made to clean up the oil, thousands of seabirds and many other animals were killed by this environmental disaster. Crossword Puzzle |