Bill Sweeney, Age G, Of Rockford., Ill., for is question:     

How dad natural gas get in the ground?     

One cubic foot of gas fills a box one foot long, one foot wide and one foot  high. In America, we use 6 trillion feet of natural gas each year. But at this rate, there is still enough natural gas left in the ground to heat our ranges and  warm our homes for another 30 years or more.     Natural gas may be buried 250 feet below our feet. Or it may be buried as deep as two miles below the surface of the ground. But it is always buried under a roof of dense and solid rock, such as heavy sha1e. Under the dense shale there are layers of porous rock, such as sandstone and limestone. The natural gas is trapped in the pores of these spongy rocks. The dense and solid roof of rock stops the trapped gas from escaping into the air.

Petroleum is often sealed in the underground rocks along with the natural gas. The oily petroleum, from which we get gasoline, is trapped in still deeper layers of porous rock. We often find natural gas near or resting in the rocks above a supply of petroleum.     The earth took many millions of years to make these precious supplies of petroleum and natural gas. But scientists cannot say for sure how the job was done. We think we know, but we cannot prove the earth's recipe for making natural gas. The recipe was started long ages ago in many swamps and shallow areas. The ingredients, we think, were miniature floating plants.  These tiny plants teemed in the water, thriving on sunshine and dissolved chemicals. Generations of them died and sank down to rot on the muddy floors. The rotting plant use and the soft mud made an oozy mixture. In time, some of the sea water drained away and some of the swamps became dry. The oozy mud became covered with deeper and deeper layers of dry dust and dirt. Maybe earthquakes or volcanoes added piles of lumpy rock. The mixture of fermenting and decaying plant life was buried deeper and deeper underground

The oily mud was pressed and heated under these new layers of heavy rocks. Through the ages, this heat and. Pressure caused the chemicals in the buried ooze to change. Its heavy, oily chemicals become petroleum. Its lighter  chemicals floated to the top and became natural gas. These changes took ages of time, but the petroleum and the natural gas could not escape because they were sealed under a roof of dense and very solid rock.     Natural gas is a mixture of different gases. Most of it is methane, which is the marsh gas given off by rotting swamps. There may be ethane, propane, butane or other gases in the mixture. Natural gas is purified before it is piped into our homes. Some of the gases are taken out to do useful work in industry. They are used to make dyes and cleaning fluids, inks and perfumes, waxes and drugs and many other everyday products.