Kathleen Fisher, age 12, of Youngstoian, Ohio, for her question:

Why is there so much helium in Texas?

The earth plays a game of hide and seek with her treasurers. She hid a deposit of precious gold for us to find in Northern California. Most of her diamond hordes are concealed in the rocky remains of old volcanos in South Africa. Beds of coal are buried where ancient forests once grew in soggy swamps. Oil deposits are the hidden remains of ancient, shallow seas. Some of them ooze tacky asphalt and a very few are sealed underground with helium and other valuable gases.

The major share of the world's helium seems to be located in Texas, but not all of it. There are large supplies in Kansas and Oklahoma, New Mexico and Saskatchewan. Other countries may or may not have helium in undiscovered gas wells and there may be deposits of helium in the ocean beds. It is one of the ingredients in natural gas, the flammable mixture we pipe to our kitchen stoves. The natural gas wells of Texas, Oklahoma and Kansas may be about two per cent helium. A much richer well in Arizona contains eight per cent helium.

The two most common elements on the earth are oxygen and silicon, while helium is one of the rarest. Out in space, the major elements are hydrogen and helium. Helium accounts for almost a quarter of the material in the monstrous, blazing stars. In the earth's crust it is rarer than precious platinum and only about five atoms of helium may be present among a million gaseous particles of the air. Usable supplies, then, must be extracted from these special natural gas wells.

These concentrations of helium are linked to the formation of natural gas and natural gas is linked to the formation of petroleum. Scientists suspect that this complex blend of chemicals is a residue from small creatures who lived in ancient seas. Most of its molecules are hydrocarbons, usually built only by living cells. Ages ago, upheavals in the earth's crust lifted these seabeds and buried their organic residues under massive layers of rock. In time, heat and pressure changed the oily organic mixture into petroleum.

In the process, light gases rose to the too and usually seeped up through cracks and lost themselves in the air. But in a few cases, the oily mixture was trapped under dense domes of solid rock. The light gases could not escape. They were sealed in underground pockets above the petroleum. The special formations that trapped the natural gas mixtures underground with the petroleum are very rare indeed. Most of them are in North America and most of the world's helium is separated from the natural gas in these wells.

In 1903, helium was identified in a Kansas well. Texas wells began yielding the rare gas in 1929. It is estimated that five major wells in Texas, Kansas and Oklahoma contain 180 billion cubic feet of helium under their dense domes. The United States mines about two million cubic feet a year    and half of this is stored for the future.