Rita Taylor, age 10, of Sioux City, In., for her questions
What is the earth made of?
The solid earth is made of rocks and metals. Here and there the various rocks are covered with thin layers of soil or sand.. The earth, as we know, is a round ball and its rocks are arranged in layers somewhat like the layers of an onion. The lightest rocks are in the outer crust. Under the crust the layers are heavier and heavier. The core of the earth in the center of the solid ball is heaviest of all and we believe it is made of iron and nickel.
The earth's crust is far from dull for it is made of a great variety of different rocks. There is granite and marble, there is quartz and sandstone. There are a few well known rocks which you may be able to recognize, But there are hundreds of others, some of them very plentiful and some very rare. There are also metals such as nuggets of pure gold and veins of silver. There are ores, such as rosy red. hematite, a mixture of stone and iron. Also hidden among the rocks of the earth's crust are a few crystals such as diamonds, emeralds and beautiful beryls.
Mother Nature used only a few ingredients to make these countless different substances. The ingredients are called the chemical elements and about 90 of them were used to make the whole earth, everything in it, on it and above it. Some of these elements are so rare that only a few spoonsful of them exist in the whole world. A few elements are very plentiful and they were used to make all kinds of things,
As a rule, we do not find great masses of a pure element in the earth's crust. Nuggets of the element gold are few and far between. The element iron is almost always found mixed with other elements such as oxygen. The element aluminum is very plentiful but it is always mixed with clay or rock. Nature plays a game of hide and seed with these useful elements. If we want them, we must hunt and work for them.
The most plentiful element in the world is oxygen. We know it as the life‑giving gas we breathe from the air. Of every 100 bushels of air, about 21 bushels are oxygen. But not all the world's oxygen is found floating around free in the air. Far from it. Most of it is combined with other elements to make liquids and solids. In these forms, we eat it with our food, drink it with our water, wash in it, swim in it and even stand on it. For the element oxygen is combined with more than half of the different rocks of the earth’s crust.
Altogether, the rocks of the earth's crust have a terrific weight. Nearly one‑third of this weight comes from the element oxygen. The elements iron and nickel, the bulk of which is supposed to be in the core of the earth, make up another third of the earths s total weight. Most of the earth's weight is made from various combinations of the elements oxygen, iron, nickel, cobalt, magnesium and the silica from which sand is made. All the other elements together make up less than five pounds in every hundred pounds of the earths total weight.