This section is from the "The New Student's Reference Work Volume 5: How And Why Stories" by Elinor Atkinson.
Water is very heavy. A little boy or girl cannot carry a wooden pail full of it very far. Every pint of water weighs a pound. The ocean is deep. There are hills and valleys and mountain ranges on the ocean floor, just as there are on land. Some places are as deep as our mountains are high. Tons and tons of water lie over every foot of the ocean floor, and press it smooth and hard. The under layers turn to stone. All the earthy material was sorted, so now it turns to many kinds of stone— sandstone, shale rock and slate. Far out, in the deepest part of the ocean, where sand and mud are never carried, the ocean bed is made of fish bones and shells. These are ground to white powder, by the weight of the water, and turned into chalk or limestone or white marble.
You know what a volcano is, don't you? It is a mountain with a fire in it. That fire comes from the middle of the earth. It lies far under all the land and sea. Sometimes this fire breaks through a mountain top, and it breaks through the floor of the ocean, too. When it does this sandstone is melted, and when it hardens again it becomes granite or lava rock.
There are quarries of all these stones and marbles on the land. If they were made in the bottom of the sea how did they get up on the land? They were pushed up by the fire. The fire melted and cracked and pushed, until the rocky floor of the ocean came up through the water to form rocky islands. A long string of these islands slowly became a mountain chain. In pushing up, the rock layers were broken and folded in many curious ways. In valleys the rock layers rose more evenly. Just as soon as a point of rock rose above the water, rain and wind and frost and, after awhile, plants and animals began to wear it down. Slowly the valleys between the mountains were raised and filled with finely ground rock waste and leaf mold. The water from above gathered into lake bowls and river troughs.
A piece of rock showing the remains of little sea animals which are contained in the rock.
A glass of water taken from the muddy river, to show how the fine particles worn from the stones, settle down on the bottom as a layer of mud.
You see the story of land goes around a circle. Mother earth is all the time tearing down and building up. She doesn't mind spending millions of years in grinding a mountain into mud and sand; pressing these into stone, and lifting the rock layers into mountain chains again. While she is about it, too, she puts gold, silver and copper, iron, lead and tin, salt, sulphur and coal, and many other things, into all the cracks and holes, and between the layers of stone. She hides diamonds and many precious jewels, too. It would take too long to tell here how she does all these things. It took men thousands and thousands of years to find the keys to unlock the prisons of all these useful and beautiful things.
You really ought to know about coal. It was made by pressure under sea water, like stones. But what do you think it was made of? What do you look for to make a fire? Wood! Rocks may melt, but they harden again. Only plants will burn to ashes.
Ages and ages ago, simple plants like moss, with woody stems and no leaves, grew on big, quiet ponds until they covered the water. The moss died below, but did not decay, and it went on growing on top, until a spongy, floating mat many feet thick was formed. There are many such beds of moss today. They make a spongy brown fuel called peat. Peat is burned in Ireland and other countries. Peat would become coal, after a long time, if it sank below the sea, mud and sand or shells settled on it, and the sea water pressed it between layers of rock.
This picture shows a vein or bed of coal as it lies in the earth, with layers of different kinds of rock above and below it.
Every part of this earth story is going on today. Volcanoes still burn, earthquakes still lift and crack and fold the rocky floor of the ocean. You remember the terrible earthquakes we have had. They shook down great cities. The earth under them was lifted a little, or dropped a little. One volcano poured out melted rock, or lava and granite, and buried a city. Some seacoasts are slowly sinking, some rising. Small islands come up or disappear. The valleys are being filled up, the mountains worn down by water, wind, frost, men, animals and plants. Tons and tons of mud and sand are being carried out to the ocean every day, to be turned into stone again. Sea animals are dying, and dropping their bones and shells to the ocean floor.
Isn't it a wonderful story? Don't all these things mean a great deal more to you than they did before? See Geology.
This picture shows a volcano in action. The hollow top is the crater from which rocks and lava have been thrown out, and a stream of lava is flowing down the side.
A bed of peat, showing where it has been cut out and used for fuel; also small stacks of peat piled up to dry.