Rock is the commonest thing in the world. And to many of us it seems the most solid and enduring. Yet all around us we see evidence that rocks are constantly changing. At the seashore we see great stretches of sand which the waves have worn from the rocks. On the highway a sign warns us "Beware of falling rocks," and we know that bits of the mountain are weathering off. Or we may see a great boulder perched in the middle of a cow pasture and find that a glacier carried it to this spot a million years ago.
But although mountains wear away, new ones always build up again. For rock is made as well as unmade. A volcano, for example, builds itself up with lava coming from deep within the earth. But some of our mountains have been created by great pressures within the earth that have caused layers of rock to split or tilt or even to push above the earth's surface.
And always this change is creating different kinds of rock. Some is as shiny as any glass we manufacture. Some sparkles with flecks of minerals. Some is as soft as chalk. Some is in six-sided crystals. And some shows the pattern of the tiny seashells from which it is made.
In All About Our Changing Rocks, Anne Terry White tells of the vast changes that have produced these different rocks and explains how to identify the rocks we see around us.
—from the dust jacket
An extensive and satisfying survey by a recognized non-fiction writer, this seems a better coverage than Carroll and Mildred Fenton's first geology books and about equal in content to Rocks, Rivers and the Changing Earth, by Nina and Herman Schneider. It starts with rocks as the source of a great percentage of the Earth's materials, and the early thoughts about rock formation—Werner's layer theory and Hutton's more advanced one that rocks are made and unmade by a variety of interactions. Following chapters discuss the different kinds of rock—from pebbles to mountains—what they contain and how they are formed. Boulders, falling rock, volcanoes, sea floor sediment, identifying minerals, granite, salt, and fossil containing rock are a few of the other topics that give us a friendly introduction to geology here.
Did you find this review helpful?