GenreGenre Comprehension SkillComprehension Skill Text FeaturesText Features Science ContentScience Content Nonfi ctionNonfi ction Compare andCompare and • Captions• Captions Rocks and SoilRocks and Soil ContrastContrast • Diagrams• Diagrams • Labels• Labels • Glossary• Glossary Scott Foresman Science 3.7Scott Foresman Science 3.7 ì<(sk$m)=bdichc<ì<(sk$m)=bdichc<ISBNISBN 0-328-13827-40-328-13827-4 +^-Ä-U-Ä-U+^-Ä-U-Ä-U
Vocabulary What did you learn? decay igneous rock 1. Which kind of rock forms in layers? loam metamorphic rock 2. What are three ways that minerals mineral are described? nutrient rock 3. What are some ways minerals help sedimentary rock you to stay healthy? soil 4. On page six, you read about metamorphic rock. Write to explain how metamorphic rock forms from limestone, based on what you have read.by L. L. Owens 5. Compare and Contrast How does soil with a lot of clay compare Picture Credits Every effort has been made to secure permission and provide appropriate credit for photographic material. to soil with a lot of sand? The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd). Opener: Getty Images; 2 Getty Images; Backgrounds: Getty Images. Scott Foresman/Dorling Kindersley would also like to thank: 2 (CR), 8 (CR, BC), 9 (CL, BR), 12 (CR) Natural History Museum, London/DK Images. Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson. ISBN: 0-328-13827-4 Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05
Rocks Are Everywhere Groups of Rocks Rocks are solid objects that come in all Scientists group rocks by their color, texture, different shapes and sizes. Have you ever wondered and minerals. Rocks are also grouped by how what our planet’s rocks are made of? Rocks are they formed. made mostly of minerals. A mineral is a natural Igneous rock comes from a mixture of substance that is made of nonliving matter. melted minerals and gases deep inside the Rocks have different colors and textures ground. This blazing hot mixture cools and depending on the minerals in them. A rock hardens as it moves toward the surface. If the can be made of just one mineral solid rock cools quickly, its mineral grains can or of many different minerals. be large. But if the solid rock cools slowly, A rock’s texture is the its mineral grains can be too small to see. size of the bits of minerals, or grains, within it. A rock’s Shape, color, and color depends on the kind texture can indicate of minerals and other rock type. substances that are in the rock. Granite Gabbro Ironstone 2 3
Obsidian When water travels over the land, it picks up small bits of broken rock. When these bits of rock settle on the bottom of lakes, rivers, and oceans, they are called sediment. Over thousands of years, pressure can bind bits of sediment together. This turns the sediment into sedimentary rock. The remains of dead plants and animals can be buried under layers of Snowfl ake sedimentary rock. After many years, these remains Fern fossil obsidian can turn into stone. Then the remains are called fossils. One kind of igneous rock is obsidian. The cliffs of the Grand Canyon, in Arizona, show layers of Fish fossil Obsidian is dark, smooth, glassy, and very hard. sedimentary rock. It forms when melted rock cools very quickly. It can be used to make tools. Some obsidian stones have white designs on the surface where crystals formed. The designs look similar to snowflakes. Those rocks are called snowflake obsidian. 4 5
The third rock group is called metamorphic When rocks melt, they mix, cool, and harden rock. Metamorphic rock is igneous or to form new igneous rock. When rocks are worn sedimentary rock that has changed over a long down, the remains form new sedimentary rocks. time into a new kind of rock. Limestone is Under the right conditions, both igneous and a sedimentary rock. Limestone becomes marble sedimentary rocks can become metamorphic rock. when it is heated and pressed for many years. Marble is a metamorphic rock often Lava cools to form Where Rocks Form igneous rock on the used in building. slopes of volcanoes. Rock particles are carried Examples of Metamorphic Rock by rivers into the sea, where they form sedimentary rock. Slate Marble Gneiss Under pressure, igneous and sedimentary rock can form metamorphic rock. Marble, a metamorphic rock, is often used to make fl oors. 6 7
More About Minerals Minerals are the most common solid material on Streak is the color of the mineral in its Earth. Almost everything we use contains minerals. powder form. You can find a mineral’s streak Scientists can tell minerals apart by looking at by rubbing the mineral across a hard surface. things such as color, streak, hardness, and luster. The color of a mineral’s streak is always the Color is the easiest to notice. Some minerals come same. This is true even if the mineral itself in different colors. Spinel, for example, is a mineral comes in different colors. that can be red, lavender, blue, green, brown, Pyrite is a mineral. It is called “fool’s gold” or black. The most common variety of because it is often confused with gold. Pyrite’s spinel is a clear red. streak is black. Real gold has a yellow streak. The minerals quartz and spinel cling to this rock. Molybdenite streak Molybdenite Red spinel Quartz Spinel Gold Pyrite 8 9
Minerals in Our Lives Hardness is how easily a mineral can be scratched. We depend on minerals. When you turn Hardness is measured on on a lamp, you are using copper, quartz, and a scale of one to ten. One wolframite. The copper is in the electrical wiring. is the softest and ten is the Quartz is found in the glass of the lamp’s bulb. hardest. The hardest mineral Wolframite is in the metal wire of the bulb. is diamond. It cannot be Anything made of glass has quartz in it. Diamond scratched by anything You will find quartz in drinking glasses, TVs, but another diamond. radios, and clocks. Quartz is one of the most Luster describes how common minerals on Earth. a mineral reflects light. Gold, platinum, and silver are all minerals with a metal-like luster. The most common luster is glassy. Platinum Amethyst has a glassy luster. Quartz The wires inside a Amethyst light bulb are made with wolframite. The bulb’s glass contains quartz. Wolframite Electrical wires are made of copper. Copper 10 11
To stay healthy, your body needs minerals every day! When you sprinkle salt on food, you are using the mineral halite. The iron in meat helps your red blood cells. Chromium is a mineral that may help prevent a disease called diabetes. Calcium and magnesium are important From Rocks to Soil minerals for your body. Calcium builds bones and teeth. Magnesium helps muscles tighten Soil is the thin layer of loose material that and relax. covers most of the land on Earth. Plants, animals, and people all depend on soil. Soil is made up of water, air, bits of rock, and Salt nutrients. Nutrients are materials that plants need to help them grow. Some nutrients are the remains of living plants and animals that have broken down through a process called decay. Other nutrients come from the minerals in the soil. Halite, or salt Rabbits depend on soil for food and shelter. Toothpaste contains calcium carbonate. Calcium carbonate, or chalk 12 13
Kinds of Soil Soil forms in layers. The top layer is called topsoil. It contains many nutrients. Below the Humus topsoil is subsoil, where tree roots find their water. The deepest layer is bedrock. As bedrock gets broken Topsoil down, it becomes soil. Loam Humus is found in soil. It is made of decaying Subsoil Loam is a kind of soil plants and animals. made of sand, silt, and clay. Clay is made of small Crops usually grow best in particles. Clay soil is thick, loam because it has the right dense, and traps water. amount of sand, silt, and clay. Sand particles are large and Rocks, minerals, and soil have a lot of space between are everywhere. Without rocks, them. Water passes through minerals, and soil, we wouldn’t sand. Silt has medium-sized Poor soil be able to live. So be sure to with rock particles. It lets the right fragments treat the earth beneath you well! amount of water in and out. Bedrock 14 15
GlossaryVocabulary What did you learn? decay decayigneous rock the process of breaking down 1. Which kind of rock forms in layers? loam the remains of living matter metamorphic rockinto nutrients 2. What are three ways that minerals igneous rockmineral rock that forms when hot, are described? nutrient melted minerals in the center rock of Earth cool down 3. What are some ways minerals help loamsedimentary rocka kind of soil that plants grow you to stay healthy? soil very well in and that contains sand, silt, and clay 4. On page six, you metamorphic rock that forms when igneous read about metamorphic rock. Write rock or sedimentary rock is changed to explain how metamorphic rock by heat or pressure forms from limestone, based on what you have read. mineral a solid substance made naturally from nonliving matter 5. Compare and Contrast How nutrient material that plants and animals does soil with a lot of clay compare Picture Credits need to live and grow Every effort has been made to secure permission and provide appropriate credit for photographic material. to soil with a lot of sand? The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).rock solid matter made of minerals that Opener: Getty Images; 2 Getty Images; Backgrounds: Getty Images.are found in and on Earth Scott Foresman/Dorling Kindersley would also like to thank: 2 (CR), 8 (CR, BC), 9 (CL, BR), 12 (CR) Natural History Museum, London/DK Images.sedimentary rock that forms when layers of Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson. rock broken rock are pressed together soil the thin layer of loose material that ISBN: 0-328-13827-4 covers most of the land on Earth Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 0516
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