Visit www.sciencea-z.com

Minerals, Rocks, and Soil

A Science A–Z Earth SeriesWord Count: 1,000

www.sciencea-z.com

Written by Rachel Kamb

Minerals, Rocks,

and Soil

Written by Rachel Kamb

www.sciencea-z.com

Minerals, Rocks, and Soil © Learning A–Z Written by Rachel Kamb

All rights reserved.

www.sciencea-z.com

KEY ELEMENTS USED IN THIS BOOKThe Big Idea: Earth is made up of various living and nonliving materials. Elements form minerals, and minerals form rocks. Each mineral and rock can be classified in many ways. Igneous, sedimentary, and metamorphic rocks form differently and can transform through the rock cycle. Through weathering and erosion, rocks change, break, and move. Minerals mix with organic material, forming the soil on which plants and animals rely. People use nonliving materials as resources by mining, drilling, and refining them. While seemingly abundant, Earth’s resources are limited and must be preserved for future generations.Key words: bedrock, crystal, deposit, drill, element, energy resources, erosion, fossil, humus, igneous rock, inorganic, lava, magma, matter, metal, metamorphic rock, mine, mineral, ore, organic, process, raw material, refine, resources, rock, rock cycle, sedimentary rock, soil, subsoil, topsoil, weathering

Key comprehension skill: Main idea and detailsOther suitable comprehension skills: Compare and contrast; classify information; cause and effect; identify facts; elements of a genre; interpret graphs, charts, and diagrams; using a glossary and boldfaced terms; using a table of contents and headings

Key reading strategy: Connect to prior knowledgeOther suitable reading strategies: Ask and answer questions; summarize; visualize; retell

Minerals, Rocks, and Soil

Photo Credits: Front cover (tl): © iStockphoto.com/Gilles Glod; front cover (tc), pages 7, 8 (3), 20 (tcl, tcr): Casey Jones/© Learning A–Z; front cover (tr): © iStockphoto.com/malerapaso; front cover (cl): © iStockphoto.com/ Martin Novak; front cover (c): © iStockphoto.com/Jakub Krechowicz; front cover (cr), page 8 (1): © iStockphoto.com/ Fabrizio Troiani; front cover (bl): © Igor Baz/123RF; front cover (bc): © iStockphoto.com/Jacob VanHouten; front cover (br): © iStockphoto.com/Jill Fromer; front cover (background): © iStockphoto.com/Selahattin Bayram; back cover, page 8 (4): © iStockphoto.com/Jodi Jacobson; title page: © iStockphoto.com/Agnes Csondor; page 3: © iStockphoto.com/hsvrs; page 4: © iStockphoto.com/Jason Floyd; page 5 (top): © Jelena Zaric/123RF; page 6 (top): © iStockphoto.com/Don Wilkie; page 6 (b): © iStockphoto.com/Rainer Walter Schmied; pages 8 (2), 20 (tl): Doug Tepper/© Learning A–Z; page 8 (5): © iStockphoto.com/Nikola Miljkovic; page 8 (6): © iStockphoto.com/Max Delson Martins Santos; pages 8 (7): © iStockphoto.com/stockcam; page 8 (8): © iStockphoto.com/Anandha Krishnan; page 9: © DK Images; 10 (t): © O. Diez /Arco Images GmbH/PhotoLibrary; page 10 (bl): © iStockphoto.com/Ross Chandler; pages 10 (br), 14 (tl): © iStockphoto.com/Sean Curry; pages 11 (t), 13 (b),14 (tr): © iStockphoto.com/Tyler Boyes; page 11 (b): © iStockphoto.com/Stephen Morris; page 12 (t): © iStockphoto.com/clu; page 12 (c): \© iStockphoto.com/Chanyut Sribua-rawd; page 12 (b): © iStockphoto.com/Daniel G. Mata; pages 13 (t), 16 (l): \© Jupiterimages Corporation; page 14 (b): © iStockphoto.com/Kime Veruss; page 15: © iStockphoto.com/\Radu Razvan; page 16 (r): © iStockphoto.com/Thierry Roy; page 17 (bl): © iStockphoto.com/Valeriy Novikov; \pages 17 (bc), 20 (tr): © iStockphoto.com/Mark Wragg; page 17 (br): © iStockphoto.com/Thomas Osborne; page 17 (t): © iStockphoto.com/Geoff Hardy; page 18 (t to b: 1, 2): © iStockphoto.com/Bart Coenders; page 18 (3): © iStockphoto.com/Barıs5 Muratoglu; page 18 (4): © iStockphoto.com/Kadir Barcin; page 18 (5): © iStockphoto.com/AdShooter; page 19: © Design Pics Inc./Alamy; page 21 (l): © iStockphoto.com/ Taylor Hinton; page 21 (r): © iStockphoto.com/hh5800; page 22 (t): Gawain Douglas/© Learning A–Z; page 22 (b): © iStockphoto.com/Morgan Lane Studios

Illustration Credits: Pages 5 (bottom), 20 (bottom): Casey Jones/© Learning A–Z

3

Introduction

Earth has everything you need to stay alive. It has water, air, plants, and animals. Earth also has land!

Land is where you walk and play. Your home sits on land, too. What is land made of? Why is it important? In this book, you will learn about nonliving Earth materials that make up the land.

Nonliving materials come in many colors and shapes. They come in many sizes, too. They can change in many ways.

4

Houses sit on land.

Table of Contents

Introduction ...................................... 4Elements and Minerals .................... 5Rocks .................................................. 7Rock Groups ..................................... 9 Igneous Rocks ................................. 9 Sedimentary Rocks ........................ 11 Metamorphic Rocks ...................... 13The Rock Cycle ............................... 14Weathering and Erosion ................ 15What Is Soil? ................................... 17Kinds of Soil .................................... 18Layers of Soil ................................... 19Using Earth’s Resources ................ 21Conclusion ...................................... 22Glossary ........................................... 23Index ................................................ 24

Elements and Minerals

Let’s start with elements. They make up everything on Earth. They are very, very small.

5 6

A mineral is made of elements. Minerals are solid and inorganic. They were never alive.

Some minerals have just one element. For example, silver is just made of silver. Iron is only made of iron. Other minerals, such as quartz, have two or more elements. Earth has about 4,000 kinds of minerals. Each mineral has its own mix of elements.

elements → minerals → rocks

Elements are not the smallest parts of matter. The tiniest bits of each element are called atoms.

This table lists all the known elements on Earth. Each box

has a symbol for the element and more information about it.

elements → minerals → rocks

PERIODIC TABLE OF THE ELEMENTS

silver

quartz

Sr

Darmstadtium

DsRoentgenium

RgCopernicium

CnFlerovium

FlLivermorium

Lv

Cesium

Cs

Rocks

A rock is made of minerals. It is hard, solid, and natural. A rock can have many colors and patterns. The bits and pieces of minerals give a rock its colors and patterns.

7

Look at the chart. It shows you many ways to compare rocks.

8

Each rock has a mixture

of minerals in it.

HOW TO DESCRIBE AND COMPARE ROCKS

elements → minerals → rocks

Mineral composition Rocks have a special mix of minerals.

Size

Rocks can be huge boulders or small pebbles. They can be as big as a mountain or as tiny as a speck of dust.

ShapeRocks can be flat, round, square, or almost any other shape.

Color

Rocks come in every color you can imagine. Many rocks have more than one color. It depends on the colors of their minerals.

Texture

Some rocks are rough, while others are smooth. They can have tiny grains or large, smooth chunks. Some have long crystals. Others are full of airholes.

Hardness

The Mohs Scale of Hardness compares how hard each mineral is within a rock. Talc is rated a 1 (very soft), and diamonds are rated a 10 (very hard).

Patterns

Rocks may have streaks, waves, or lines. They may have dots or be built layer upon layer. Some rocks do not have a clear pattern.

Location

An important way to describe a rock is by where you find it. A beach may have different rocks than a forest, desert, or volcano.

Think of igneous rocks as fire rocks. They come from super-hot rocks.

igneous rocks lava

9

Rock Groups

Earth has three rock groups. Each rock group forms in a different way. Let’s learn about each group.

Igneous Rocks Hot, soft rock called magma lies underground. When magma blasts out of a volcano, it is called lava. As magma and lava cool, they turn into igneous rocks (IG-nee-us).

10

Sometimes lava cools fast on Earth’s surface. The cooled rocks might become pumice. These rocks are full of tiny airholes.

Sometimes magma stays underground and cools slowly. This cooled rock might become granite. It is hard and solid.

magmaGranite is used in kitchens and to build some walls.

Obsidian forms when magma cools very quickly. It looks like black glass.

Pumice is so light

that it floats in water!

VOLCANO

Look for fossils in sedimentary rocks. Millions of years ago, dead plants and animals settled to the bottom of seas, lakes, or rivers. Layers of sediment buried the plants and animals. Then rock formed.

Sedimentary Rocks Some rocks are made from tiny bits of minerals called sediment. Water and wind can move the very small pieces. Then the bits settle to Earth in layers. New layers form on top of old layers. Weight and pressure make the layers press together. Over a long time, sediments turn into sedimentary rocks.

Sandstone is a sedimentary rock. It is easy to break.

11 12

Coal is a sedimentary rock made of dead plants pressed together. Over millions of years, under great pressure, the plants turned into rock.

Look at a side view of

sedimentary rock. You are

seeing a slice of history.

Fossil of a leaf

Fossil of a dinosaur footprint

The plant or animal stayed in the rock, or its shape did. Fossils help you learn about the plants and animals that once lived there.

Breccia is a type of sedimentary rock.

13 14

Metamorphic Rocks Heat and pressure deep below Earth’s surface can change older rocks. They become metamorphic rocks (met-uh-MOR-fick). A weak rock might turn into a strong rock.

The Rock Cycle

Rocks go through a rock cycle. They move up to Earth’s surface. They break apart and can get pressed together again. They go underground, where heat and pressure can change them.

Look at the diagram. It shows how rocks can change from one kind to another.

The word metamorphic comes from a Greek word that means “to change.” Why are some rocks called metamorphic?

Phyllite (top) and gneiss

(bottom) are two kinds

of metamorphic rocks.

THE ROCK CYCLE

igneous rock sedimentary

rock

metamorphic rock

w

eathering and erosion

heat

and

pre

ssur

e

melting

melting

heat and pressure

wea

ther

ing

and

eros

ion

16

Weathering and Erosion

Rocks can change and move. Weathering changes the size and shape of rocks. Moving water and wind often make rocks bang into each other. This makes the rocks smooth and round. It can also break the rocks into pieces.

Water can get into the cracks in a rock. In winter, the water may turn to ice. The ice can open the crack and break the rock into pieces.

Plant roots can grow into a crack, too. As they grow, they can break the rock open.

15

Erosion moves rocks. Wind and water can move small pieces of rock from one place to another. As the rocks move, they bump into other rocks and move or break them. This causes more erosion. Big rocks can turn into stones, sand, or even dust.

Other things move rocks, too. Glaciers carry rocks downhill in a slow river of ice. Earthquakes or heavy rain can make rocks tumble down mountains.

A tree is splitting a rock. This is

just one example of weathering.

An arch caused by weathering

A rockslide caused by erosion

ro

cks and minera

ls

org

anic matter

soil

Kinds of Soil

The world has many kinds of soil. Each kind has a different mix of minerals, bits of rock, and humus. It can take many years for each kind of soil to form.

Soil comes in many colors. One soil may not feel the same as another one. Soil can be packed tightly or loosely.

18

What Is Soil?

Earth’s land is more than nonliving rocks and minerals. Land also has organic matter that is alive or once was alive. Plants, dead animals, and animal waste are organic. Soil is a mix of rocks, minerals, and organic matter. The organic matter in soil is called humus (HYOO-muss).Soil also has air and water. Plants need soil, and many animals eat plants.

17

Soil scientists have found over 10,000 different kinds of soil in Europe.

Texture is how something feels. It is one way to describe soil.

Sand feels gritty because of its hard bits of rock. Silt feels like flour. It is made of bits that are smaller than sand. Clay feels sticky. It is made of even smaller bits mixed with water.

19 20

Layers of Soil

Soil changes and moves near the surface. It changes less underground. As a result, soil often has layers.

The thin layer on top is topsoil. It is often soft. It usually has more air and water than deeper soil.

Subsoil is the middle layer. It is drier and harder than topsoil. It has more rocks.

Bedrock is often far underground. Little air or water reaches bedrock. It is often very hard and dry.

The United States has lost a lot of topsoil. This is because of farming,

logging, and grazing. With fewer plants, wind and water cause more soil erosion.

Science In Your World

Science In Your World

LowModerateHighVery High

TOPSOIL LOSS PER YEAR IN THE UNITED STATES

sand silt clay loam

CUTAWAY VIEW OF SOIL LAYERS

topsoil

subsoil

bedrock

21 22

Using Earth’s Resources

When we use rocks, minerals, and soil, they are called resources. Some resources are deep below Earth’s surface. People mine, dig, drill, or blast the land to get to them.

Many metals we use are found inside rocks. People use machines to get out the important metals. Other Earth resources can be used for energy. They help move cars and heat homes.

Conclusion

Elements make up minerals. Minerals make up rocks. Rocks can be igneous, sedimentary, or metamorphic. Rocks can change from one kind to another

in the rock cycle.

Weathering and erosion change and move rocks. Rocks mix with organic matter to make soil.

People need Earth’s resources. We make and build things with rocks and minerals. We grow food in soil. So we need to use resources wisely.

Drilling for oilMining for metals

23 24

Glossaryelements pure substances; the building

blocks of everything on Earth (p. 5)

erosion the process of transporting and wearing away rocks or soil as loose particles are moved by water, wind, ice, or gravity (p. 16)

fossils the remains of plants or animals that turned to stone over a long period of time (p. 12)

igneous rocks formed by the cooling rocks and hardening of hot magma or lava (p. 9)metals materials, usually hard and

shiny, that allow electricity and heat to move through them (p. 21)

metamorphic rocks formed when any type rocks of rock goes through changes

caused by extreme heat and pressure (p. 13)

mineral a solid, natural material that does not come from a living thing (p. 6)

resources supplies of things that are valuable or very useful to people (p. 21)

rock a hard, solid material that is made of minerals and is found in nature (p. 7)

rock cycle the series of changes that rock undergoes as it shifts between different types (p. 14)

sedimentary rocks formed when sediment rocks is pressed together over time

(p. 11)soil the top layer of the ground,

in which plants grow; dirt (p. 17)

weathering the process of wearing away or otherwise changing Earth’s surface, caused by natural forces (p. 15)

Indexatoms, 5coal, 12humus, 17, 18lava, 9, 10magma, 9, 10

Periodic Table of the Elements, 5sediment, 11, 12soil layers, 19