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Minerals, Rocks, and Soil Minerals, a Science A–Z Earth Series Word Count: 1,748 Rocks, and Soil

Minerals, Rocks, and Soil Minerals, a Science A–Z Earth Series Word Count: 1,748 Rocks, and Soil

Minerals, Rocks, and , A Science A–Z Series Word Count: 1,748 Rocks, and Soil

Written by Rachel Kamb

Visit www.sciencea-z.com www.sciencea-z.com Key elements Used in This Book Minerals, Rocks, The Big Idea: Earth is made up of various living and nonliving materials. Elements form minerals, and minerals form rocks. Each and can be classified in many ways. Igneous, sedimentary, and metamorphic rocks form differently and can transform through the . Through and Soil and , rocks change, break, and move. Minerals mix with organic material, forming the soil on which and 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, , , , inorganic, lava, magma, matter, metal, , mine, mineral, , organic, process, raw material, refine, resources, rock, rock cycle, sedimentary rock, soil, subsoil, topsoil, weathering Key comprehension skill: Main idea and details Other 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 knowledge Other suitable reading strategies: Ask and answer questions; summarize; visualize; retell

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

Minerals, Rocks, and Soil © Learning A–Z www.sciencea-z.com Written by Rachel Kamb All rights reserved.

www.sciencea-z.com Introduction

Earth provides everything you need to stay alive. It has for drinking and air for breathing. It is home to plants and animals, which you need for so many reasons. But Table of Contents don’t forget one more important thing Earth Introduction...... 4 provides: land!

Elements and Minerals...... 5 The land is where you walk and where you Rocks...... 7 play. Your home is built on land. But what is land made of? Why is it important? In Rock Groups...... 9 this book, you will learn about nonliving Igneous Rocks...... 9 Earth materials that make up the land. Sedimentary Rocks...... 11 Metamorphic Rocks...... 13 Nonliving Earth The Rock Cycle...... 14 materials differ a lot from one Weathering and Erosion...... 15 place to another. What Is Soil?...... 17 They come in Kinds of Soil...... 18 many colors, Layers of Soil...... 19 shapes, and sizes, and can change Using Earth’s Resources...... 21 quite a bit. They Conclusion...... 22 also help you in Glossary...... 23 ways you may This home and the land it sits on are not realize. Index...... 24 made of nonliving Earth materials. 3 4 Elements and Minerals elements → minerals → rocks

To start thinking about what Earth is made A mineral is a natural of, let’s start small . . . really small. Elements substance made of elements.

are what make up all matter, both living and Some minerals, including Silver is a mineral nonliving. Everything on Earth many kinds of metal, consist made of one element. is made from just over one of just one kind of element. For example, silver hundred different elements. is only made of silver, and is only made , helium, and zinc of iron. Many other minerals consist of two are a few of these elements. or more elements. For example, is made of the elements and oxygen. elements → minerals → rocks Earth has nearly 4,000 different minerals. Each one has its own mixture of elements. Periodic table of the elements All minerals are solid, and they form in a pattern of crystals. Minerals have crystals Sr because their atoms are arranged in tidy Cs Cesium patterns. Different Ds Rg Cn Fl Lv Darmstadtium Roentgenium Copernicium Flerovium Livermorium patterns make different crystal

This table lists all the known elements on Earth. Each box shapes. Minerals has a symbol for the element and more information about it. are also inorganic. This means they are not living, Elements are not the smallest parts and they were of matter. The tiniest bits of each never alive. Quartz is made of two elements. element are called atoms. Can you see the pattern made by the minerals? 5 6 Rocks You can describe a rock in many ways. You can also compare one rock with another. Read What happens when minerals combine? the chart to learn some ways to describe and A rock is a hard, solid material found in compare rocks. . Most rocks are made of different minerals, just as a salad is made of different How to Describe and Compare Rocks vegetables. If you pick up a rock, you might Mineral Rocks have a special mixture of one see several colors and patterns. These are composition or more minerals. usually bits and pieces of different minerals. Rocks can be huge or small The mix of minerals in one kind of rock helps Size . They can be as big as a you tell it apart from other kinds of rocks. mountain or as tiny as a speck of dust. elements → minerals → rocks Rocks can be flat, round, square, Shape or almost any other shape.

Rocks come in every color you can imagine. Many rocks have more than Color one color, depending on the colors of their minerals. Some rocks feel very rough, while others are smooth. They can have tiny grains; Texture large, smooth chunks; or long, pointed crystals. Some rocks are full of airholes. The Mohs Scale of Hardness compares how hard each mineral is within a Hardness rock. Talc is rated a 1 (very soft), and diamonds are rated a 10 (very hard). Rocks may have streaks, waves, or straight lines. They may have dots Patterns everywhere or be built layer upon layer. Some rocks do not have a clear pattern. Each rock is made up of a certain mixture of minerals. An important way to describe a rock is by where in nature it is found. A Location may have different rocks than a forest, , or volcano.

7 8 Rock Groups Igneous rocks can be very different from When you think of “rock groups,” you might one another. The imagine loud music. But Earth has its own size of the crystals kinds of rock groups. Every rock belongs in in an igneous rock one of three groups, based on how it formed. Pumice is full of tiny airholes. It’s is determined by so light that it can float in water! Let’s take a closer look at each rock group how fast the magma cools and turns solid. and how it forms. If lava cools quickly on the surface, it does Igneous Rocks not have time to grow large crystals. For Boom! A volcano blasts hot, liquid rock, called example, pumice is a rock that cooled magma, from beneath Earth’s . The magma, quickly. It is made of tiny glass crystals. which is called lava above the ground, cools on When magma cools slowly underground, the surface, making igneous rocks (IG-nee-us). the extra time allows larger crystals to form. Other igneous rocks form as magma cools , which cools slowly, is hard and underground. VOLCANO very solid. It has large crystals made of

lava igneous rocks several minerals.

To remember how Obsidian forms igneous rocks when magma form, think cools very of the word quickly. It looks ignite, which like black glass. means “to start a fire.” Igneous rocks start magma off very hot and then cool down. Granite is used for kitchen counters and in the walls of some buildings.

9 10 Sedimentary Rocks may be found in Some rocks are made from tiny bits of minerals sedimentary rocks. Millions called . Because sediment is so small, of years ago, dead plants and water and wind can easily move it and deposit animals settled at the bottom it in different locations. can build of , rivers, and . up, layer upon layer. Older sediments at the Over time, layers of sediment fossilized leaf bottom become compacted as newer layers buried the plants and animals, forming build up above sedimentary rocks. The plants and animals, them. Over or imprints of them, sometimes hardened a long and remained in the rock. These are fossils. period of time, all Look for fossils where that weight ancient , lakes, and pressure or rivers used to be. is a type of A fossil can help you create sedimentary rocks. sedimentary rock. learn about what Sedimentary rocks are often the easiest rocks once lived in an area. to break apart. They are made up of bits of You can also compare rock that have been pressed together, not those plants and melted together like fossilized dinosaur footprint animals with the ones igneous rocks. Some that live there today. sedimentary rocks, such as , is a sedimentary rock mostly can crumble when made of the element carbon, which is found in living material. Over you walk on them. When you look at a side view millions of years, pressure turned But others are strong. of sedimentary rock layers, you the living material into rock. are seeing a slice of history. 11 12 The Rock Cycle

The word metamorphic comes from the Greek Plants and animals change during their word metamorphosis, which means “to change.” cycle. Water changes as it moves through the How are a butterfly and a metamorphic rock alike? water cycle. Rocks change, too. In fact, any of the three kinds of rocks can change into one Metamorphic Rocks of the other kinds. The rock cycle describes Metamorphic rocks (met-uh-MOR-fick) form the process that rocks go through as they when a rock changes due to heat and pressure. change from one kind to another. Study the Igneous, sedimentary, and metamorphic rocks diagram to learn how any kind of rock can can all end up deep below Earth’s surface. change into any other. There, Earth’s heat and the pressure caused by the heavy rocks above them makes them igneous ering and eros rock ath ion change more. we sedimentary rock A sedimentary rock can be very weak. But after the rock cycle it has been heated and placed under additional pressure, it can become a metamorphic rock, melting

he such as . Marble is very strong, so it is a t n a io n s often used in buildings d ro

p e e r d r e n u and statues. s a s s s u g e r n r i e p r m e d h n e t a l a ti t n e a g e w h

Phyllite (left) and (right) are two examples of metamorphic rocks. metamorphic rock 13 14 Weathering and Erosion

Rocks can also change without becoming a new kind of rock. They can change shape or size. They can also move from one place to another.

Weathering makes rocks change. Sometimes they change shape or size. Wind and water make rocks bang into each other. They might become smooth and round or break An arch caused by weathering A rockslide caused by erosion into pieces. Water can seep Weathering changes rocks, but erosion moves into cracks in a rock and them to a new place. Forces such as wind and freeze, breaking the rock. water carry the loose pieces of rock and deposit A ’s roots might grow them somewhere else. As some rocks move, into a crack in a rock. As A tree is splitting a rock. This is an example of they create more erosion by making other rocks the crack expands, pieces mechanical weathering. move. Large boulders can break into smaller of the rock may break off. rocks, stones, pebbles, , or even dust. The chemicals in rocks can Other forces cause erosion, too. Moving ice in change, too. Minerals may a slowly carries loose rocks downhill. fall apart or dissolve when Earthquakes or heavy rain can cause landslides, they mix with water or other in which loose rocks tumble due to gravity. chemicals. Acid from plants People can cause erosion by using machines can change rocks, too. When Acid rain has changed to cut through rock and haul it away. Even a rock’s chemicals change, the minerals in this gravestone. This is an wildfires can cause erosion by removing the it may get weak or crumble. example of chemical weathering. vegetation that holds rocks in place. 15 16 What Is Soil? Kinds of Soil

Earth isn’t just covered with broken rocks and There are thousands of minerals. The land also has a lot of organic kinds of soil around the matter. This material is living or once was world. Each one is made alive. It includes rotting plants, dead animals, up of a unique combination and waste. The mixture of rocks, of minerals, bits of rock, minerals, and is called soil. and organic material.

and min soil anic mat s er rg te ck a o r It can take hundreds ls ro or thousands of years for each kind of soil to form. Because of all the possible mixtures, soil Soil also contains air between all the bits comes in many colors of solid material. Most contain some and textures. Some soils amount of water, too. are dense, or packed together tightly. Others The organic matter in soil is called humus are packed more loosely. (HYOO-muss). It is full of nutrients. Plants rely on the air, water, and nutrients in soil to grow and to live. Many animals eat Soil scientists have those plants. So you identified over 10,000 different have soil to thank kinds of soil in for the foods you eat. Europe alone.

17 18 Layers of Soil One good way to describe soil is by its texture. Scientists also measure Just like rocks, soil changes and moves. how compact, or Weathering and erosion affect soil most pressed together, the on the surface. As a result, soil often forms soil is. They describe in different layers. the soil’s color and sand The thin layer found on most of Earth’s land temperature, too. They is called topsoil. It is often soft and rich in may even find out organic material. It usually contains more how much water, air, air and water than the deeper layers. and humus it contains. loam

The middle layer is called subsoil. It tends to Sand feels gritty, while silt is made of smaller be drier and harder than topsoil and contains bits and feels powdery like flour. Clay is made more rocks. of even smaller bits mixed with water, so it Cutaway View of Soil Layers feels sticky. Loam is a mixture of sand, silt, Bedrock is usually Science clay, and organic matter. far below the In Your surface. Here, In the last 200 years, the World has lost from 25–70 percent of its weathering and topsoil due to farming, logging, and grazing. erosion have not topsoil With fewer plants, topSoil Loss per year changed the rock soils have been in the United States subsoil eroded by wind much. Less water and water and and air can reach have washed it, so bedrock is down rivers and streams. often very hard bedrock and dry. n Low n Moderate n High n Very High

19 20 Using Earth’s Resources Conclusion

We use for , tiles for floors, and oil Elements make up minerals, and minerals for energy. We use bricks for buildings, glass make up rocks. Rocks form in different for windows, and metal for cars. When we ways. They can be igneous, sedimentary, use Earth’s materials, we call them resources. or metamorphic. Over time, each kind of Some resources are deep below Earth’s surface. rock can change into one of the other kinds. To reach them, people mine, dig, drill, or blast Weathering and erosion make rocks change into the land. and move. As rocks break down, they can Most of Earth’s resources cannot be used in mix with organic matter to form soil. Earth their natural form. These raw materials have has countless kinds of rocks and soils. Plants to be processed or refined. For example, most and animals rely on healthy soil. metals are found mixed with other minerals People use Earth’s resources to make and in a rocky substance called ore. Machines build things. Some resources are in limited process the ore to sort the metals, such as supply, so it is important that we use Earth’s copper and silver. They also remove unwanted materials wisely. minerals. Coal and oil are important energy resources. Factories refine them before they can power our cars and heat our homes.

Mining for metals Drilling for oil

21 22 Glossary mineral a solid, natural material that does not come from a living crystals minerals that form in regular, thing (p. 6) tight patterns (p. 6) resources supplies of things that are deposit to set down one or more layers valuable or very useful to of material in a new place, people (p. 21) as water or wind can do to rock a hard, solid material that sediment (p. 11) is made of minerals and is elements pure substances; the building found in nature (p. 7) blocks of everything on Earth rock cycle the series of changes that rock (p. 5) undergoes as it shifts between erosion the process of transporting and different types (p. 14) wearing away rocks or soil as sedimentary rocks formed when sediment is loose particles are moved by rocks pressed together over time (p. 11) water, wind, ice, or gravity (p. 16) soil the top layer of the ground, in fossils the remains of plants or animals which plants grow; dirt (p. 17) that turned to stone over a long period of time (p. 12) weathering the process of wearing away or otherwise changing Earth’s igneous rocks formed by the cooling and surface, caused by natural rocks hardening of hot magma or lava forces (p. 15) (p. 9) metal a material, usually hard and Index shiny, that allows electricity and heat to move through it (p. 6) atoms, 5, 6 Periodic Table of metamorphic rocks formed when any type coal, 12, 21 the Elements, 5 rocks of rock goes through changes humus, 17, 20 sediment, 11, 12 caused by extreme heat and lava, 9 soil layers, 19 pressure (p. 13) magma, 9, 10 weathering, mechanical ore, 21 vs. chemical, 15 23 24

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