Suppose you were hiking and found a gleaming chunk of

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1 15. What is the measurement unit for latitude and longitude? 16. What is the line of 0 latitude called? 17. On which line of longitude does a point at 31 S, 92 W He? 18. Which hemispheres lie on either side of the prime meridian? Choose the word or phrase that best completes each sentence. Write the letter of the answer on your paper. 19. The earth rotates from. A east to west C west to east B north to south D south to north 20. The earth rotates once every. A day B week C month D year 21. The time in Europe is the time in North America. A behind C the same as B ahead of D 1 hour different from 20. What is the main cause of the earth's seasons? A the earth's tilt B the earth's tides C the moon's revolution around the earth D the gravity between the moon and earth 23. Antarctica is located in the ^_ Hemisphere. A Northern B Eastern C Western D Southern Critical Thinking Write the answer to each of the following questions. 24. How are latitude and longitude alike and different? 25. How would day and night be different if the earth did not rotate? Test-Taking Tip Answer all questions you are sure of first, then go back and answer the others. Describing the Earth Chapter 9 235

2 Chapter Minerals and Rocks Suppose you were hiking and found a gleaming chunk of rock. Would you think that you had struck gold? Or would you know that you had found pyrite, sometimes called "fool's gold"? Gold and pyrite are two types of minerals. Minerals combine in a variety of ways to form rocks. A large part of the earth is made of rock. Rocks form mountains, islands, valleys, cliffs, and even the ocean floor. The rocks you see around you are thousands of years old. They haven't always looked the same. They haven't always stayed in the same place. Rocks change. In Chapter 10, you will learn how minerals and rocks are formed. You will also find out how one type of rock can change over time into another rock type. Organize Your Thoughts Igneous Metamorphic Rock cycle Sedimentary 236 Goals for Learning To explain what a mineral is To identify basic properties of all minerals To compare minerals by their properties To explain what a rock is To describe igneous, sedimentary, and metamorphic rocks To explain how each rock type is formed To describe the rock cycle and the forces involved in it

3 Lesson Minerals Objectives After reading this lesson, you should be able to + explain what a mineral is. + name some common minerals. ^ identify four properties of minerals. + describe a streak test. Mineral Element or compound found in the earth The earth around you is a mixture of useful compounds and elements. Scientists classify some of these compounds and elements as minerals. Features of Minerals What do copper, quart/, and diamond have in common? They are all minerals. Elements or compounds are called minerals if they have these five features: + They are solids. + They arc formed naturally in the earth. ^ They have the same chemical makeup throughout. ^ They are not alive or made of living things. + They have definite arrangement of atoms. About 3,000 different minerals are found in the earth. Some are common, but most are rare. In fact, only a small number of minerals make up most of the earth's surface. The most common minerals are aluminum, quartz, feldspar, mica, calcite, dolomite, halite, and gypsum. Copper deposits often tarnish to a brown or green color. Some minerals, such as gold (Au) and sulfur (S), are pure elements. Graphite and diamond are different forms of pure carbon. Most minerals, however, are compounds. They are made of two or more kinds of elements. For example, quart/ (SiO.,) is made of the elements silicon (Si) and oxygen (O). and ('htipter

4 Luster How a mineral reflects light Properties Used to Identify Minerals Pyrite is sometimes called fool's gold because people can easily mistake it for gold. However, no two minerals share the same physical properties. For example, pyrite is almost the same color as gold, but it is harder than gold. In this lesson, you will learn about four properties used for identifying minerals. Color Some minerals have a unique color. For example, sulfur is usually bright yellow. However, most minerals can be found in more than one color. For example, quartz might be clear, purple, pink, black, or white. The color varies because the mineral is not usually found in a pure form. It often contains tiny amounts of different minerals called impurities. Many minerals are similar in color, such as pyrite and gold. Color is one clue to a mineral's identity, but color alone is usually not enough of a clue. Talc has a pearly luster. Luster Some minerals are shiny, but others look dull. Different minerals reflect light differently. The way that a mineral reflects light is called luster. There are two main kinds of luster: metallic and nonmetallic. Shiny minerals, such as gold and silver, have a metallic luster. Minerals with a nonmetallic luster can be described in several ways. For example, if a mineral looks like a pearl, its luster is described as pearly. A mineral that looks like glass is said to have a glassy luster. Compare the luster of the minerals shown here. Calcite has a glassy luster. 238 Unit 2 Earth Science

5 Streak Color of the mark a mineral makes on a white tile Hardness Ability of a mineral to resist being scratched Ancient miners discovered that the best places to dig for precious metals were the cracks and vents of volcanoes. They found copper, iron, silver, and gold by digging horizontal shafts near volcanoes. Streak When you rub a soft mineral across a tile, it leaves a mark. The color of the mark is the mineral's streak. A streak test helps you identify a mineral because all samples of the same kind of mineral make the same kind of streaks. The tile used in a streak test is called a streak plate. It is made of white, unglazed porcelain. The streak of a mineral maybe different from the mineral's color. For example, chunks of gold and pyrite are both gold colored, but you can tell them apart with a streak test. Gold has a yellow streak, but pyrite has a black streak. Some minerals are so hard, however, that they will not leave a streak. The table below gives the luster and streak of some minerals. Notice that quartz docs not leave a streak. Mineral gold silver pyrite quartz calcite talc hematite The Luster and Streak of Some Minerals Luster metallic metallic metallic glassy glassy pearly metallic or dull Streak yellow silver-white gray to black colorless white white red to brown Hardness Suppose someone offers to sell you a diamond ring. How can you tell if the diamond is real? You could do a simple test. You could see if the diamond can scratch a piece of glass. A diamond will scratch glass because it is harder than the glass. Diamond is the hardest of all minerals. It will scratch any other material. Rut nothing will scratch diamond. The hardness of a mineral describes how well the mineral resists being scratched. Geologists measure hardness on a scale of 1 to 10, called Mohs' scale of hardness. This scale is described in a table on the next page. Minerals and Rocks Chapter

6 Mohs' Scale of Hardness Some minerals are good for you. Calcium and phosphorus are necessary for strong bones. Your body needs iron to make red blood cells. Zinc helps your body to heal. These and other minerals are in the food you eat. Do you know what foods contain calcium? All minerals look about the same. Fact: Although all minerals have some characteristics in common, there are great differences among them. Some minerals are soft enough to scratch with your fingernail. Some minerals are hard enough to scratch glass. Mineral talc gypsum calcite fluorite apatite feldspar quartz topaz corundum diamond Hardness Quick Test scratched easily by fingernail scratched by fingernail barely scratched by copper penny scratched easily by steel scratched by steel scratches glass easily scratches both glass and steel easily scratches quartz no simple test no simple test The higher the number on Mohs1 scale, the harder the mineral. A mineral will scratch any other mineral that has a lower number. In the table, the mineral fluorite has a hardness of 4. It scratches calcite but does not scratch apatite. Feldspar will scratch calcite, fluorite, and apatite. You can use Mohs' scale to find the hardness of an unknown sample. Scratch the sample against each mineral on the scale, starting with the softest mineral. If the unknown sample scratches one mineral, test it with the next. Keep moving up the hardness scale, testing until the sample itself is scratched by one of the minerals. Its hardness is between that of the last two minerals tested. For example, a mineral that scratches feldspar but is scratched by quartz has a hardness of about 6.5. If you do not have a set of minerals, you can use the "quick test" instead. The quick test in the table above shows how to use common materials to test hardness. For example, suppose you cannot scratch a mineral with your fingernail but you can easily scratch it with a penny. The mineral probably has a hardness between 2 and 3. Geologists working in the field usually use the quick test. 240 Unit 2 Earth Science

7 Lesson 1 REVIEW Write your answers to these questions on a sheet of paper. 1. What are the five features of a mineral? 2. Name two common minerals. 3. How do you determine a mineral's streak? 4. The hardness of quartz is 7. The hardness of topaz is 8. Will quartz scratch topaz? Explain. 5. What is the hardness of a mineral that is scratched by steel but does not scratch glass? Is coal good or bad? Science in Your Life Coal is an organic sedimentary rock that forms from decaying plants and animals. Coal forms very slowly. In fact, it takes millions of years of heat and pressure to turn plant and animal remains into coal. The diagram below shows the stages of coal formation. Coal is a source of energy. People mine and burn coal to create electricity and to run plants such as steel mills. The energy content of anthracite and bituminous coal is the highest. Some countries, such as Poland, use lignite for energy. In the United States, only Texas and North Dakota use lignite. Sixty-four percent of the world's coal is used by China, the United States, India, Russia, and Germany. Most of the coal reserves in the world are found in Europe, Asia, Australia, and North America. Using coal has some disadvantages. First, there is a limited amount of coal in the earth. It won't last forever. Second, coal must be mined by digging deep in the earth or by stripping off a shallow layer of earth. This harms the earth's surface and can be dangerous for miners. Third, burning coal increases air pollution. Find out about other sources of energy that are less harmful in Appendix A. Minerals and Rocks Chapter

8 INVESTIGATION Observing Color, Streak, and Hardness labeled samples of minerals streak plate copper penny steel spoon Purpose How could you show that minerals have unique physical properties? In this investigation, you will describe the color, streak, and hardness of known mineral samples. Procedure 1. Copy the data table on a sheet of paper. Mineral Name Color Observations Streak Observations Quick Test Observations Hardness Estimate ^ - 2. Write the name of each mineral sample in the first column of the data table. 3. Observe the color of each sample. Record your observations in the data table. 4. Rub each sample across the streak plate, as shown here. Record your observations in the data table. 242 Unit 2 Earth Science

9 5. Refer to the Quick Test column of Moris' scale on page 240. Try to scratch each sample with your fingernail, the penny, and the spoon. Record your observations. Wash your hands and fingernails. 6. Using Mohs' scale and your observations from step 5, estimate the hardness number of each sample. 7. Return the samples and equipment. Questions and Conclusions 1. Which property was the easiest to observe? 2. Which property was the hardest to observe? 3. How did the color of each mineral compare to its streak? Explore Further Ask your teacher for an unknown mineral sample. Identify it by finding its hardness. Use the materials and minerals you already have. Explain how you tested the sample. Minerals and Rocks Chapter

10 Rocks and Rock Types Objectives After reading this lesson, you should be able to + explain what rocks are. + name three types of rocks. + describe how one type of rock can change into another type. + explain the forces involved in the rock cycle. About 3,000 minerals occur in the earth. Most of them are not found in a pure form. They are mixed together in rocks. A rock is a solid, natural material made of one or more minerals. Only about 20 minerals make up 95 percent of the earth's rocks. Geologists are interested in how rocks are formed and what minerals they contain. This information helps scientists and engineers locate valuable resources, such as oil and metals. Knowledge of rocks is necessary for undertaking construction projects and understanding the environment. Rocks also provide clues about the history of the earth and how the earth changes. Geologists classify, or group, rocks into three main types, depending on how they form. Some rock forms when hot, melted minerals cool and harden. This rock is igneous rock. Igneous rock can form above or below the earth's surface. Rock Natural, solid material macle of one or more minerals Igneous rock Rock formed from melted minerals that have cooled and hardened Basalt is on example of igneous rock. 244 Unit 2 Earth Science

11 Sedimentary rock Rock formed from pieces of other rock and remains of living things that have been pressed and cemented together Metamorphic rock Rock thai has been changed by intense heat, pressure, ami chemical reactions Another type of rock forms when bits of other rocks and the remains of living things are pressed and cemented together. The result is sedimentary rock. Sedimentary rock can form under a body of water or on the earth's surface. Sandstone is an example of sedimentary rock. Heat, pressure, and chemical reactions can change sedimentary or igneous rock into another type metamorphic rock. Metamorphic rock always forms below the earth's surface. This metamorphic rock shows the squeezing effect of heat and pressure deep in the earth. The photos show examples of the three rock types. What features do you notice about each one? In this lesson, you will learn more about how each type of rock forms. Huge blocks or slabs of marble are often needed as building materials. Because of this, explosives are not used to mine marble. Explosives would shatter marble into pieces that are much too small. Instead, special machines, called channeling machines, are used to mine marble. These machines cut holes in a "dotted line" across a marble rock. More "dotted lines" are cut until a large block shape is outlined. Then wedges are driven into the holes. The marble block is pried away from the surrounding marble and hauled to the surface. Minerals and Rocks Chapter

12 Rock cycle Series of natural changes that cause one type of rock to become another type of rock Magma Hot, liquid rock inside the earth Extrusive rock Igneous rock that forms from cooled lava on the earth's surface Intrusive rock Igneous rock that forms underground from cooled magma The Rock Cycle Rocks arc always changing. Some melt deep in the earth, then harden. Some are built by layers of sediment. Others twist and bend because of underground heat and pressure. Each type of rock igneous, sedimentary, and metamorphic can also change into another type. The series of changes that cause one type of rock to become another type of rock is called the rock cycle. This cycle occurs over a long period of time. Study the rock cycle diagram below. Each arrow is one possible pathway in the cycle. The label by each arrow tells you what force is causing the rock to change. Follow the arrows as we travel along the cycle, starting with magma. As magma rises from deep in the earth, it cools and hardens into igneous rock. Volcanoes quickly deposit lava on the earth's surface as extrusive rock. Pressure eventually lifts intrusive rock to the surface as well. Compacting and Burial, heat, and pressure Weathering and erosion Melting Cooling and hardening 246 Unit 2 Earth Science Once on the earth's surface, all rock types begin to slowly break apart into pebbles and then into fine grains like sand. They are easily carried away, often ending up in a large body of water.

13 Rocks and minerals are two words for the same thing. Fact: Rocks are made of minerals, but minerals are not made of rocks. Rocks are mixtures of one or more minerals. At the bottom of a lake or an ocean, sediment forms layers. Over time and under pressure, the layers compact and cement into sedimentary rock. Sometimes sedimentary rock is later brought to the earth's surface, where it begins to break down again. Other times, sedimentary rock becomes buried deeper in the earth. There the rock is exposed to heat and pressure. These underground forces can bend and twist it into metamorphk rock. In the same way, intrusive rock can become metamorphic rock. Sometimes metamorphic rock is brought to the surface, where it begins to break down again. In extreme underground heat, all three types of rock can melt. Most rocks melt at temperatures of 800 C or higher. Then they become magma deep in the earth, and the rock cycle continues. Rocks change by forces inside the earth and by forces on the earth's surface. Look again at the diagram. Below the earth's surface, forces of heat and pressure cause rocks to bend or melt. Above ground, forces such as wind and water cause rocks to break down, move, and settle. The Rock Cycle Theory Achievements in Science The idea of a rock cycle was first proposed in the 1 700s. At that time, geology as a formal science did not exist. Most people believed the earth was only about 6,000 years old. Many thought that only major disasters such as earthquakes could change the earth's surface. James Mutton was a Scottish physician and farmer. He loved to study science and ask questions. In particular, he wanted to find the origin of rocks and minerals. By studying rocks in Scotland, Mutton noticed streaks of granite among sedimentary rock. He thought this showed that there was heat, even fire, deep in the earth. He also found vertical layers of rock topped with horizontal layers. He concluded that the lower layers had to be very old. They must have been tipped on their side before the new layers were added. In 1 785, Hutton published his theory of rocks in a book. He proposed that one rock type changes into another over time. These changes are caused by pressure and heat deep in the earth. He also stated that erosion, weathering, moving of sediment, and the uprising of rocks from beneath the earth's surface are all part of a cycle. Hutton believed that this cycle has been repeating for millions of years, not for thousands of years. Because of his contributions, James Hutton is called the father of geology. Minerals and Rocks Chapter

14 Lesson 2 REVIEW Write your answers to these questions on a sheet of paper. 1. What is a rock? 2. What information about the earth can rocks provide? 3. What are the three main types of rocks? 4. Which type of rock is formed from melted minerals? 5. Name two underground forces that change rocks. AT-* AT-* AT-* AT-* AT-* AT-* AT-* Stonemason -* AT-* AT-* AT-* A V«AT-* AT-* A Science at Work Stonemasons build things out of stone. They build stone walls along shorelines and in landscapes. They lay tiles and paving stones for floors and patios. They cut and polish stone slabs for kitchen countertops and fireplaces. They fix old buildings and carve cemetery statues. They work with either natural stone, such as marble, granite, and limestone, or artificial stone, such as concrete. A stonemason begins a project by looking at or creating plan drawings. In these drawings, stones may be numbered so they are correctly cut and placed. The stonemason then selects, splits, cuts, and shapes the stones. Stones can be set in different ways. For a wall, stones are first set in a shallow bed of mortar, then aligned and leveled. The wall is built by alternately placing stones and mortar. Most stonemasons start out as apprentices. Apprentices observe and help experienced workers until the apprentices learn how to do the job alone. Vocational and technical schools also offer stonemason training. Stonemasons need to be highly skilled at handwork. They need to be precise and creative in solving visual problems. Strength and physical fitness are important because of the tools, machines, and heavy materials involved. Stonemasons should be comfortable working at heights and in noisy environments. 248 Unit 2 Earth Science

15 Chapter 10 SUMMARY A mineral is an element or a compound that occurs naturally, is a solid, is not alive or made of living things, has the same chemical makeup throughout, and has a definite arrangement of atoms. A mineral can be identified by its properties. These include color, luster, streak, and hardness. Minerals have either a metallic or nonmetallic luster. A mineral's streak is tested by rubbing the mineral across a streak plate. Mohs' scale of hardness ranks minerals according to how well they resist being scratched. A rock is a solid, natural material made of minerals. The three types of rocks are igneous, sedimentary, and metamorphic. Igneous rocks form from magma or lava that hardens. Sedimentary rocks form from particles called sediment. The layered sediment gets pressed and cemented into rock. Metamorphic rocks form from other rocks that are twisted and bent by heat and pressure. Rocks change from one type to another in the rock cycle. This cycle is driven by forces above and below the earth's surface. Science Words hardness, 239 extrusive rock, 246 igneous rock, 244 intrusive rock, 246 luster, 238 magma, 246 metamorphic rock, 245 mineral, 237 rock, 244 rock cycle, 246 sedimentary rock, 245 streak, 239 Minerals and Rocks Chapter

16 Chapter 10 R E V I E W Word Bank hardness igneous rock luster magma metamorphic rock mineral rock rock cycle sedimentary rock streak Vocabulary Review Choose the word or phrase from the Word Bank that best matches each phrase. Write the answer on your paper. 1. can be tested by scratching 2. solid element or compound that is found in the earth 3. color of the mark left on a tile 4. glassy, pearly, or metallic 5. Rocks change from one type to another in the. 6. Hot, liquid rock beneath the earth's surface is. 7. _ _ forms from rocks that have been changed by heat, pressure, and hot fluids. 8. Layers of sediment that are pressed together and cemented can form. 9. Liquid rock that cools on or below the surface forms 250 Unit 2 Earth Science 10. Natural, solid material made of one or more minerals is called. Concept Review Choose the word or phrase that best completes each sentence. Write the letter of the answer on your paper. 11. A rock is a mixture of. A animals B minerals C plants D bands 12. The three main types of rocks are. A clastic, extrusive, and intrusive B sedimentary, organic, and foliated C quart?,, feldspar, and mica D metamorphic, igneous, and sedimentary 13. Not all minerals are _. A solids C shiny B found in the earth D formed naturally

17 14. Mineral A is harder than mineral B if. A A weighs more than B B A scratches B C A leaves a bigger streak than B D A is more dense than B 15. Gold and pyrite are different in. A color B luster C feel D streak 16. Two kinds of luster are. A shiny and dull B metallic and nonmetallic C yellow and cube-shaped D silver and gold 17. You test for streak by _. A rubbing a mineral sample on a white tile B breaking a mineral sample C weighing a mineral sample in water D scratching a mineral with your fingernail 18. On Moris' scale of hardness, diamond has the A lowest hardness C darkest streak B brightest luster D highest number Critical Thinking Write the answer to each of the following questions. 19. Two unknown mineral samples are different colors. Their other properties are the same. What does this tell you? 20. The wall of a canyon is layered and seems to be made of sand cemented together. In one part of the wall, you see a pattern like the one shown. What rock type is it? How was the rock formed? Where did it form and why? When studying for a test, use a marker to highlight important facts and concepts in your notes. For a final review, read what you highlighted. Minerals and Rocks Chapter }0 251

18 Chapter Weathering and Erosion Materials on the earth's surface are constantly changing. Rocks and soil break down and move. Sometimes we notice these changes. But most of the time, they happen very gradually. It took millions of years for wind and running water to carve the Grand Canyon. Water and wind continue to shape the canyon today. In fact, water and wind constantly shape the land where you live too. In Chapter 11, you will learn about the processes of weathering and erosion. You also will learn about some landforms caused by erosion. Organize Your Thoughts Mechanical Weathering Chemical Water Erosion Gravity Glaciers Goals for Learning To explain weathering and soil formation To describe how water, glaciers, wind, and gravity cause eroson To give examples of several eroded landforms To describe how deposited landforms develop 252