Stress and Strain in the Life of a Rock By Patti Hutchison

Stress and Strain in the Life of a Rock By Patti Hutchison 1 The earth's surface is constantly changing. We don't usually see the changes because they happen so slowly. But earth's crust is always being pushed, pulled, folded, and broken. What causes these changes? Stress. 2 Earth's crust is made up of plates of rock. These plates move about on the asthenosphere. This is a mostly molten layer of the upper mantle. As they move about, the plates are pushed and pulled. This force is called stress. 3 Stress causes the rocks of the crust to slowly change. Their volumes change. Their shapes also change. Stress causes rocks to move up, down, or sideways. They tilt, fold, and even break. This is called deformation. 4 There are three main types of stress. One type is called compression. During compression rocks are pushed together. Think of how you used to squeeze mud in your hands. As you pushed the mud together, some oozed out the top and bottom of your hand. 5 Rocks are squeezed in the same way by stress. When this happens, rocks are pushed higher and deeper. A rock that was once flat will bulge in the middle as a result of compression. 6 Rocks can also be pulled apart by a type of stress called tension. Think of having a piece of clay in your hands. As you pull both ends, the clay stretches. It gets thinner in the middle. It stays thick on the ends. Tension can cause rocks to stretch in this same way. 7 There is a third kind of stress called shearing. This pushes rock in opposite, horizontal directions. The rocks bend and break. They can crack. The crack that forms is called a fault. Rocks on one side of a fault slide past the rocks on the other side. Earthquakes often occur along faults in the earth's surface. 8 Sometimes stress causes the rocks to bend instead of breaking. A bend in a rock is called a fold. An upward fold is called an anticline. A downward fold is called a syncline. Folds in the earth's crust can be so small you can't see them without a magnifying glass. Some are large enough to form mountains. 9 Why do some rocks fold, and others fault? Many factors affect these actions. One is temperature. Rocks that become very hot during compression usually fold. Higher pressure will also likely cause rocks to fold instead of fault. 10 Some rocks are brittle. They break easily under stress. Others are ductile. This means they bend easily. These rocks are more likely to fold. The way the force is applied to a rock will also determine whether it will fold or fault. If the force is applied quickly, the rock will usually fault. If it is applied slowly, it will likely fold. 11 Stress and strain take a toll on rocks. Pressure caused by the movement of plates changes the earth's crust. These changes usually happen over long periods of time. Just think: some of the mountains you see today were once flat land. The earth looks very different today than it did billions of years ago. Copyright 2012 edhelper

Name Date Stress and Strain in the Life of a Rock 1. What two things change as rocks undergo stress? 2. Rocks are pushed together during. Compression Shearing Tension 3. A crack that forms in a rock is called. A fault A fold Tension 5. Name two factors that determine whether rocks will fold or fault under stress. 4. A bend in a rock is called. A fold Shearing A fault 6. A brittle rock will likely. Fold Stretch Fault

Resources from the Land By Patti Hutchison 1 Caption: Dust storm approaching Stratford, Texas, April 18, 1935. 2 "Give me land, lots of land, under starry skies above. Don't fence me in." Have you ever heard that song? It describes a love for open spaces, mountains, and trees. Our land is an important natural resource. 3 Land provides a place for humans and animals to live. It also provides places to grow crops, trees, and grasslands. These are important resources for living things. What other natural resources do we get from the land? Let's start from the top. 4 At the surface of the land is topsoil. Topsoil contains minerals and nutrients that plants need to grow. Rich topsoil is used by farmers to produce food for us to eat. It can take up to 1000 years to form a few inches of topsoil. But those few inches can be lost in a matter of minutes. Without plant cover, topsoil can be eroded by wind or water very quickly. 5 Farmers need to be careful when plowing the land. Soil should not be left bare. The Earth loses much of its topsoil each year. It is eroded faster than it can be replaced. The result is drier and less fertile soil. In some areas, erosion is causing desertification. The land is drying up and becoming like a desert. Soil is needed to feed a growing population. Many areas have plans to help conserve the soil we depend on for so much. 6 Below the soil, the land contains sand and gravel. These resources can be used for many things. They provide us with concrete for roads and mortar for brick buildings. 7 Clay is another resource given to us by the land. It is found below the surface. Clay is used to make bricks, which are important building materials. Clay is also used to make ceramic tiles used for floors and walls. Beautiful pottery and china is made of clay as well. 8 A little deeper below the surface is bedrock. This is solid rock such as granite or marble. Many of these rocks can be cut from the earth in a quarry. This is a kind of rock "mine." These rocks are resources that can be used for buildings and statues. 9 Ores are mined deeper below the surface. These are important rocks that contain metals. These include iron and aluminum. These metals have to be removed from the rocks. These resources are also used for building and manufacturing. 10 Sodium chloride, also known as salt, is found both underground and on the surface. Another mineral resource found on the land is gypsum. This material is used to make plaster, a useful building material. Graphite, a lubricant, and talc, which is used in cosmetics, are two more resources provided by the land. 11 Of course, the land is also an important resource for recreation. Many thousands of acres have been set aside and protected. These forests, parks, and wildlife refuges are places of pleasure for many of us. We need to respect the land so that it keeps on giving us the natural resources we need. Copyright 2012 edhelper

Name Date Resources from the Land 1. What does topsoil give to plants? 2. How long does it take to make a few inches of topsoil? 10 years 1000 years 100 years 3. Name one type of building material that is made from sand and gravel. 4. A rock "mine" is called: A quarry Bedrock An ore 5. Rocks that contain important metals are called: Topsoil Mines Ores 6. Name two resources found in or on the land.

Minerals By Patti Hutchison 1 Minerals. They are all around us. We eat them, wear them, and build with them. What is a mineral? How are they identified? What can we do with them? 2 Earth's crust is made of about three thousand minerals. Only about thirty of them are common to us. A mineral is a solid with certain properties. First, it must occur in nature. Minerals are "found," not made by humans. 3 Second, a mineral is inorganic. This means that it has never been living. 4 Another characteristic of a mineral is that it has a definite set of elements that make it up. It must also have the structure of a crystal. 5 A crystal is a solid. Its atoms are arranged in repeating patterns. Snowflakes are a type of crystal. You may also have seen ice crystals form on the grass when there is a frost. These are examples of what crystals look like. They are also examples of minerals. 6 There are two major ways minerals are formed. Some are formed from magma. You know that magma is liquid rock far below the Earth's surface. Sometimes magma is forced up into the cooler layers of the Earth. The elements in the magma form crystals when they cool. If magma cools quickly, the crystals in the mineral will be small. If it cools slowly, the crystals will be large. 7 Minerals also form from solutions. A solution can become saturated. It can't hold any more of whatever is dissolved in it. Elements begin to "fall out" of it. These elements form minerals. Sometimes, the liquid in the solution is evaporated. Minerals are left behind. 8 Minerals are sorted into groups. One group is called silicates. They are made of oxygen and silicon. These are the two most common elements in the Earth's crust. Feldspar and quartz are the two most common minerals. They are examples of silicates. 9 Carbonates are another class of minerals. They are made of metallic (shiny) elements. These are combined with carbon and oxygen. These minerals often form rocks such as limestone and marble. 10 Another group of minerals is called oxides. Oxides form from oxygen and a metal. These are good minerals to build things from. 11 There are several tests scientists use to identify minerals. Different qualities of a mineral help us to know exactly what kind it is. One test is color. You can see the color of a mineral just by looking at it. A mineral's color helps us know what elements are in it. 12 Another test used is luster. If a light bounces off the surface of a mineral, it has luster. Luster can be either metallic or nonmetallic. Minerals sometimes contain gold, copper, or silver. These metals make a metallic luster. Minerals with nonmetallic luster are duller. Calcite and quartz have nonmetallic luster. 13 Luster and color are usually combined with a test of a mineral's texture. Texture describes how the mineral feels. It might be smooth or rough. It might feel soapy or glassy. 14 When a mineral is rubbed across a special surface, it might leave a streak. This is like drawing with chalk on

a chalkboard. Streak is the color a mineral leaves behind when it is drawn across the surface. A mineral's streak doesn't change much, no matter what happens to it. Streak is a good test to help identify a mineral. 15 Scientists also test minerals for hardness. Hardness is a measure of how easily a mineral can be scratched. Scientists use the Mohs scale of hardness to identify a mineral. Harder minerals will scratch softer ones. Talc is a very soft mineral. It is number one on the Mohs scale. Diamonds are very hard. They are number 10 on the scale. 16 Another test used to identify a mineral is cleavage. The mineral is broken. If it breaks evenly along a smooth line, it is said to have cleavage. If a mineral doesn't have cleavage, it will break in a ragged line. These minerals are said to have fracture. 17 Minerals are all around us. People build buildings and roads from minerals. There are special minerals called gems. These are used for jewelry. If you take a vitamin in the morning, you are putting minerals in your body. Cereals and other foods also contain minerals. Minerals are very useful in our daily lives. Copyright 2012 edhelper Name Date Minerals 1. Name two properties of a mineral. 2. What are the two ways minerals are formed? 3. Silicates contain: Gold and carbon Iron and talc Silicon and oxygen 5. If light bounces off a mineral, it has: Luster Hardness Color 4. Minerals formed from oxygen and a metal are called: Oxides Silicates Carbonates 6. If a mineral breaks along a smooth line, it has: Fracture Hardness Cleavage

Igneous Rocks - Don't Just Take Them for Granite By Patti Hutchison 1 Igneous means "formed from fire." Igneous rocks are formed from fiery magma. This is hot, liquid rock deep inside the earth. When it comes close to the surface, it cools into hard rock. 2 How is magma formed? As you go farther below the surface of the earth, temperature and pressure increase. Rocks and minerals melt under these conditions. They combine with gases in a kind of rock soup. As this mixture cools, it forms crystals. 3 If the magma breaks through the surface, it becomes lava. It cools very quickly. Extrusive igneous rocks form. The crystals are very small. These rocks have a fine grain quality to them. 4 If the magma stays below the surface, it cools slowly. Coarse-grained igneous rocks are formed. The crystals are very large. These are called intrusive igneous rocks. 5 Igneous rocks are classified by scientists according to certain characteristics. One way they are classified is by the minerals that make them up. 6 Felsic rocks are light colored. They contain a lot of silica. Silica is the most common mineral in the earth's crust. Obsidian is an example of a felsic rock that is extrusive. It is a shiny rock that looks like black glass. Granite is a common felsic rock that is intrusive. 7 Another classification of igneous rocks is called mafic. Mafic rocks are dark-colored. They contain a lot of iron. Basalt is an extrusive mafic rock. Gabbro is an intrusive mafic rock. 8 Igneous rocks are used in many ways. Lava that cools with air bubbles in it forms a rock called pumice. Pumice is very light weight. It is used as a cleaning tool. 9 Another useful igneous rock is granite. Granite is a very hard rock. It comes in many colors. It can be gray, pink, white, or red. It is used to make buildings. Many tall buildings in cities are made of granite. 10 Sometimes gems are formed under the pressure and cooling of magma. They are found in igneous rocks. Diamonds and other gems are crystals that are made into jewelry. 11 Igneous rocks are formed in a continuous cycle. Rocks and minerals melt deep beneath the earth. They form magma. Magma bubbles up closer to the earth's surface. It cools and forms igneous rocks, which we can use in many ways. Copyright 2012 edhelper

Name Date Igneous Rocks - Don't Just Take Them for Granite 1. Igneous rocks are formed from. Magma Lava Both A and B 3. Intrusive rocks have. Fine grains Large crystals Small crystals 2. Extrusive rocks cooled. Over thousands of years Quickly Slowly 4. Dark colored rocks that contain a lot of iron are classified as. Felsic Mafic Gems 5. How is magma formed? 6. Explain how igneous rocks are formed.

Sedimentary Rocks By Patti Hutchison 1 If you put some muddy water in a jar and let it set a few days, what would you see? The water would become clear. There would be layers of dirt and stones at the bottom. This is called sediment. This is what sedimentary rocks are made from. 2 The sediments are pieces of rock. They have been broken apart by weathering. Wind, water, and ice break down rocks and minerals into smaller particles. These pieces come together in different ways to form sedimentary rocks. 3 Running water, such as streams and rivers, helps form sedimentary rocks. The water carries the broken pieces of rock. Then it drops them in layers wherever the current slows down. This is called deposition. 4 After the layers are deposited, sedimentary rocks begin to form. This can happen in one of three ways. They can be formed by a process called compaction. Layers of sediment are squeezed together. The pressure of the rocks on top causes this to happen. 5 Sedimentary rocks can also be formed by cementation. This happens when water evaporates out of the layers of sediment. Minerals are left behind. They "glue" the pieces of rock together. 6 Cementation is kind of like building a brick wall. The bricklayer puts a mixture of sand and water between the bricks. This layer hardens as it dries, and the bricks stick together. Sedimentary rocks are formed almost the same way. The minerals between the rocks dry and stick the pieces together. 7 The third way sedimentary rocks are formed is by recrystallization. Minerals that dissolved in the water fall out. New mineral grains are formed. They are bigger than the original grains. The crystals form together into a solid rock. 8 There are three kinds of sedimentary rocks. Clastic rocks are made from pieces of other rocks. They are formed by compaction and cementation. Clastic rocks can range in size from tiny particles of soil to huge boulders. Shale and sandstone are two common clastic rocks. 9 Non-clastic sedimentary rocks are formed when minerals separate from ocean water. The minerals mix with sediments on the ocean floor. They recrystallize into solid rocks. Chalk is a common non-clastic rock. 10 The third kind of sedimentary rock is called organic. These form from decayed plants and animals. They are usually formed in oceans or swamps. The decayed material is compacted into rock. Two common organic rocks are limestone and coal. 11 Sedimentary rocks give us important resources. Most ground water is found in sedimentary rocks. Coal, oil, and natural gas are found in these rocks. These are important energy resources. 12 Sedimentary rocks also give us building materials. Iron is used for making steel. Limestone is made into cement. It is also cut to make blocks for large buildings. Where would we be without sedimentary rocks? Copyright 2012 edhelper

Name Date 1. Dirt and stones at the bottom of a body of water are called. Clastic Crystals Sediments Sedimentary Rocks 2. The breaking up of rocks by wind, water, and ice is called. Cementation Recrystallization Weathering 3. What is deposition? 4. When layers of sediment are squeezed together to form rocks, it is called. Compaction Cementation Re-crystallization 5. When water evaporates and the minerals "glue" the rocks together, sedimentary rocks are formed by. Cementation Recrystallization Compaction 6. Name the three kinds of sedimentary rocks.

Metamorphic Rocks By Patti Hutchison 1 Metamorphosis. Where have you heard that word before? You may remember that insects go through metamorphosis. They change as they go through their life cycle. Metamorphosis means change. Metamorphic rocks are rocks that have changed in some way. 2 Metamorphic rocks start out as either sedimentary or igneous rocks. They become buried deep below the earth's surface. Most rocks melt. But some don't. Some rocks stay solid but change form. 3 What causes metamorphic rocks to form? The answer is heat and pressure. Heat can come from being buried deep below the surface. Or it can come from a nearby pool of magma. This is called contact metamorphism. 4 Pressure can happen in two different ways. It can be caused by the weight of other rocks on top. Rocks can be buried during mountain building. This is called regional metamorphism. Pressure can also come from movement of large areas of rock, called faulting. When this happens, dynamic metamorphism occurs. 5 What changes do heat and pressure cause? They can cause a rock to change texture. The mineral content might change. The chemicals in a rock can also change. The result is a new kind of rock. It takes many years for this to happen. 6 Metamorphic rocks can be recognized by the way they look. They are mostly layered in sheets. They are shiny. This is because their grains are lined up. Sometimes there are bands of different colors. 7 There are two common metamorphic rocks you probably know. Slate is one. Slate is formed when shale is exposed to extreme pressure. Slate is smooth and black. It was used at one time for blackboards and roof tiles. 8 Marble is another common metamorphic rock. Marble is made from limestone under high heat and pressure. It is a very hard rock with streaks of different colors running through it. Marble is used for carving beautiful statues. 9 The earth is constantly changing. Rocks below the earth's surface are changing, too. Think of metamorphic rocks as rocks that have been "recycled." Plastic soda bottles are melted down and made into something else. Igneous and sedimentary rocks are also reformed into metamorphic rocks. Copyright 2012 edhelper

Name Date Metamorphic Rocks 1. Metamorphic rocks start out as igneous or sedimentary rocks. False True 2. What causes metamorphic rocks to form? 3. What are the three types of metamorphism? 4. Metamorphic rocks are formed in a short amount of time. False True 5. What is slate formed from? Clay Coal Shale 6. What is marble formed from? Limestone Granite Obsidian

Answer Keys Stress and Strain in the Life of a Rock - Answer Key 1 Shape and volume 2 Compression 3 A fault 4 A fold 5 temperature, pressure, whether they are brittle or ductile, how quickly the force is applied (any two) 6 Fault Resources from the Land - Answer Key 1 nutrients and minerals plants need to grow 2 1000 years 3 concrete, mortar (any one) 4 A quarry 5 Ores 6 ores, salt, gypsum, etc. (any reasonable answer) Minerals - Answer Key 1 Naturally occurring, inorganic, crystal structure (any two) 2 From magma, from a solution 3 Silicon and oxygen 4 Oxides 5 Luster 6 Cleavage Igneous Rocks - Don't Just Take Them for Granite - Answer Key 1 Both A and B 2 Quickly 3 Large crystals 4 Mafic 5 Rocks and minerals melt under the heat and pressure below the earth's surface. 6 Magma cools and forms crystals. Sedimentary Rocks - Answer Key 1 Sediments 2 Weathering 3 When a river or stream drops rocks and dirt where the current slows. 4 Compaction 5 Cementation 6 Clastic, non-clastic, and organic Metamorphic Rocks - Answer Key 1 True 2 Heat and pressure 3 Dynamic, contact, and regional 4 False 5 Shale 6 Limestone