Rocks, Minerals, and Erosion Do not duplicate without permission from Orange County Department of Education
4 th Grade Earth Science Standards 4. The properties of rocks and minerals reflect the processes that formed them. As a basis for understanding this concept: 4a. Students know how to differentiate among igneous, sedimentary, and metamorphic rocks by referring to their properties and methods of formation. (The Rock Cycle) 4b. Students know how to identify common rock-forming minerals (including quartz, calcite, feldspar, mica and hornblende) and ore minerals by using a table of diagnostic properties. 5. Waves, wind, water, and ice shape and reshape earth s land surface. As a basis for understanding this concept: 5a. Students know some changes in the earth are due to slow processes, such as erosion, and some changes are due to rapid processes such as landslides, volcanic eruptions, and earthquakes. 5b. Students know natural processes, including freezing, thawing and the growth of roots can cause rocks to break down into smaller pieces. 5c. Students know moving water erodes landforms, reshaping the land by taking it away from some places and depositing it as pebbles, sand, silt, and mud in other places (weathering, transport, and deposition). Do not duplicate without permission from Orange County Department of Education. 2
Hi! I m Rocky and I m here to guide you through your study of: ROCKS, MINERALS AND EROSION. Let s start by learning a little about what the Earth looks like inside! What are the parts of the Earth? Let s take a look at the inside of the earth to see HOW and WHERE minerals and rocks are formed. The earth is not a solid ball of rock, but rather has four different layers: the crust, mantle, outer core and inner core. The crust is the outer layer of the earth on which we live. It is made of solid rock consisting mostly of granite, basalt, and gabbro. The crust includes all the rock types: sedimentary, igneous, and metamorphic. It rests on top of the mantle and varies in thickness from 6 miles thick under the oceans to approximately 40 miles thick at the mountaintops. The mantle lies just under the crust and is the earth s thickest layer, about 1,750 miles deep. The upper part of this layer is usually solid rock. However, because it is about 8,000 degrees Fahrenheit ( F), the lower part of the Mantle is soft, like melted plastic and is constantly slowly moving. Chunks of the earth s crust are called plates and rest on the moving mantle. The movement of the plates can cause earthquakes and weak areas or faults in the crust, allowing the magma to break through creating volcanoes. The outer core is a liquid rock material made of molten or melted iron, nickel, silicon, and carbon. It is about 11,000 F. Electrical currents coming from this area produce the earth s magnetic field. The inner core is a solid mass of iron and nickel that is around 13,000 F, which is close to the same temperature as on the surface of the Sun. The extreme temperature and pressure from the mass of the earth pushing on the core prevents the iron and nickel from melting. Do not duplicate without permission from Orange County Department of Education. 3
Hi! Have you ever wondered how diamonds are formed? Why all quartz crystals have the same shape? Have you ever wanted to go on a field trip to hunt for diamonds or emeralds? For hundreds of years, people have asked the same questions and searched for nature s beautiful minerals on the surface of the land or buried in the earth s crust. Today, geologists and mineralogists have discovered over 3,000 minerals on the earth. Over 100 of these minerals are so beautiful and rare that they are called gemstones. Some of the most valuable minerals are diamonds, emeralds and rubies because they are so rare and hard to find. Let s begin our search for information about minerals and rocks by finding out what minerals are and how they can be identified. What are Minerals? http://www.mii.org/helpforstudents.html www.min.uni-bremen.de/kabinett/klasse_1.en.html www.si.edu/ www.minerals.si.edu/images/gallery/mineral.htm A mineral is made of one or more elements (atoms), has a definite chemical formula and a definite crystal shape. For example, the mineral quartz is made of the elements Silicon and Oxygen. Its chemical formula is Si0 2, and its crystal shape always has 6 sides. Minerals are usually made from materials that were: *never living *formed in nature *not made in a laboratory Some minerals are formed in caves. Take a look at minerals being formed in caves at: www.goodearthgraphics.com/ How are minerals identified? To see pictures of minerals, visit: http://www.ivyhall.district96.k12.il.us/4th/kkhp/rocksandminerals/minerals.html Minerals are identified by the following properties or characteristics: hardness, luster, color, streak, and cleavage. Scientists have made charts of information about the hardness, luster, color, streak and cleavage of common minerals and use that information to help identify a mineral. Visit: Mohs Hardness Scale website: http://www.galleries.com/minerals/hardness.htm Do not duplicate without permission from Orange County Department of Education. 4
Let s take a look at each of the following properties or characteristics of minerals to see how Geologists or Mineralogists identify the name of a mineral. A. Hardness: Hardness is a measure of how easily a mineral may scratch or be scratched by another mineral. Harder minerals scratch softer minerals Visit: http://www.galleries.com/minerals/hardness.htm I can scratch you, so I am a harder mineral than you. That s ok! I m shinier than you! Scientists use the Mohs Hardness Scale to help find the hardness of a mineral because many minerals can look alike but have different levels of hardness. By using the Mohs Hardness scale, scientists can gather information about one of the mineral s properties to help identify it. The scale was developed by a German mineralogist, Friedrich Mohs, in 1822, to help find the hardness of a mineral by comparing it to 10 common minerals that represent 10 different levels of hardness. He placed these minerals on a scale of hardness from #1 to #10, with #1-the mineral, Talc, being the softest and #10, a Diamond, the hardest. Below is the Mohs Hardness Scale with the typical minerals that represent each level of hardness: Mohs Hardness Scale: Mineral: Hardness: Example: Talc 1 Gypsum 2 Use this scale to answer these questions: 2.5 fingernail Calcite 3 3.0 copper penny 1. Which mineral(s) can be scratched by a penny? Fluorite 4 Apatite 5 Feldspar 6 Quartz 7 Topaz 8 Corundum 9 Diamond 10 5.5 glass 6.5 steel file _ 2. What minerals(s) can be scratched by glass but not by a copper penny? _ 3. Which mineral(s) can scratch glass but not scratch a steel file? 4. True or False: The softest minerals are found at the top of this Mohs Hardness Scale. Do not duplicate without permission from Orange County Department of Education. 5
B. Luster: The luster of a mineral describes the way the surface of a mineral reflects light. If the surface looks shiny, then the mineral has a metallic or metal-like luster. If not shiny, then it has a non-metallic luster. If sparkling, then it has a brilliant luster. Visit: http://www.galleries.com/minerals/luster.htm I have a metallic luster because I reflect a lot of light off my shiny surface. C. Streak: The streak of the mineral is the color of powder left behind when the mineral is scratched onto another mineral or on a piece of unglazed tile or a streak plate. The color of a mineral s powder is just another clue to a mineral s identity. The color of a mineral s powdered streak is not always the same color as the mineral itself. For example, iron pyrite looks like gold and has a shiny gold color, but it leaves a black powder streak. Some minerals may even streak white or leave no powder at all if they are harder than the streak plate or another mineral. Visit: http://www.galleries.com/minerals/streak.htm I look like gold, but I leave a black powder streak. D. Cleavage: Cleavage is the tendency for some minerals to split easily along flat surfaces when they are broken apart. Another way to identify a mineral is by looking at its cleavage or the number and placement of the flat surfaces on a mineral. For example, mica has only one flat surface, so it can peel apart in layers. Salt or halite has 3 flat surfaces, like a cube. Whenever a mineral is broken into smaller pieces, each piece always has the same cleavage or number of flat surfaces as did the larger mineral. Visit: http://www.galleries.com/minerals/cleavage.htm E. Color: The color of a mineral cannot always be used to identify it because impurities from the surrounding area can be mixed with the mineral when it is forming and can turn the mineral different colors. For example, the mineral quartz can be found in many different colors, such as: smoky quartz, which can be yellow or brown, amethyst quartz can have various shades of purple, and milky quartz is cloudy or milky white. Visit: http://www.galleries.com/minerals/color.htm Do not duplicate without permission from Orange County Department of Education. 6
Mineral Hardness Luster Streak Color Other Calcite 3 nonmetallic white Feldspar 6 nonmetallic none colorless, white colorless, beige, pink Galena 2.5 3 metallic gray lead-gray Gold 2.5 3 metallic golden yellow yellow bubbles when acid is placed on it heavy for its size used for jewelry Graphite 1 2 metallic black gray to black feels greasy Mineral Identification Chart Hi! Look at the chart and answer the questions below: 1. What do you notice about the relationship between the luster and the color of the streak of a mineral? Hematite 5 6.5 metallic or nonmetallic Hornblende 5 6 nonmetallic none reddish brown silver-gray or red dark green to black 2. What have you noticed about the relationship between the luster and the color of the mineral? Magnetite 6 metallic black black magnetic Mica 2 2.5 nonmetallic none Pyrite 6 6.5 metallic greenish black Quartz 7 nonmetallic none Talc 1 nonmetallic white Copyright 2003 California Department of Education dark brown, black, or silver-white brassy yellow colorless, white, rose, smoky, purple, brown white, greenish to gray flakes when peeled called fool s gold feels greasy 3. Which minerals would be easily identified by using the texture of the mineral to identify it? 4. Which mineral on the chart has a property that is different from every other mineral on the chart? Do not duplicate without permission from Orange County Department of Education. 7
Hematite What is an ore? http://www.gwydir.demon.co.uk/jo/minerals/metals.htm An ore is a mineral or rock from which a metal can be removed. The biggest source of iron comes from the ore and hematite, which is made of iron and oxygen. Metals, like copper and aluminum, can be removed from various ores in a variety of ways. Some ores are crushed and then melted, allowing the metals in the rock material to float to the top to be skimmed off and removed from the other rock material. The melted metal material is then cooled and made into sheets of metal, wire, or molded into everyday objects. I m an ore called Hematite. I m reddish brown and have a lot of the metal iron in me. They use my iron to make steel and brass. How are minerals used in everyday life? Silver and copper can be used to make musical instruments, electric wire and jewelry. Gypsum can be used to make plaster and wallboard. Graphite is used in pencils and halite, or table salt, can be used to flavor and preserve food. Some minerals like copper must be refined and processed to make pennies, cookware, irrigation pipes and wire. Visit these websites and see how minerals and rocks are used in our everyday lives: www.amnh.org/nationalcenter/kids/kids_hope/rocksincab.html#backtome http://www.mii.org/periodic/lifeelement.html What is the difference between a rock and a mineral? www.arlington.k12.ma.us/rocksandminerals/default.html A mineral is made of one or more elements (atoms) that have a definite chemical formula and crystal shape. Rocks, however, are made of one or more minerals that were in the melted magma when the rock was cooled and formed. Rocks are made of different types of minerals and can be classified or grouped by how and where they were formed. For example, the igneous rock, granite, is made of three different minerals: quartz, feldspar, and mica or hornblende. It was formed deep in the Earth s crust where it cooled from melted rock material called, magma. We ll find out more about rocks in the next section! More information about minerals can be found on this website. Try answering the questions on this website! Good Luck! http://www.ivyhall.district96.k12.il.us/4th/kkhp/rocksandminerals/rocks.html Do not duplicate without permission from Orange County Department of Education. 8
Properties of Sedimentary, Igneous and Metamorphic Rocks Hi again! Now that we have learned that rocks are made up of minerals, we are ready to learn a little more about the properties of each type of rock and HOW and WHERE they are formed. Rocks can be classified into three major types: sedimentary, igneous and metamorphic. Let s find out some of the properties or characteristics of each type of rock. Sedimentary rocks, or settled rocks, are formed at or near the earth s surface and are weathered and broken apart (eroded) by wind, rain, or ice and deposited as sediments in rivers, lakes and oceans. Over time the sediments are cemented together through a chemical process called lithification. Igneous rocks or fire rocks are formed above and below the earth s surface. Magma, which is melted rock material, can cool below the earth s surface or erupt through volcanoes and then cool on the earth s surface. Metamorphic rocks - to change form are buried deep in the earth s crust and are heated up or baked, but not melted, from the heat and pressure in the mantle. Once heated, the rocks re-organize their atoms, cool, and re-crystallize into hard, dense rocks. Now let s look at the properties or characteristics of the different types of rocks: Sedimentary rocks: soft = made of sediments may have layers sandy or grainy texture smell like wet mud/cement bits and pieces of old rocks cemented together can contain fossils of once living plants and animals Igneous rocks: cooled from melted magma hard and no layers may have interlocking crystals may have small holes, rough texture fine textures or glassy = cooled quickly large, visible crystals = cooled slowly Metamorphic rocks: hard and dense minerals lined up in uneven layers atoms changed chemically Granite Sandstone Do not duplicate without permission from Orange County Department of Education. 9 Pumice
The Rock Cycle Hi again! Now that we have learned a little about minerals, we are ready to learn about rocks that make up the crust of the earth. First, it is important to remember that rocks are made from minerals, and that there are three different types of rocks: sedimentary, metamorphic and igneous. Rocks are classified into one of three types of rocks by HOW and WHERE they were formed. http://www.bbc.co.uk/education/rocks/rockcycle.shtml The picture of the Rock Cycle on the next page was designed by scientists to show how each type of rock can become another type over time, depending on what happens to them and where they are located. You will notice that the three types of rocks are located in the circular shapes, and that the arrows list the processes or ways one rock type can be changed into another. For example, Rocks may be: uplifted to the surface of the earth and become weathered or eroded away by rain, snow, wind, and ice. (1a and 3a) buried deep in the earth s crust over time, layer after layer. (2a-2b) heated or partially melted and then cooled, compressed, hardend and crystallized. (1b) completely melted and become part of the melted rock material called magma which is located in the mantle of the earth. (3b) Follow the numbers on the Rock Cycle picture as you read the following: Note: There is no special order that the rocks go through to change from one type to another. 1. Igneous rocks comes from the Latin word, ignis (ignite) or fire" because they are formed from hot, melted rock material called Magma that is located in the mantle, just under the earth s crust. Visit: http://www.ivyhall.district96.k12.il.us/4th/kkhp/rocksandminerals/igneous.html a. Igneous rocks may be uplifted by the heat and pressure from inside the earth onto the surface (1b) and then become eroded into small bits and pieces of rock material forming Sedimentary rocks (2). b. Igneous rocks may also be heated and become partially melted, cooled and crystallize into metamorphic rocks (3). 2. Sedimentary rocks means settled rocks. Sedimentary rocks are formed from rocks on the surface of the land that have been weathered and eroded or broken apart by wind, rain, waves, ice and glaciers. The rocks on the surface may be old metamorphic, igneous or sedimentary rocks that were uplifted to the surface. (1a & 3a). Over time, the rocks become buried, layer after layer, deep into the Earth s crust (2a & 2b). http://www.ivyhall.district96.k12.il.us/4th/kkhp/rocksandminerals/sedimentary.html 3. Metamorphic = meta means changed : morphic = shape or form. Metamorphic rocks are located deep in the mantle and have undergone a change, due to the heat and pressure that radiates from the earth's core (1b). The existing rocks are heated, just short of melting, and rearranged and re-crystallized forming rocks that are hard and dense. (1b) If the rock material is completely melted, it may harden into igneous rocks or become part of the magma in the mantle (3b). http://www.ivyhall.district96.k12.il.us/4th/kkhp/rocksandminerals/metamorphic.html Do not duplicate without permission from Orange County Department of Education. 10
Do not duplicate without permission from Orange County Department of Education. 11
The Rock Cycle Story Hi! I m back to tell you how I changed into all three types of rocks in the Rock Cycle over time. As you read the story below, whenever you see a number, stop and find the same number in the picture on the next page. It will help you follow me through the Rock Cycle as I became each type of rock over time. Color my happy rock face as you find it in the picture. I ll begin my journey in the earth s mantle, as part of the melted rock material called, magma #1 (find me). I had been part of the melted magma for thousands of years, moving slowing through the mantle. Suddenly, heat and pressure began to move into my area and push the magma upward through a large crack in the earth s crust. Some of my melted rock material didn t make it to the surface at that time, and it cooled and crystallized under the earth s surface, forming an igneous type of rock called granite. The word igneous comes from Latin word, ignis (ignite), as in fire because igneous rocks are formed from hot, melted rock material #2 (find me). Years later, heat and pressure from the earth s core began to move into my area and melt my granite layer, combining it with the rest of the melted rock material called magma. All of a sudden, the entire mass of magma was zooming up to the surface through a weakness in the earth s crust called a fault. How exciting! I was on my way to the top! FINALLY! W-H-E-E! WHAT A RIDE! Out of the top of a volcano I came, at 2000 F! Once magma reaches the surface of the earth, it is no longer called magma but rather lava. As soon as the lava hit the surface, it began to flow down the side of the volcanic mountain, cooled and hardened into a basalt type of rock, which is the most common igneous rock found on earth #3 (find me). Layer after layer, the melted, basalt rock material flowed down the side of the volcano, cooled and hardened in place. Over time, my basalt rock was weathered and eroded (broken apart) by wind, rain and ice. Water filled the cracks in my rock, froze and then expanded, causing me to break apart into smaller chunks and pieces #4 (find me). Rain, wind and moving water continued to tumble and break me into even smaller bits and pieces of rock and sand particles called sediments. Eventually, the sediments settled to the bottom of riverbeds, lakes and streams and some of us end up as pebbles and grains of sand on the beach #5 (find me). Over time, these sediments, and small rock particles harden and become cemented together with mud and sand, in a chemical reaction process called lithification, forming sedimentary rocks. I became part of a sedimentary rock called a conglomerate, which is made up of bits and pieces of different rocks and sand. The word sedimentary, means settled, meaning the rock pieces settled out in layers, usually under water #6 (find me). Thousands of years go by, and my sedimentary layers become buried deep in the earth s crust. Heat and pressure begin to move into our area and heated up, but did not melt the sedimentary rocks. When the rocks are heated, it causes the atoms in the rocks to re-arrange and re-crystallize into a new type of rock called a metamorphic rock. The word metamorphic means changed form, and in my case, my sedimentary conglomerate rock, changed or re-formed into a metamorphic rock called gneiss (nice) rock, now isn t that nice #8 (color ME in the gneiss)! Sometimes, magma from the mantle can move into an area of existing Metamorphic, Igneous or buried Sedimentary rocks and melt them completely until they become part of magma again. In time, the magma may cool underground or find its way up to the surface through a weakness in the earth s crust, and the cycle begins all over again #9-(find and color ME in the magma). Do not duplicate without permission from Orange County Department of Education. 12
The Rock Cycle Do not duplicate without permission from Orange County Department of Education. 13
How does an Igneous Rock become a Sedimentary Rock? Let me tell you what happened to me! Well, there I was, under the earth s surface, as part of a huge granite formation, when little by little, I realized that my entire formation was being uplifted to the surface. Of course, this didn t happen overnight but rather over thousands and thousands of years, an inch at a time! Finally, our entire formation was uplifted by heat and pressure from the mantle to the surface and WOW! What a change! Blue sky! Fresh air! Little by little, the entire formation was uplifted even further, creating a huge mountain range above the ground. Now that we were on the surface of the land, wind, rain, and ice slowly began to weather and erode away at our surface. Water got into the cracks in my rock and froze into ice. We all know what happens when water freezes --- it EXPANDS! The frozen ice makes the cracks become LARGER and DEEPER. Later, the ice melted and the water started to flow, pushing and shoving the small, broken chunks of rock material down a nearby stream and then onto a fast moving river. Down the river the small chunks of rock tumbled over and over, breaking into smaller and smaller pieces as they went. The rough edges became smooth and rounded and some pieces were deposited along the way in riverbeds and lakes. Others continued to tumble down the river for many, many years, finally making their way to the ocean as small grains of sand on the seashore. Over time, layers of sediments become cemented together chemically, in a process called lithification, forming many different types of sedimentary rocks. I became a sedimentary rock called sandstone, which was made of small pieces of sand cemented together. Here s what I looked like- I m a SANDSTONE rock Here is a picture of some other common types of sedimentary rocks. We are all made from bits and pieces of other types of rocks that have been weathered and eroded over time. SHALE: (hard mud) LIMESTONE:(I have fossils, too!) CONGLOMERATE (Small pieces of rocks and sand cemented together) Do not duplicate without permission from Orange County Department of Education. 14
How can a Sedimentary Rock become a Metamorphic Rock? Well, let me continue my story.... Over time, I was no longer sandstone on the surface of the earth, but became buried deep within the earth s crust as each layer of new sedimentary rock covered me up. Heat and pressure, from the hot, melted rock material in the mantle, begin to move into the area where I was located---heating, squeezing and compressing, but not quite melting the old sedimentary rocks in the area. It was as though we were being baked, not melted! We were all being changed into a new type of rock material called metamorphic. The high heat and pressure changed the texture, (the way the rocks feels), color and the structure of the atoms that made up our rock. The word Metamorphic comes from the prefix, meta, meaning change and morphic, meaning form or shape. Metamorphic rocks are very hard and dense, and often have wavy lines or bands of minerals compacted together, as in schist, or extremely flat layers like slate. Here are some before and after pictures of some common sedimentary rocks, that can become metamorphic rocks under heat and pressure. SEDIMENTARY ROCKS before they have been changed by heat and pressure: I was plain limestone I was old mud-stone or shale I was sandstone METAMORPHIC ROCKS that were formed from Sedimentary Rocks by heat and pressure in the crust. Now, I m beautiful marble! Now, I m flat slate! Now I m quartzite! Do not duplicate without permission from Orange County Department of Education. 15
My journey around and through the Rock Cycle is on-going, ever changing, and caused by many different forces acting deep within the earth. That is why they call it the Rock Cycle, because it keeps cycling, over and over. The processes that are constantly at work in the Rock Cycle are: On the surface: * weathering and erosion by wind, rain, ice, and glaciers erode rocks into sediments. Inside the Earth: * uplifting- the buried rock layers are uplifted to the surface by the Magma. * buried as new rock layers cover up old layers over time. * heat and pressure from the core, heats up or bakes the existing rocks. * melting the rock layers and returning them to the Magma. Thinking Back... Write and illustrate your own story of how a rock can change from one type to another. You may begin your story with any type of rock in the Rock Cycle. Be sure to include the PROCESSES that changed the rocks. For example: uplifting, erosion, heat and pressure. Visit: http://www.ivyhall.district96.k12.il.us/4th/kkhp/rocksandminerals/rockquiz.html Do not duplicate without permission from Orange County Department of Education. 16
Well, now that we have heard all about my life story, I d like to tell you a little more about how the surface of the earth can change over time! Some changes on the earth s surface take place slowly, such as weathering and erosion, by the wind, rain, and ice, while other changes take place very quickly, such as volcanoes, earthquakes, and landslides. Follow along as we find out more about these changes. Slow changes on the surface of the land are caused by weathering and erosion. Weathering is the process that breaks down large rock material into smaller rocks, pebbles, sand, and mud, which are called sediments. There are two types of weathering: Chemical and Physical. Visit: http://www.gpc.edu/~pgore/geology/geo101/weather.htm 1. Chemical weathering can occur when substances in the air, such as oxygen, carbon dioxide, and water can interact with the rocks and cause them to break apart or dissolve away over time. Chemicals that are found in acid rain or air pollution also cause rocks to break down and erode away. 2. Physical weathering is caused by the freezing and thawing of water. The water freezes and gets into the cracks of the rocks causing the ice to expand. When ice expands, the cracks in the rocks become wider and deeper, causing them to break apart easier. Rocks, such as granite, may also be eroded away by exfoliation, peeling away, layer by layer, or by an abrasion process, which wears away the surface of the rock by wind, water, and ice over time. Do not duplicate without permission from Orange County Department of Education. 17
Erosion is the process of transporting or moving sediments from one place to another by moving water, wind, rain or ice, and depositing them in a new place. Most changes to the surface of the land happen so slowly that you cannot observe them directly. Sometimes you can only see the results of the past changes over a long period of time, as in the formation of the Grand Canyon. Pictures of erosion: http://www.kented.org.uk/ngfl/subjects/geography/rivers/river%20articles/rivart.htm Faults are weaknesses or cracks in the earth s crust, which can produce both slow movements of the soil called creep or fast or rapid movements such as earthquakes. Visit: http://www.tinynet.com/faults.html Fast or rapid changes on the surface of the land are caused by earthquakes, volcanoes, landslides, and hurricanes. 1. Earthquakes can shake, uplift, bend and fold the land into new formations, creating shifts in rivers, lakes, hillsides, and mountains that last for thousands of years. Visit these websites: www.ivyhall.district96.k12.il.us/4th/kkhp/rocksandminerals/earthquakes.html http://www.earthquake.usgs.gov/learning/kids.php 2. Volcanoes can erupt suddenly through a crack or weakness in the earth s crust (fault), or where the chunks of the earth s crust, called plates, come together. A volcano may erupt and form a volcanic mountain in a quiet field, through a crack in the ocean floor, or blow the top off an old volcanic mountain in just a few hours or days. Visit these websites: http://volcano.und.nodak.edu, http://www.volcanoes.com/, or for video: http://www.learner.org/exhibits/volcanoes/meltrock.html Do not duplicate without permission from Orange County Department of Education. 18
3. Landslides, mudslides, and floods can change landforms quickly by transporting and depositing sand, rocks, and mud to other locations in just a few minutes. Usually, mudslides move wet soil and landslides move dry soil. 4. Hurricanes The energy from the high winds and rain might sweep away the shoreline and change the shape of the coastline in just a short time. Visit: http://yahooligans.yahoo.com/content/science/brainpop/movie?id=hurricanes Have you ever wondered how big rock boulders get moved from one place to another. They are s heavy, how can they move so far? Well, the answer is moving water! Moving water is the most powerful force there is for changing the earth s surface. Even a large drop of water can cause sand grains to splash 30 cm or 1 foot, or more, into the air! It can also move huge boulders, homes, buildings and even mountainsides. It is very powerful! Moving water can move soil, make cliffs fall down and carve canyons in solid rock. The Grand Canyon was carved by the action of the Colorado River and is about a mile deep. Visit: http://www.edu-source.com/gcpages/cvopage4.html Rivers pick up the sediment, move it downstream and deposit it in slow moving, flat areas along the riverbanks called flood plains. Some rivers deposit sediment in broad areas at the mouth of the river called deltas. Example -The Mississippi River Delta is one of the largest deltas in the world. At the shore, sediment from weathered cliffs is eroded by waves and deposited as new sand on beaches. Do not duplicate without permission from Orange County Department of Education. 19
Wind also erodes the surface of the earth by transporting or moving sediments from place to place. In the dry Southwest of the United States, wind erosion has shaped some of the world s most unusual landforms rocks that look like tables, arches, or columns. Visit: http://www.evsc.virginia.edu/~desert/wind/wind.html Wind erosion can also blow sand into large mounds called dunes that can be 325 feet (100 meters) high. Many sandy beaches have long stretches of dunes between the oceans and the interior land. Beach dunes are built by constantly blowing sea breezes. They help protect the land behind them during storms. http://www.nps.gov/whsa/factsheets.htm Ice in the form of glaciers can also change landforms. Glaciers are thin sheets of ice formed in the areas where more snow falls during the winter than melts during the summer. Glaciers are constantly moving very slowly, eroding sediment from one place and depositing it in another. http://nsidc.org/glaciers/story/grow.htlm There are 2 types of glaciers: high mountain valley glaciers, and continental glaciers. Visit: http://nsidc.colorado.edu/glaciers/ 1. Mountain Valley glaciers flow slowly down mountainsides, eroding the mountains under them. 2. Continental glaciers cover large areas such as Greenland and Antarctica. Do not duplicate without permission from Orange County Department of Education. 20 040606088