Big Idea 6 Earth Structures Part I

Florida Next Generation Sunshine State Standards:

SC.4.E.6.2 – Identify the physical properties of common earth-forming minerals, including hardness, color, luster, cleavage, and streak color, and recognize the role of minerals in the formation of rocks.

SC.4.E.6.4 – Describe the basic differences between physical weathering (breaking down of rock by wind, water, ice, temperature changes, and plants) and erosion (movement of rock by gravity, wind, water, and ice).

Terms

English Spanish Haitian Creole1. erosion erosión ewozyon2. igneous ígneo vòlkanik3. inorganic inorgánico inòganik (ki pa soti nan bèt

ou plant)4. metamorphic metamórfico metamòfik5. mineral mineral mineral6. organic orgánico òganik7. rock roca wòch8. sedimentary sedimentario sedimantè9. soil tierra/suelo tè

10. weathering meteorización/desgaste ewozyon physical weathering desgaste físico ewozyon fizik

Does This Matter to Me?

Have you ever thought about collecting rocks? Do you know anyone who collects rocks? Rocks are fun to collect; they come in all different shapes, sizes and colors. Have you ever cracked a rock open? Was the center of the rock a different color than the outside? Rocks can be found deep under the ocean floor or right outside your front door. The study of rocks is important because they can tell us information like the age of our Earth. Energy is constantly changing the features of Earth’s surface

by breaking down and moving rocks around. Let’s discover what moves rocks and makes them look so different.

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Talk about these questions in your group: How do rocks form? What are they made of? How are minerals classified? How is soil formed? What factors cause rapid change to the surface of

the Earth? What factors cause gradual change?

Rocks and Minerals(SC.4.E.6.2)

Rocks

Everyone can picture a rock, but do you know what a rock really is? Rocks are naturally occurring solid mineral deposits. The planet Earth is basically one big rock. You may have heard that the Earth is called "the third rock from the Sun." Rocks exist all over the Earth, in deep oceans, vast deserts, and high mountains. Rocks can be classified into three categories: igneous rocks, metamorphic rocks, and sedimentary rocks.

Igneous rocks are formed from molten lava that cools and hardens when it is exposed to the cooler temperatures of the Earth’s surface. Magma is melted rock that is found beneath the earth’s crust. Magma either escapes through the lava tubes and side vents of a volcano or intrudes into rock formations. An example of an igneous rock is granite, which is used for making stone buildings, floors, and sometimes kitchen counters.

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Metamorphic rocks are formed when other rocks are changed by high temperature and high pressure deep inside the Earth. An example of a metamorphic rock is marble. Marble is a common rock that statues are carved from, and is sometimes used to make bathtubs and bathroom sinks.

Sedimentary rocks are formed when small particles of minerals, sand, and soil (called sediments) settle on the bottom of lakes or oceans. The weight and pressure pushes down on these sediments over very long periods of time and slowly turns them into a sedimentary rock. A common example of a sedimentary rock is limestone. Limestone is one of the most common types of rock in Florida and is sometimes used in construction. Because it is porous, it sometimes erodes to form underground caves.

Where does sediment come from? Every day, rocks are being worn down by wind, rain, and ice. This process is called weathering. When rocks are washed into streams, rivers, lakes, and oceans, this is known as erosion. You will learn more about weathering and erosion later in this chapter.

Minerals

Earlier we said that rocks are naturally occurring solid mineral deposits. Minerals are the building blocks of rocks. A rock is usually made up of two or more minerals. Minerals are solid and can be found in nature. Over 4,000 minerals have been identified on Earth. Some minerals, like diamonds and amethyst, are very valuable and used to make jewelry. Geologists are scientists who explore rocks and identify minerals by making observations about their physical properties. There are several properties used to classify different minerals.

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Physical Properties Used to Classify Minerals

Property Description Graphic

Hardness

Moh’s scale measures the hardness of a mineral using the numbers 1-10. The

lower the number, the softer the mineral. The higher the number, the harder the mineral. Diamonds have a hardness of 10 and are the hardest

mineral.

Color Color is a way to describe a mineral to help identify it. Minerals vary in color.

LusterLuster indicates how light reflects from a

mineral's surface. For example, a mineral can have a metallic, glassy,

pearly, dull, or earthy luster.

CleavageThe way a mineral breaks indicates its cleavage. If it breaks along a smooth,

flat surface, the mineral has cleavage. If it is jagged when broken, it fractures.

Streak Color

Streak color of a mineral is found by rubbing it on a rough, hard surface

called a streak plate. The color of the powder is the mineral's streak color.

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Properties of Some Common Minerals

Mineral Graphic Hardness Color Luster Cleavage Streak Color

Talc 1 – very soft

white, green, brown or gray

waxy or greasy

thin, flat sheets white

Graphite 1.5 – very soft black metallic or

dull

thin, flexible flakes

black

Mica 3 – softreddish, green or white

pearly or metallic

thin, flexible sheets

white

Calcite 3 – soft varies glassy six-sided crystals white

Feldspar6 – somewhat hard

light pink, gray, green or white

glassy

uneven or smooth and shell-like

white

Pyrite6 – somewhat hard

yellow metallic smooth, shell-like

greenish black

Quartz 7 – hard varies glassy none white

Diamond 10 – very hard

blue, yellow, colorless, red, orange, green, brown

waxy or nonmetallic

perfect, octa-hedrons

white or none/ diamond is harder than the streak plate

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Weathering and Erosion(SC.4.E.6.4)

Weathering

Weathering is the natural process of rock and soil material being worn away. The process of weathering can be caused by running water, wind, ice, plants, temperature changes, and waves. All of these weathering processes break down rocks into smaller pieces. The breaking of rocks by the forces of water, waves, wind, ice, and pressure from plant roots are all examples of what is called physical weathering.

The picture is an example of what happens during physical weathering. During a storm, for example, water enters the many holes that are in the rock. When this water freezes, it expands. The expansion of the ice results in the holes or cracks getting wider. Over time, this process makes large cracks.

Most weathering happens very slowly over long periods of time. Sometimes weathering can happen very quickly from severe floods, storms, mudslides, or hurricanes.

Soil

Weathering is a process that helps to make soil. Soil is another word for dirt. Soil is a mix of organic and inorganic materials. Organic means that it came from living things and inorganic means that it came from non-living things. The inorganic materials in soil come from rocks. Through the process of weathering, rocks eventually break down into very small particles. Then these inorganic particles mix with organic particles from dead plants and animals that are decomposing. Soil can look and feel different depending on the materials that form the soil in a particular place.

Erosion

Erosion is the process of moving rocks and soil by water, wind, ice, and gravity. Most erosion is caused by moving water and wind. Rainfall, storms, and melting snow are some causes that can lead an area of land to get more water than it can absorb. The excess water, called runoff, will move loose soil, rocks, and debris, and carry them to the lowest level it reaches when the water levels go down again. This runoff permanently erodes the rocks and soil and moves them from one place to another. Erosion is greater in areas where the soil is bare and there are not many plants holding the soil together by their roots. Also, if the slope is steeper, such as on a mountain, the runoff will have greater force and will pick up soil and rocks and carry them more easily. In addition, some soil types are more easily carried away by flowing water than others.

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Wind is another cause of erosion, especially in dry climates where there are few plants. Wind that blows across bare land can lift particles of sand and soil, but leaves behind heavier pebbles and rocks.

In many parts of the world, ice, in the form of glaciers, has caused huge amounts of erosion over time. Although a glacier moves slowly, the heavy ice grinds down and picks up all the loose materials as it travels over. When the ice melts, smooth, bare rocks are left behind along with everything else the glacier was carrying.

Ocean waves also cause erosion. Where the ocean meets the land, waves and currents cause coastal erosion of cliffs and beaches. Thus, different types of erosion cause the features of Earth’s surface to look different. The smooth bare rocks are left after glaciers pass, and the more jagged rocks are eroded by wind, rain, and flooding.

There are many types of erosion, but water erosion generally causes the most problems. Farmers, home owners, and park and beach managers all have to worry about the possible damaging effects

of water eroding away their land.

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Bryce Canyon National Park in Utah contains structures called hoodoos formed

from wind, ice, and water erosion on sedimentary rocks.

Fill in the following boxes about weathering and erosion:

Describe the basic differences between physical weathering and erosion.

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In Inquiry 9 below, you will investigate how erosion occurs. You will explore some of the factors that can increase or decrease erosion. Erosion can cause a lot of damage, but some things can be done to limit or reduce the amount of erosion.

Inquiry 9: Stream Table(SC.4.E.6.4)

This activity divides the experiment among groups:Group 1: ControlGroup 2: SlopeGroup 3: Soil TypeGroup 4: Plants

Inquiry Framework1. Questioning State the problem

What effect does slope, soil type, or plants have on the amount of runoff produced during erosion?

Make predictions1. How does slope affect the amount of runoff produced during

erosion?

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2. How does soil type affect the amount of runoff produced during erosion?

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3. How do plants affect the amount of runoff produced during erosion?

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2. Planning Read the materials and procedures Do I know which group I am in and what materials I need?

Yes No

Make a plan for testing the effect of the one variable your group will manipulate – slope, soil type, or plants – on the amount of soil erosion as compared to the control. Explain how you are going to keep track of your observations. Compare your plan with the procedures given for your group. Now go through the written procedures and highlight the procedures for your group (Group 1, 2, 3, or 4).

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3. Implementing Gather the materials

For all groups: highlighter for each group member 2 aluminum roasting pans

1 with a pre-punched hole, the diameter of a pencil, at one end (see diagram on the next page)

1 with no hole to catch runoff 1 250 ml graduated cylinder 1 large plastic cup or pitcher 1 ruler masking tape

For varying groups: Group 1: Control – Bag of soil, 2 textbooks (approx. 2 cm in height each)

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Group 2: Slope – Bag of soil, 4 textbooks (2 cm each) Group 3: Soil Type – Bag of sand, 2 textbooks (2 cm each) Group 4: Plants – Bag of soil, handful of grass, 2 textbooks (2 cm each)

Follow the procedures1.

Groups 1, 2, and 4: Add soil to cover 24 cm from the end of the pan opposite the hole. The soil should be 2 cm deep. Do not press or pat down the soil.

Group 3: Add sand to cover 24 cm from the end of the pan opposite the hole. The sand should be 2 cm deep. Do not press or pat down the sand. (It should look the same as above, except with sand instead of soil.)

2.Group 1: For control, raise the height of one end of the pan filled with soil. Place 2 textbooks underneath, so that the pan is tilted. You may use masking tape to hold the pan in place.

Group 2: For slope as test variable, use 4 textbooks to raise the slope.Group 3: For soil type as test variable, use 2 textbooks for the slope.Group 4: For plants as test variable, plant the handful of grass into the soil. Use 2 textbooks for the slope.

3.All Groups: Arrange the pan so that the hole is slightly hanging over the edge of the desk. Align the hole over the second pan on the floor to

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collect excess runoff.

4. Using a graduated cylinder, measure 500 ml of water into a large plastic cup or pitcher.

5. Slowly (see picture) pour 500 ml of water in one spot near the center top of the soil. Pour the water from a height of approximately 30 cm.

6. Have one group member hold the graduated cylinder under the hole to catch runoff as it falls through the pan. (Any excess will be caught in roasting pan, as shown in the picture for step 3.)

7. Wait 5 minutes as runoff flows through the pan.8. Using the graduated cylinder, measure the amount of runoff

from each pan.9. In the box below, draw and label what you observed in your

group’s pan:

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4. Concluding Draw a conclusionWhat did you find out? Briefly describe what you learned:

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1. How did slope affect the amount of runoff produced during erosion?

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2. How did soil type affect the amount of runoff produced during erosion?

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3. How did plants affect the amount of runoff produced during erosion?

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4. Compare what you thought would happen with what actually happened. Did the results support your predictions or not?

Use this model to help with your response:

I predicted that __________. The results of the investigation did or did not support my predictions because I learned from my observations that __________________________

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5. Reporting Share your resultsWhat do you want to tell others about the activity?

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Talk with your group members and answer the following questions:

1. What could a farmer do to reduce the erosion on his farm? How would the data from this investigation help?

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2. What could the managers of a beach-front park do to reduce the erosion on their beach? How would the data from this investigation help?

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3. The control pan was the one that was filled with soil, had no grass, and had 2 textbooks underneath. Why was it important to have a control pan?

6. Inquiry

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Reflect on your results If I did this activity again, how would I improve it?

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Extension What would be a good follow-up experiment based on what I learned?

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7. Application Make connections How does this activity relate to what happens in the real

world? How could I apply the results in new situations?

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Erosion is the process by which weathered materials are carried away. In the case of the activity above, materials were carried away by moving water. If you worked with the “slope” variable, you have learned that rain or the water from melting snow forms streams and travels from higher to lower elevations. This moving water causes erosion. If you worked with the “soil type” variable, you have discovered that some soils absorb more water than others. As a result, these soils slow down the process of erosion. If you worked with the “plants” variable, you have found out that plants also help to slow down the process of erosion because the plant roots help to hold the soil in place. In beach areas, people place barriers to slow down the erosion of sand.

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You learned about the solid materials that compose the land surfaces of the Earth. Rocks are naturally occurring solid mineral deposits. There are three main types of rocks. Igneous rocks are formed from molten lava that cools quickly when it reaches Earth’s surface. Metamorphic rocks are formed when other rocks are changed by great heat and pressure deep within the Earth. Sedimentary rocks are formed from small particles called sediments that settle on the bottom of lakes or oceans. The weight and pressure of the water slowly turn the sediments into rock.

Minerals are the building blocks of rocks. Rocks are usually made up of two or more minerals. Minerals are classified based on properties such as hardness, color, luster, cleavage, and streak color.

Water and wind are sources of weathering that lead to rocks being broken down into sand and soil. Weathering is the process by which material is worn away. The breaking of rocks by the forces of water, waves, wind, ice and pressure from plant roots are all examples of physical weathering.

You also learned that erosion is the process of moving rocks and dirt by water, wind, or gravity. You did an activity that modeled how erosion is affected by factors such as slope, soil type, and plants. Erosion from flowing water is one of the most common types. Erosion is one of the forces that cause the surface of the Earth to constantly change its appearance. Some of these changes are caused by slow processes (like river erosion). Other changes are caused by fast processes (like beach erosion from a hurricane).

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Earth Structures Part IEarth Structures Part I

Assessment

1.

After a visit to the Grand Canyon in Arizona, Jamie wondered how a river could carve such a deep canyon. Her grandfather created a model to show the formation of the Grand Canyon. He took a glass pan and filled it with tightly packed soil. He raised the pan slightly at one end. Then he took a beaker filled with water and slowly began to pour it on the raised end of the pan. He filled the beaker with water several times and repeated the process. Every time he poured more water onto the soil, the water flow would form deeper gaps along its path into the soil.

Describe the similarities between the formation of the Grand Canyon and Jamie’s grandfather’s model.

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2. The freezing and thawing action of water affects a rock by

a. Transforming the rock into igneous rockb. Chemically changing the rockc. Gradually breaking down the rock into smaller piecesd. Leaving behind sedimentary particles from evaporated solutions

3. Which of these can cause sharp, rough mountains to become rounded and smooth over time?

a. Wind and rainb. The sun’s raysc. Light and darknessd. Earth’s magnetic field

4. All of the landforms on Earth are constantly changing shape. What is most responsible for the changes in the landforms?

a. Earthquakesb. Water erosionc. Pollutiond. Wind

5. On flat open farmland, farmers often plant a row of trees as a method of soil conservation. Which statement best explains how a row of trees can help conserve soil?

a. The trees provide shade, so the soil does not dry out.b. The tree branches protect the soil from the force of acid rain.c. The trees act as a windbreak, reducing soil erosion caused by blowing wind.d. The trees attract animals whose wastes add fertilizer to help prevent soil erosion.

6. There are three types of rocks – igneous, sedimentary and metamorphic. Describe how each type of rock is formed.

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7. The table below shows whether or not each mineral can scratch the other minerals.

Based on the table, which mineral is the hardest?

a. Mineral Ab. Mineral Bc. Mineral C

8. Daunte performed several tests on a mineral to help identify it. The picture below shows one of the tests he performed.

Which property of a mineral will he be able to identify using this test?

a. Attraction to magnetsb. Streak colorc. Hardnessd. Cleavage

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