Learning Objectives

After this lesson, students should be able to:

• Describe the basic ideas of stress.
• List the three different types of weathering.
• Explain that not all rocks break the same way or with the same amount of pressure.
• Describe how engineers are able to evaluate the strength of rocks.
• Develop a model of the rock cycle

Worksheets and Attachments

Introduction/Motivation

(Optional: Introduce the lesson using the Rock Solid Introduction PowerPoint presentation. Use the written text below as a script, with each idea correlating to one slide.)

We see rocks outside everyday, in both landscaping and nature. In fact, the entire earth is basically one gigantic rock! The earth's crust is entirely made of solid rocks, so there are huge rocks in the ground covering the entire planet! We cannot see many of these rocks. Sometimes dirt covers them and we must dig very deep to find them, but huge rocks cover the entire earth's crust, even under the oceans. That means that all of our buildings, all of our bridges, all of our roads, and even your home, are sitting on rock.

What might happen if some of these huge rocks broke? What types of natural disasters might be caused? What would happen to the bridge or skyscraper resting upon one of those massive rocks? These are questions that geotechnical engineers think about when determining locations to place structures. Geotechnical engineers understand what causes rocks to break. They know how to identify different types of rocks, and determine if a certain rock is likely to break. They work with structural engineers to plan the best way to build structures in different rock conditions.

Why Care about the Strength of a Rock?

The most important reason why we care about the strength of a rock is that when a large rock breaks, it can be a hazard and possibly cause a disaster. There are many different disasters caused by breaking rocks, including earthquakes, tsunamis, volcanoes, rock falls, and landslides. To protect structures and people, we want to be able to predict or prevent such disasters. If an engineer knows the characteristics of a particular rock type, she may be able to predict or prevent disasters.

Furthermore, a less serious reason why we care about the strength of rocks is for development, which means building and expanding the use of land (such as new shopping centers, schools or homes being built in a town). Many building plans require deep foundations, making it necessary to excavate or dig out rock. An engineer provides information about the best way to excavate the rock, so as to build an adequate foundation.

What Can Break Rocks?

When pressure is applied to an area, such as a rock, it is called stress. If you press your hands together, you can feel the forces of stress. In nature, stress can cause rocks to break, and one way that stress occurs is by the natural movements of the earth's crust (remember that the earth's crust is basically floating on liquid magma, and so it moves often). Refer to the associated activity Soapy Stress for a fun and hands-on approach to learn more about stress! There are three types of stress (see Figure 1).

Compressional stress is when a rock is pressed together into itself, like when crust movements cause two rocks to squeeze another one between them. Another example is when mountains are formed at a convergent boundary, like the Rocky Mountains. Press your hands together again. You can feel that the inner parts of your hands are being smashed by compressional stress from the muscles in your hands pushing inward.

T ensional stress is when a rock is pulled apart. For example, if a rock wedged itself into the crack of another rock, and movement of the earth's crust caused it to wedge even further until the rock broke apart. Another example is a divergent boundary, like the Mid-Atlantic Ridge, which is formed by two tectonic plates pulling apart from each other to allow lava to flow upward. Use one of your hands to pull a finger on your other hand. You can feel the tensional stress because your hand is pulling your finger one way, and your other hand is attached to your finger, pulling it the other way by holding it in place.

Shear stress is when a rock is pulled on one side but pushed on the other side. This can happen if the crust movements on one side of a rock are opposite of those on the other side of the rock. An example of this is the San Andreas Fault, which is on a transform boundary, with the California plate moving southward and the Pacific Ocean plate moving northward. Put your hands together again, but this time press upward with your right hand and downward with your left hand. If you press hard, you should notice that the skin on your right hand is being pulled down because of the forces from your left hand pulling down, and the skin on your left hand is being pulled up because of your right hand. (It may be easier to see the skin being pulled if you use an area on your body where the skin is looser, such as your hand pressing upward against your arm or cheek.)

In addition to stress due to the movement of the earth's crust, stress can come from weathering. Weathering is the breaking down of rocks into sediments (small bits of rock), due to conditions in nature. There are many types of weathering:

• Physical weathering is when a physical action breaks the rock, such as the forces of wind or water. A common example is the freeze/thaw action of water in rock cracks. As the water freezes, it expands, causing stress (pressure) that breaks the rock. (Note: If students ask what kind of stress this is, tell them that the process is complicated and includes both tensional and compressional stress.)
• Chemical weathering is when the rock is chemically broken down. Some common examples of this are rust forming on granite or acid rain breaking down limestone. This type of weathering is not considered a type of stress because there is no pressure on the rock (remember that stress is pressure applied to an area).
• Biological weathering is when living organisms break the rock. A typical example is a tree root breaking a rock due to the stress caused by its pressure. (Note: If students ask what kind of stress this is, tell them that the process is complicated and includes both tensional and compressional stress.)

So, rocks in the earth are usually broken by either the stress from the movement of the crust or the stress from weathering.

Upon What Does the Strength of Rock Depend?

Not all rocks break from the same amount of pressure. Some rocks are easier to break than others. The strength of a particular rock depends on that rock's type, texture and chemical composition. It also depends on the presence or absence of fluids, or if there are internal structures.

Sometimes, it is possible to predict where a rock will break. Rocks often break along a plane of weakness, which is the weakest part of the rock's structure. Sedimentary rocks have planes of weakness along their bedding planes, or between the layers of sediment. Metamorphic rocks have planes of weakness along their foliation planes, which are layers or stripes formed from pressure. Observing these aspects helps us predict where a rock will break!

How Do Engineers Find the Strength of a Rock?

To discover all the factors that determine whether a rock might break, engineers use certain methods and equipment. They examine the rock's texture and structure. They drill to get rock samples, called core samples (see Figure 2). They test the sample's response to stress using special (and expensive) machinery. As a side note, one problem with testing samples is that rocks are not homogeneous, meaning one sample's response to the test may not necessarily be identical to the response of another sample taken elsewhere. After an engineer has fully examined and tested a rock, she gives it a safety factor for others to consider when building near the rock.

Lesson Background and Concepts for Teachers

What Makes Up Rocks?

Knowing what makes up rocks might help us understand their strength. Rocks are made of minerals. Rocks are classified into different types, depending upon their mineral composition and formation. First let's look at minerals.

A mineral is a solid material that exists naturally on earth, and is made of only one substance. Most minerals are made up of crystals, which are solid, 3D patterns made by the molecular structure. There are hundreds of different minerals, and they are classified by their chemical makeup and crystal shape. Some familiar minerals include: gold, silver, platinum, mercury, sulfur, graphite, mercury, diamond, talc, halite (table salt), calcite, galena (lead), magnetite, hematite, quartz and mica.

Minerals can be identified by conducting a series of tests, and comparing the results to charts of known mineral characteristics. The tests include finding their color, streak (the color of the mark they leave when you rub them on something), transparency, hardness, luster (shininess), cleavage (the specific way that they break) and crystal shape. Students can further investigate these properties with the associated activity Rocks, Rocks, Rocks: Test, Identify Properties & Classify.

What is the difference between a rock and a mineral? Rocks are made of two or more minerals. For example granite, a very common rock, is made of the minerals, feldspar, quartz, mica and hornblende, which can actually be distinctly seen in granite (see Figure 3).

How are Rocks Made?

Besides its mineral components, a rock type is also determined by the way it was formed. The three basic ways that rocks are made are grouped as the three rock families: sedimentary, igneous and metamorphic.

• Sedimentary rocks are made of sediments (small bits of old rock). Sediments come from the weathering and erosion of old rocks. Weathering is how rocks are broken down, usually from influences such as water and air. Erosion is the breaking down and movement of parts of the earth's surface (weathering is a type of erosion). Once sediments are broken apart from weathering and erosion, then pressure pushes them together (called compaction) to make a layer of rock. Cementation also holds sediments together, which is when salts crystallize as water is squeezed out. Later, other sediments get pushed into another layer of rock and eventually the layering, or bedding, continues to make one bigger rock. This process creates layers that are characteristic to sedimentary rocks (see Figure 4). Some common sedimentary rocks are sandstone, siltstone, limestone, conglomerate and shale.

• Igneous rocks are made of magma, which is molten rock (old rock that has been melted from pressure and heat under the earth's crust). Magma is called lava after it comes out of the crust (for example, when it comes out of a volcano). When the liquid magma or lava cools, it becomes hard, forming an igneous rock. The name "igneous" comes from the Latin word "ignis," which means fire. Different types of igneous rocks are formed if they cool slowly below the earth's surface (called intrusive) or quickly above the earth's surface (called extrusive). Some common igneous rocks are basalt, gabbro, granite (see Figure 3), pumice and obsidian.
• Metamorphic rocks are formed from any type of existing rock. Pressure and heat change the actual molecules of a rock's minerals so that it becomes an entirely different rock (without melting, which would make it an igneous rock). The type of metamorphic rock formed depends on what type of rock it started out as. Foliation is when the pressure squeezes the minerals in a rock to create lines or layers. Foliation is a typical metamorphic rock characteristic (see Figure 5). Some common metamorphic rocks are gneiss, slate, marble and schist.

Rock Cycle

You may have noticed in learning about the different rock families that all new rocks are made from old rocks. This is the idea behind the rock cycle (see Figure 6). For example, under certain geophysical processes, a metamorphic rock can be formed from a sedimentary and/or igneous rock. Likewise, all rocks can become every other type of rock given the right circumstances. The rock cycle describes the processes that allow the creation of new rocks from old rocks. [See the Develop Your Own Rock Cycle Worksheet that allows students to develop their own rock cycle].

Lesson Closure

So, why do we care about how rocks break? Rocks make up all of the earth's crust. It is natural for rocks to break, depending upon the stresses on them. When designing structures, engineers carefully examine the underground and above ground rocks before they build roads, homes or towers. How do we know if an area of land is safe to build around? Engineers identify rocks by close examination and testing samples under stresses. Since different rocks have different strengths, engineers can estimate how much stress a particular rock can handle.

In this lesson, we learned about what knowledge geotechnical engineers use to hypothesize about rocks. We learned that rocks break from stress, which can come from the earth's crust moving or weathering. We also learned that whether or not a rock breaks depends on many factors, and we can sometimes guess a rock's plane of weakness. Now that we know all this, we can predict if and how a rock might break, just like a geotechnical engineer!

Vocabulary/Definitions

compressional stress: When something is being pressed together.

earth's crust: (geology) The outer layer of the earth.

erosion: Natural processes that wear away material. Includes weathering, dissolution, abrasion, corrosion and transportation.

geotechnical engineer: A person concerned with the engineering properties of earth materials. They investigate the soil and rock below ground to determine its properties, and then design foundations for human-made structures built on the ground, such as buildings or bridges. They design structures built in or of soil or rock. They also assess the risk to humans, property and the environment from natural hazards such as landslides, debris flows and rock falls.

homogeneous: Uniform in structure or composition throughout.

igneous rock: (geology) A rock made of cooled magma (or lava), which is molten rock melted from pressure and heat under the earth's crust.

metamorphic rock: (geology) A rock formed from any type of existing rock, in which minerals are changed in structure or composition by pressure and heat. Examples: basalt, granite, pumice and obsidian.

mineral: A naturally-occurring, homogeneous inorganic solid substance having a specific chemical composition and characteristic crystalline structure, color and hardness. Examples: gold, silver, platinum, sulfur, graphite, diamond, talc, quartz and mica.

plane of weakness: An area of the weakest part of a rock's structure.

rock: A naturally-formed aggregate of mineral matter constituting a significant part of the earth's crust.

rock cycle: All new rocks are created from old rocks. Different rock types depend on their forming process.

rock falls: A fall of rocks, as from a cliff. Often caused by weathering.

sedimentary rock: (geology) A rock made by the deposition of sediment (small bits of old rock). Examples: sandstone, siltstone, limestone and shale.

shear stress: When something is being pulled one way on one side, and the opposite way on the other side.

stress: Pressure applied to an area. The three types are tensional, compressional and shear.

tensional stress: When something is being pulled apart.

weathering: Breaking down of rocks, due to such things as water, wind, acid rain and plants.

Assessment

Pre-Lesson Assessment

Brainstorming: As a class, have students engage in open discussion. Remind them that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Have students raise their hands to respond. Write their ideas on the board. Ask the students:

• Of what material(s) is the earth's crust made? (Possible answers: Rocks, dirt, etc.)
• How do rocks break in nature? (Possible answers: Pressure, running water, freezing water, plant roots, weathering, rocks falling on rocks, actions of people.)
• How would the breaking of a large rock affect people? (Answer: Lead students to the idea of earthquakes, structures falling, tunnel or foundation collapsing, volcanoes, rockslides, etc.)

Post-Introduction Assessment

Voting: Ask a true/false question and have students vote by holding thumbs up for true and thumbs down for false. Tally the votes and write the totals on the board. Give the right answer.

• True or False: Under the ocean's floor, there are large rocks. (Answer: True. Large rocks cover the entire earth's crust, including under the oceans.)
• True or False: Geotechnical engineers study buildings and how they stand. (Answer: False. They study rocks and the earth.)
• True or False: Geotechnical engineers can guess if a rockslide might occur at a certain location. (Answer: True. These engineers know how to identify rocks and the ways they can break.)

Lesson Summary Assessment

Worksheet: Have students complete the Rock Solid Worksheet; review their answers to gauge their mastery of the subject.

Drawing: Have students draw a picture of each of the different types of stress. Ask them to draw arrows that show which way the pressure is acting and identify each type of stress. Have them draw another picture illustrating their choice of any example of weathering.

Lesson Extension Activities

Conduct the Adventure Engineering unit, Asteroid Impact, an 8-lesson unit in which student teams are posed with the scenario of an impending earth-crashing asteroid. They must design the location and size of underground caverns to save people from an earth that will be uninhabitable for one year. Student teams explore general and geological maps, determine the area of their classroom to help determine the cavern size required, learn about map scales, test rocks, identify important and not-so-important rock properties for underground caverns, and choose a final location and size.

Additional Multimedia Support

Show students the attached Rock Solid Introduction PowerPoint slide presentation.

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Learning Objectives

After this lesson, students should be able to:

• Draw a complete, labeled diagram of the rock cycle.
• Explain why engineers must know about rocks when developing land or designing new structures.

Worksheets and Attachments

Pre-Req Knowledge

Students should be familiar with the different types of stress and weather related to rocks, as presented in the Rock Cycle unit, lesson 1: Rock Solid.

Introduction/Motivation

Today we are going to learn more about something that you walk over every day—rocks! To get started, can anyone tell my why engineers need to know about rocks? Engineers must know about rocks, how they are formed, and how strong they are so that they can design safe buildings, tunnels and bridges for us. Engineers also use their knowledge of rocks to help determine and prevent natural disasters to humans from rock falls, landslides and earthquakes. These natural hazards can all be caused by breaking rocks.

How are rocks made? Can they change over time? This can be explained by understanding the rock cycle. Let's look at a diagram of the rock cycle together and talk about the different steps. (By paper handout or overhead projection, show students the rock cycle diagram in the Rock Cycle Handout-Overhead. Make sure they understand that the rock cycle continually repeats over many, many years.)

Weathering, erosion, cooling, melting, pressure, compaction, cementation, and heat are all factors that affect the breakdown and formation of rocks. Even though rocks seem so strong to us, they can be forced to change when their environmental conditions change. The three main types of rock can all change—igneous, sedimentary and metamorphic rock. All three types can be melted into magma under the earth's surface, which then hardens into igneous rock. Extreme heat or pressure can change rocks into metamorphic rocks. Rocks that are exposed to the atmosphere can undergo weathering and erosion to break into smaller pieces (sediment) that can be affected by pressure or cementation to form sedimentary rocks.

The rock cycle is a very slow cycle. Rocks might take a thousand years to change into another type of rock. In the rock cycle, rocks are continuously (although slowly) being changed from one form to another. The rock cycle proceeds in no particular order. For example, igneous rock can change into metamorphic or sedimentary rock over time, and metamorphic rock can become sedimentary or igneous.

Engineers use the rock cycle to help them understand the geology of region. Geotechnical engineers understand the rock cycle, what causes the rocks to break, and how a rock reacts when exposed to different environmental factors. These engineers are the people to contact when you want to develop a new area of houses or stores on land that has never been built upon before. These engineers are able to identify different types of rocks and soils in an area, and determine if the rocks may break if exposed to new forces, such as the pressure from vehicle traffic, structures and people. These engineers also study how changes to the area might cause unwanted side effects and risks to humans and property, such as landslides, unstable ground, and rock falls. In this way, they keep us safe by predicting and preventing natural hazards. Engineers must consider the environmental effects of their interactions with the earth and rocks, and how the addition of a structure or removal of some rocks might impact the stability of the area, increasing the risk of natural disasters and causing damage to structures over time. Following the lesson, students can play the fun game of Rock Jeopardy! through the associated activity to reinforce their understanding of rocks, the rock cycle and geotechnical engineering. 

Lesson Background and Concepts for Teachers

The rock cycle explains the series of changes that rocks go though as they slowly are altered from one form into another. Key concepts for students to understand are that the rock cycle is a slow and continuous process, occurring over thousands of years, and that rocks change from one form to another under heat, weathering, erosion, melting, cooling, pressure, compaction and cementation.

The rock cycle is a continuous series of steps. For example: when igneous rock undergoes weathering and erosion it becomes sediment. Then, when that sediment undergoes compaction and cementation it becomes sedimentary rock. If that sedimentary rock becomes pressed together by heat and pressure, it can turn into metamorphic rock. Metamorphic rock, when it undergoes melting, becomes magma. That magma, when it cools, can become igneous rock—and the cycle continues!

In addition to going around the circle, changes in rocks can also occur across the circle—igneous rock can become metamorphic rock under heat and pressure, and metamorphic rock can become sediment under weathering and erosion.

While these concepts are fairly straightforward, it is worth taking the time to make sure that students can both draw the diagram of the rock cycle and explain the different steps. Additionally, you may need to review with the students the different processes that occur in the cycle: heat, pressure, melting, cooling, weathering, erosion, compaction and cementation. Refer to the Vocabulary/Definitions section and lesson 1 of this unit for explanations of several of these terms.

Lesson Closure

What have we learned today? What factors can affect rocks? What factors cause the breakdown and formation of rocks? (Collect answers from students: Weathering, erosion, cooling, melting, pressure and heat.) So basically, rocks can be forced to change when their environmental conditions change, and these changes can be described using the rock cycle. What is the order of the rock cycle? (Answer: The rock cycle goes in no particular order.) Explain to me how it works. (Answer: Rocks and minerals can go around the rock cycle in a circle, and changes to rocks can also occur across the circle. For example, igneous rock can become metamorphic rock under heat and pressure, and metamorphic rock can become sediment under weathering and erosion.)

Engineers use the relationships described in the rock cycle to help them understand the geology of an area of land. What do they want to find out? (Answer: Geotechnical engineers study the rock cycle, what causes rocks to break, and what reaction might occur when a rock is exposed to different environmental conditions, including heat and pressure.) Engineers use their knowledge of rocks and the rock cycle to create technologies to help predict and avoid causing natural hazards, such as ____________ and _______________ (Answers: landslides and earthquakes). They also evaluate the impacts and risks to humans and the environment that might be caused by our development of housing and industrial areas.

Vocabulary/Definitions

cementation: The act or process of cementing. Another part of how sedimentary rocks are formed is by sediment being glued together by natural glues such as calcite and silica. Compaction and cementation work together to create sedimentary rocks from sediment.

compaction: The act of pressing something together. Part of the way sedimentary rocks are formed is by sediment being compacted together.

erosion: The process by which the surface of the earth is worn away by the action of water, glaciers, winds, waves, etc.

magma: Molten rock inside of the earth.

sediment: Material deposited by wind, water or glaciers.

weathering: In geology, the various mechanical and chemical processes that cause exposed rock to decompose.

Assessment

Pre-Lesson Assessment

Warm up Question: Write the following question on the classroom board and have each student take a moment to write down their own answer. Walk around, looking at what students wrote, marking their answers if correct, and gauging the class' understanding of the subject. Consider making the "correct" mark by using a rubber stamp and a colorful ink pad.

• Why do engineers need to know about rocks? (Possible answer: Because engineers must design strong foundations, structures, bridges and tunnels to keep us safe.)

Post-Introduction Assessment

Drawing: Ask students to draw the complete rock cycle, starting with blank paper. Remind them to include all the steps, and label all the arrows between the different parts of the cycle. Hint: Note the five main "stops" along the cycle, and nine arrows (as shown in the Rock Cycle Handout-Overhead). Next, review the entire diagram as a class to make sure that everyone has all the parts drawn in and correctly labeled. Help students fill in any missing parts of their rock cycle diagrams and review the entire cycle with the class.

Class Voting: Ask a true/false question and have students vote by holding thumbs up for true and thumbs down for false. Tally the votes and write the total on the board. Give the right answer.

• True or False: Geotechnical engineers study the rock cycle. (Answer: True)
• True or False: The rock cycle can help engineers predict natural hazards. (Answer: True)
• True or False: All engineers use the rock cycle in their work. (Answer: False. Many engineers use the rock cycle, especially civil and geotechnical engineers. However, many other types of engineers do not use the rock cycle in their work.)
• True or False: Engineers use the properties of rocks to determine the best place to build a structure. (Answer: True)
• True or False: Geotechnical engineers determine the risks to humans, property and the environment from natural hazards. (Answer: True)

Lesson Summary Assessment

Where to Build It? Engage students in a discussion about how engineers use their understanding of the properties of rocks and the rock cycle when designing a structure, such as a house, a dam, or even a wind turbine. Have students look at the Rock Cycle Handout-Overhead. At what place on the rock cycle would provide the best conditions to build a structure? On sedimentary rock in an area that gets lot of rain? All rocks can change over time. As an engineer, what factors should you consider when choosing the best place to build a house? (Possible answers: Weather conditions, range of temperatures, types of rocks, etc.)

Lesson Extension Activities

Rock Cycle Race: As a timed race, ask two students at a time to volunteer to draw the rock cycle (appropriately labeled) on the board. The first student to correctly draw the entire cycle wins.

Research Project: Have students identify an engineering design (such as a specific bridge, tunnel or building) and research the particular issues its engineers would have needed to know about the rocks underlying the structure. Have students write a one-page report describing the structure, the rock formations under it, and the associated risks to the environment from the development of the structure (if any).

References

Copyright

Contributors

Supporting Program

Learning Objectives

After this lesson, students should be able to:

• Define fossil.
• Describe how fossils are formed.
• Explain why engineers might study fossils.

Introduction/Motivation

Today we're going to learn about some extremely old stuff—fossils! What are fossils? How are they formed? Why do scientists and engineers care about them? Let's start off with the definition of a fossil: Can anyone explain what a fossil is? A fossil is a remainder of something that lived a long time ago, such as an ancient plant or animal. Most fossils actually come from species that are now extinct.

Fossils help us learn about how the Earth, plants, and animals have changed over time. They also help us better understand the history of the Earth. Paleontologists (scientists who study fossils) can identify a time period for a certain fossil because the oldest fossils are the deepest buried. This makes sense because fossils are formed when soil covers a dead organism, and the hardest parts of the organism leave an imprint in the soil. So, over time, the soil covers more and more organisms, piling on top of the older fossils.

How is engineering related to fossils? Engineers are always trying to get new ideas and be inspired by things. By studying fossils, they can better understand how the prehistoric world worked, and find out details about specific processes. For example, studying pterodactyl bones can help a paleontologist understand exactly how the pterodactyl was able to fly. Engineers can compare and contrast the pterodactyl flying process to other flying methods. They might ask questions such as: Is there anything different and beneficial that the flight process includes? Is the pterodactyl flight process more efficient than other flight processes in any way? Is there anything in the pterodactyl flight process that we should avoid? How successful was the pterodactyl flight process? Engineers ask these types of questions to improve designs for current technologies. When engineers use processes from nature to improve a modern technological process or object, we call it biomimicry.

Engineers design the tools that help discover fossils. Paleontologists once only used hand picks and magnifying glasses to locate fossils. Now they use advanced tools such as magnetic resonance imaging, computer-assisted tomography, and mass spectrometry. Engineers also are involved in the design of technologies that create three-dimensional images of whole organisms from the two- dimensional imprints of fossils. To animate these new 3D images, they study the parts of the organism to discovery how the organism may have moved. Also, the instrumentation used to create chemical models of organisms from fossils is developed by engineers. Chemical analysis of fossils can help us learn more about the environment in which the organism lived, the diseases during that time, and what the organism used for food. Lastly, engineers can also use fossils and fossil fuels to create materials and energy that we use every day.

Lesson Background and Concepts for Teachers

What is a fossil?

A fossil is a remainder of something that lived a very, very long time ago. It can be the image of a plant, animal or even just the trace of an animal, such as its dung or tracks. Refer to the Fossil Fondue activity to have students learn more about how fossils are created by forming their own using small toy figures and melted chocolate.

How are fossils formed?

Animal fossils are formed when an animal dies and slowly becomes covered with soil, mud or silt. Over thousands and thousands of years, the animal decomposes and the hard parts of the body become replaced with minerals; this process is called permineralization.

Fossils are often found in sedimentary rock, which is formed by the layering of material over many years. When plants and animals die, they often sink to the bottom of a river or lake, where they are eventually covered over with soil and/or rock particles. Over time these soil and rock layers slowly become pressed together into hard rock, trapping the plant or animal remains between the layers, as fossils.

Because sedimentary rocks form in layers, scientists believe that fossils also form in layers from the oldest fossil to the youngest fossils. So, the fossils at the bottom of a deep layer of rock are most likely the oldest; the fossils toward the top of a rock are most likely the youngest. Scientists call this the "Law of Superposition."

Just as it makes sense that the fossils at the bottom of a rock would be the oldest, it also makes sense that the sediment that covers up organisms (that later become fossils) would be laid down in horizontal layers. This is called the "law of original horizontality." But, we know that over time, these horizontal layers can shift. Sometimes, sedimentary rock layers are not horizontal, but have been moved or shifted due to some change in the Earth.

How do fossils help us learn about the history of the Earth?

Scientists describe the Earth's long history in time periods that compose a geologic time scale. Time periods are broken up into eons, which are further divided into eras, which are then divided into periods, which are then divided into epochs.

Engineers study fossils from all over the geologic time scale. They look closely at the processes and functions that are found in prehistoric nature and apply them to current technologies. By understanding how prehistoric creatures lived and what caused them to become extinct, engineers can get new ideas for how to design something. Engineers can also use this information to create models of global climate change over the life of the Earth, as well as learn more about species extinction.

Engineering Tools

Engineers design the tools that paleontologists use to discover fossils. Examples include:

• Magnetic resonance imaging (MRI): A noninvasive diagnostic technique that produces computerized images of internal body tissues and is based on nuclear magnetic resonance of atoms within the body induced by the application of radio waves.
• Computer-assisted tomography (CAT scan): A medical imaging method in which digital geometry processing generates a 3D image of the internals of an object from a large series of 2D x-ray images taken around a single axis of rotation; used in many fields for nondestructive materials testing, including detecting cracks in aircraft skins, industrial pipes, underground pipes, corroded reinforcing steel inside concrete, leaking welds, finding broken wires in suspension bridges, and forensics, etc.
• Mass spectrometry (or spectroscopy): An instrumental method for identifying the chemical constitution of a substance by means of the separation of gaseous ions according to their differing mass and charge, for identifying unknown compounds to determine physical, chemical or biological properties of compounds.

Lesson Closure

Who can tell me: What is a fossil? A fossil is a remainder of an organism that has been preserved in the Earth. What are different types of fossils? Fossils can be from a plant or animal, and they can even be footprints or droppings. Remember that fossils are formed when an organism dies and is covered in soil, fossilizing the hard parts of the remains. Remember that engineers design creative tools to help us find fossils. They also study fossils to get new ideas. They design technologies to help create physical and chemical images of fossilized organisms. This helps us learn about the physical structure of the organism, the environment that it lived in, the diseases that affected it, and what it used for food. Engineers also use fossils and fossil fuels to create materials and energy that we use every day. So, next time you look at a fossil, think about whether there is any way you can apply what you observed to a current technology!

Vocabulary/Definitions

biomimicry: Copying or imitating the special characteristics of naturally existing things (animals, plants, etc.) in human-made designs, products and systems. From bios, meaning life; and mimesis, meaning to imitate.

body fossil: A fossil of an organism's body.

chemical fossil: Also called biomarkers – a chemical trace of an organism.

engineer: A person who applies his/her understanding of science and math to creating things for the benefit of humanity and our world.

extinct: No longer existing.

fossil: A remainder of an organism that has been preserved in the Earth's crust.

geologic time scale : A scientific method for classifying historical time periods.

macrofossil: A larger fossil specimen, one large enough to be observed by direct inspection.

microfossil: A fossil that can be studied only microscopically, and that may be either a fragment of a larger organism or an entire tiny organism.

paleontologist: A person who studies fossils.

paleontology: The study of fossils.

permineralization: The process whereby groundwater permeates an organism and minerals from the groundwater precipitate out and fill the empty spaces in the body, thus forming a body fossil.

trace fossil: A fossil that shows the activity of an animal or plant but is not formed from the organism itself. A trace fossil shows that an organism was present. Examples: burrows, trails, footprints or droppings.

Assessment

Pre-Lesson Assessment

Discussion Question: Ask students the following question and discuss as a class. First see if students can provide a definition before explaining it to them.

• What is a fossil? (Answer: A remainder of something that lived a long time ago, such as a prehistoric plant or animal.)

Post-Introduction Assessment

Class Vote: Ask several true/false questions about the lesson material and have students vote by holding thumbs up for true and thumbs down for false. Tally the votes and write the totals on the board. Give the right answer. Example questions:

• True or False: A piece of animal droppings (poop) can be a fossil. (Answer: True. This type of fossil is called a trace fossil because it shows that an organism was there.)
• True or False: Fossils are formed when people place them into sand for other people to find later. (Answer: False. Fossils are formed by sedimentary rock being formed on top of and around a dead organism.)
• True or False: Paleontology is the study of fossils. (Answer: True)
• True or False: Engineers have no use for studying fossils. (Answer: False. Engineers can get ideas from studying fossils. They can use what they learn about fossils to design new technologies that mimic the prehistoric natural world.)

Lesson Summary Assessment

Creative Writing: Have each student write an essay or letter from the perspective of a plant or animal that becomes fossilized and then is discovered by an engineer. Have them describe in detail how the plant or animal becomes a fossil, and how they are re-discovered after many years. Then have them explain what they helped the engineer to learn and maybe even a new technology that they influenced the engineer in designing. Award extra points for creativity.

Lesson Extension Activities

Arrange a field trip to a natural history museum so students can see examples of fossils.

If you live near a dinosaur dig or other historical dig area, arrange a field trip to a dig site. With advance reservations, some sites allow students to participate in the dig.

Scientists who study fossils are called paleontologists. Have students research what a paleontologist does and give an oral presentation, "A Day in the Life of a Paleontologist."

Ask students to research magnetic resonance imaging, computer-assisted tomography, and mass spectrometry, reporting back to the class a description of what these tools do for us.

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under grants from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation (GK-12 grant no. 0338326). However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Learning Objectives

After this lesson, students should be able to:

• Explain the connection between tectonic plates and mountain formation.
• Describe several types of technologies designed by engineers that are related to mountain formation, including tools and processes for measuring formation, predicting natural hazards, and determining the location of natural resources.

Worksheets and Attachments

Pre-Req Knowledge

Students should have some familiarity with the existence of tectonic plates, that they move and the various tectonic plate boundaries that exist.

Introduction/Motivation

Did you know that we live on gigantic moving rocks? We call these rocks tectonic plates. They are what make mountain formation possible. What happens when the Earth's 14 major tectonic plates and many minor ones are all moving around? They are bound to start bumping into each other! Natural phenomena such as earthquakes, mountain formation, and volcanoes occur at plate boundaries. Mountains are usually formed at what are called convergent plate boundaries, meaning a boundary at which two plates are moving towards one another. This type of boundary eventually results in a collision. Tectonic plate collisions take a long time, as plates only shift a few centimeters each year, but they can still be powerful enough to form the Earth's largest mountain ranges!

So what happens when the convergent plates finally collide? Well, a few different possibilities can occur. Sometimes, the two tectonic plates press up against each other, causing the land to lift into mountainous forms as the plates continue to collide. Another possibility is that one plate pushes on top of the other, sending it downward into the Earth! We call this a subduction zone. The mountains formed from this powerful compressive process are called complex mountains.

Given these options, how do we know which possibility will occur? It depends on the composition of the tectonic plates involved in the collision. Tectonic plates are either made up of oceanic crust or continental crust. Oceanic crust is mainly made of basaltic rocks, and continental crust is mainly made of felsic rocks. Basaltic rocks are denser than felsic rocks; therefore, oceanic crust is denser than continental crust. So, if an oceanic tectonic plate collides with a continental plate, the denser oceanic plate is likely to sink beneath the continental plate, creating a subduction zone. If, however, two continental plates (therefore of similar density) smack into one another, they, instead, lift up against one another.

Let's look at some diagrams. (By paper handout or overhead projection, show students what happens in the various plate convergence scenarios, as shown in the attached Tectonic Plates Convergence Handout-Overhead.)

Now that we have talked about complex mountains, let's briefly touch on two other types of mountains. Fault-block mountains are formed by an entirely different process. These mountains are produced when tectonic plates are stretched to the point that they crack and slide. These cracks, or vertical faults, are fractures in the continental crust. Crust is then squeezed upward between the two parallel lines, resulting in mountains! And finally, the term erosional mountain describes mountains that are formed due to the erosion of uplifted rocks in the Earth's geography. This process occurs when rivers, over time, carve away at a region of uplifted geography.

But bumps and hills are all over this planet — so what constitutes a mountain? Mountains are landforms that extend above their surrounding areas in a limited area. That is a very general definition! No required elevation exists for a mountain to be called a mountain, so what makes a mountain different from a hill? Mountains are generally considered to be higher and steeper than a hill, but the definitions ultimately depend on local custom. A hill to some is a mountain to others, and visa versa!

Geotechnical engineers study mountains and the movement of tectonic plates for a variety of purposes. They observe plate movements to design technologies to measure the movement of tectonic plates and mountain formation in order to predict earthquakes and how to best protect people from them. Using these technologies, they develop processes and rules for developing communities and roadways around tectonic plate movement (adding extra support requirements to structures on an earthquake fault line). They also use the information to develop technologies that predict locations at which geothermal, oil, natural gas and coal resources may be located. Sometimes geotechnical engineers work with other engineers to turn the geological formations themselves into resources for humans, such as mountain tunnels, dams and roads. After completing the lesson refer to the hands-on associated activity Tunnel Through! to have student teams model the challenges of engineering a tunnel through a mountain for transportation purposes .

Lesson Background and Concepts for Teachers

The Earth's internal structure makes the land and oceans prone to mountain formation. The lithosphere, Earth's rigid top layer of rock, floats on the asthenosphere, Earth's hot, malleable layer beneath the lithosphere. The rigid lithosphere layer is about 100 km (60 miles) thick and makes up the Earth's enormous moving rocks called tectonic plates; 14 major tectonic plates and 38 minor plates are identified. (The Earth's major tectonic plates are the African, Antarctic, Arabian, Australian, Caribbean, Cocos, Eurasian, Indian, Juan de Fuca, Nazca, North American, Pacific, Philippine, and South American Plates.) Tectonic plates are further classified into two major groups based upon their composition: oceanic crust and continental crust. Typically, a single tectonic plate can contain both oceanic and continental crust. Oceanic crust is mainly comprised of basaltic rocks, whereas continental crust is largely made up of felsic rocks, which are lower in density.

Currents acting on the asthenosphere push the Earth's tectonic plates in lateral movements. Because the lithosphere essentially floats on the asthenosphere, movement in the asthenosphere gets transferred to the lithosphere, causing the Earth's tectonic plates to move in different directions. The currents causing this movement in the asthenosphere are not entirely understood, but the Earth's internal heat engine is the hypothesized cause.

Three types of tectonic pl ate boundaries exist: convergent, divergent and transform. Mountains are formed by plate convergence. Plate convergence describes tectonic plate movement that results in the collision of two plates. These slow-moving collisions shift the plates only a few centimeters a year, but are powerful enough to form large mountain ranges over time.

Plate convergence resulting in mountain formation occurs in several ways. First, two tectonic plates can be pressed up against each other until the land lifts and folds over itself. If the two plates involved in the process contain continental crust, it is called a continental collision. Second, one plate can push on top of another, causing the latter to slide downward into the Earth. This is called a subduction zone (when one plate moves underneath the other). At that place, it begins to melt, leading melted rock to escape through cracks and weak spots, and burst out as fiery volcanoes. Third, tectonic plates can stretch until they crack and slide, resulting in fault-block mountains. And finally, underwater mountains are formed when tectonic plates spread away from one another, allowing melted rock to push up through the gap. This process is more common, as mountain formation occurs more often in oceans than on land.

Because mountain peaks experience higher elevations than their surrounding areas, they also experience cold temperatures in higher layers of the atmosphere. Mountains therefore often experience glaciation, when glaciers carve and shape mountain peaks by carrying rocks with them as their ice melts or shifts downward. This process carves sharp horns, rounded bowls, and u-shaped valleys into mountains, creating the images that come to mind when we think about mountains. Mountains can also change shape due to other natural elements such as rain, wind or ice wearing away the rock. Eventually, previously high jagged peaks naturally become low rounded hills and ultimately wear down into soil, sand or sediments.

Lesson Closure

Now that we've talked about mountain formation, describe for me the outer layers of the Earth (Listen and clarify student descriptions). Explain how tectonic plate movement is linked to the formation of mountain ranges. (Listen and clarify student descriptions.) How is this information important to the daily lives of many people? (Listen and add to student answers.) In today's fast-paced world, people who want to get from one side of a mountain to the other prefer the quickest route—driving through! Who are the people responsible for designing tunnels? (Engineers make driving directly through mountains a possibility by designing and constructing mountain tunnels, saving countless travelers, haulers, commuters, emergency vehicles, truckers and vacationers time on the road each day.

Vocabulary/Definitions

asthenosphere: Earth's malleable layer located beneath the lithosphere.

basaltic: Gray to black volcanic rocks.

complex mountains: Mountains formed due to tectonic plates being subjected to large compressive forces.

continental collision: Two plates in motion toward one another cause mountain formation and the collision of two continents.

continental crust: The part of the lithosphere that forms the continents. This material is less dense than oceanic crust, but is considerably thicker.

convergent plates: Two tectonic plates in motion toward one another.

divergent plates: Two tectonic plates in motion away from one another.

fault-block mountains: Mountains formed when continental tectonic plates stretch to the point that they crack and slide.

felsic: Refers to silicate minerals, magmas, and rocks that contain lighter elements such as silica, oxygen, aluminum, sodium and potassium.

lithosphere: Earth's rigid outer layer, consisting of the crust and outermost mantle.

oceanic crust: The part of the lithosphere found in the ocean. This crust is generally composed of mafic basaltic rocks and is denser than continental crust.

subduction zone: When one tectonic plate moves beneath another at a plate boundary. This takes place at convergent plate boundaries if one or both of the tectonic plates at the boundary is made of oceanic crust.

tectonic plates: Large sections that make up the Earth's lithosphere.

transform plates: Two plates that slide and grind against each other in a horizontal direction along a transform fault.

Assessment

Pre-Lesson Assessment

Class Discussion: Ask students what they know about mountain formation to see if they can explain it to you before launching into the lesson.

Post-Introduction Assessment

Class Vote: Give the students several True/False statements about the lesson material and have them vote on whether they think the answers are true or false.

• True or False: The asthenosphere is located below the lithosphere. (Answer: True)
• True or False: The Earth has total tectonic plates. (Answer: False. 14 major tectonic plates, plus numerous [~38] minor ones.)
• True or False: Oceanic crust is denser than continental crust. (Answer: True)
• True or False: Mountains can be formed at convergent plate boundaries. (Answer: True)
• True or False: The lithosphere is Earth's rigid surface layer. (Answer: False. The asthenosphere is Earth's rigid surface layer. The lithosphere is Earth's hot malleable layer located beneath the asthenosphere.)

Lesson Summary Assessment

Student-Generated Questions: Have each student come up with one question to ask the rest of the class on the lesson topic. They should each know the answer to their question! Be prepared to help some students form questions. Have students take turns asking their questions to the class or collect the questions and answers to ask them back to the class in a random order.

Homework

Peak to Peak: Have each student research a mountain range. How was it formed and when? What makes the mountain range unique? Have them present their findings to the class or turn in a written paragraph.

Lesson Extension Activities

If you live near a mountain range, have a geologist take your class on a hike and talk about the formation of your local range and rock composition.

Have students recreate a mountain range using clay and present it to the class. Require their models to be topographically accurate and to scale.

Have students research the Earth's tectonic plates. Are any current movements expected to result in mountain formation?

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under grants from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation (GK-12 grant no. 0338326). However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Learning Objectives

After this lesson, students should be able to:

• Describe several physical properties of soil.
• Describe how soil is formed through the cycling of Earth's materials.
• Explain what a soil profile is and how engineers use it to determine an area's soil quality.

Introduction/Motivation

What is soil? Where does it come from? Soil develops from a parent rock being broken down into small particles over thousands of years due to two major processes: erosion and weathering. Erosion is when rocks disintegrate due to the movement of elements such as water, wind or ice, caused by the flow of energy and the cycling of the Earth's materials. Weathering is when rocks disintegrate simply due to contact with the atmosphere. Both processes can vary greatly by location and over time, resulting in many different types of soils. In other words, many types of soils exist because of differences in parent rock material, climate, topography and time.

What is soil and why is it important? Soil has allowed for the existence of many life forms we know today. It provides plants with a place to grow and meets most of their nutritional needs. Soil that is able to support plant life is made of both organic and inorganic matter. Organic matter is matter that is biological. The soil's organic matter includes materials that are capable of being decayed, like decomposing plants and the remains of once-living organisms. Inorganic matter is matter that comes from mineral. Inorganic matter in soil includes things such as weathered rock and minerals, as well as air and water. An average soil consists of about 95% inorganic matter and 5% organic matter.

Of the 5% organic matter found in average soil, 80% of that organic matter is in the form of humus (with another 10% as roots and 10% as organisms). Humus is a dark brown or black substance naturally found in the soil. So where does humus come from? Organisms living in the soil naturally add organic matter to their surroundings, and when fungi and bacteria decompose, this organic matter, humus is formed. Larger organisms, such as earthworms, later spread the humus into deeper layers, further developing the soil and making it possible for plants to grow.

Have you ever taken a closer look at soil? Is it the same (homogenous) throughout? Erosion, decomposition and weathering all contribute to soil naturally developing in layers. If you looked at a cross-section of some soil in the ground (when you look at a side view) you might see at least three horizontal layers: the topsoil, sub-soil and bedrock. We call this cross-section view a soil profile. The topsoil is the dark top layer of soil that extends 15 to 20 cm below the surface of the Earth. Air, water and humus are present in the topsoil, helping plants to grow in this layer. The sub-soil layer is found below the topsoil, and has many clay-like characteristics; it acts as a reservoir for storing water that plants need. Below the sub-soil is bedrock. Bedrock is sometimes referred to as parent material because both the topsoil and sub-soil originate from the rocks that make up the bedrock.

Geotechnical engineering is a branch of civil engineering that works with rocks, soils and Earth materials. To make recommendations for building on a specific piece of land, geotechnical engineers first take a look at the surface and subsurface conditions of an area. The engineers might draw a soil profile during a site assessment. Site assessments are investigations of the Earth that take place before some other engineering is performed, such as designing a community of houses or even a research area in a wilderness park. The engineers must find out what types of soils and rock they are working with before they spend the money to design and build something on top of it. Geotechnical engineers look at many soil properties when conducting site investigations. They may look at color, types of mineral present, material weight, porosity (or how much air is in the soil), permeability of the soil (how much water can flow through it), and how much stress or force the soil can undergo without changing.

Besides building large structures or fixing existing structures that are falling down, other reasons exist for why engineers might investigate the soil in an area. Environmental engineers look at soils to determine the health of the area. They may take several soil samples to determine where a toxic contaminant spill is located that is affecting the health of the people in the community. They may also use soil samples to follow the path of water or pollution through the ground, or to search for specific minerals or fossil fuels. Agricultural engineers study soil samples to determine how to help crops grow better.  Other engineers investigate soils to see how they are changing and how the change effects threatened wildlife and plant species. Students can act as engineers in the associated activity Soil Core Sampling where they learn more about the benefits and steps of soil sampling. Soils are very important to life on Earth and engineers help us protect those soils and decide where to best grow our communities without destroying the healthy soil.

Lesson Background and Concepts for Teachers

Additional Soil Information

The different processes that determine the properties of soil (as well as minerals and rocks) are the result of the flow of the Earth's energy and the cycling of materials. The energy that drives these processes comes from the sun and the Earth's interior. Weathering is one process that results from this cycle and drives the changes in Earth's materials and organisms. Specifically, two main types of weathering affect the components of soil: physical and chemical. Physical weathering describes the breakdown of rocks and soils due to atmospheric conditions, such as temperature, water or pressure. Chemical weathering describes the impact of chemicals (either produced biologically or by the atmosphere) on the breakdown of rocks and soils.

Humus enables soil to hold more moisture and provides plants with their primary source of carbon and nitrogen, all of which benefit soil by making it better at supporting plant growth. To understand humus, it would be helpful to look at it, but it is difficult to see humus alone because it is bound to larger particles in the soil.

Plant roots located in deeper layers of the soil require air and water for growth and survival. Air and water is present in the topsoil, but must be transferred to the deeper layers by mixing and aeration. This process can occur naturally with the help of earthworms and other insects. Earthworms that spread humus to deeper layers of soil are also paramount in mixing and aeration. In fact, these two phenomena are closely related. The term translocation describes the process in which water moving through soil simultaneously causes other materials in the soil (such as humus) to move and spread.

Various environmental factors impact the color of soil in both the horizontal and vertical directions. For example, a soil that contains more humus is darker than one with a more moderate amount. Iron and aluminum in some soils undergo chemical reactions that cause the soil to turn shades of red and yellow. Many additional coloring materials are found in soils.

Lesson Closure

Now that you have learned the basics about soil, explain to me what soil is and how it is formed. (Listen to student descriptions.) Soil is able to support plant life; it is made up of both organic and inorganic matter. The three main horizontal layers of soil are: the topsoil, sub-soil and bedrock. Most of the soil we see is topsoil. Topsoil contains amounts of air, water and humus and is a good place for plants to grow.

Geotechnical engineering is a type of civil engineering that specializes in understanding rocks, soils and Earth materials. These engineers take soil samples and create soil profiles to determine if an area is good for the placing a building or structure. Environmental engineers look at soil samples to determine if pollution is in the soil, the effects of developments on soil, or the location of minerals and fossil fuels. They look carefully to see if the changes in soil affect the plants and animals that live in the area. Agricultural engineers study soil samples to make recommendations for growing crops. Soil is an important part of life and engineers help us use the soil to learn about our impact on the Earth.

Vocabulary/Definitions

chemical weathering: The disintegration of rocks and soils due to chemicals produced biologically or by the atmosphere.

erosion: The disintegration of rocks and soils due to wind, water, ice or other processes. This process occurs with movement.

horizons: Layers of a soil profile.

inorganic matter: Materials that originate from mineral sources.

leaching: The process of extracting a substance.

organic matter: Materials of biological origin that are capable of being decayed.

physical weathering: The disintegration of rocks and soils due to atmospheric conditions such as heat, water or pressure.

soil profile: A cross-section through the soil. This side-view angle shows a soil's layers.

translocation: When water moves through soil causing materials in the soil to move and spread.

weathering: The disintegration of rocks and soils due to contact with the atmosphere. This process occurs without movement.

Assessment

Pre-Lesson Assessment

Brainstorming: In small groups, have students engage in open discussion. Remind them that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Encourage wild ideas and discourage criticism of ideas. Ask the students:

• What is soil?
• From where does it come?
• What processes form soil?

Post-Introduction Assessment

Drawings: Have students draw a cross-section view of a soil sample. Direct them to label the soil layers and incorporate symbols of what might be found in that layer. For example, draw plants and roots, or use little As for air or Ws for water. Communicate the differences between the soil layers with color or fill patterns to show density of the soil layer. Have students also incorporate what processes could have contributed to the formation of their soil by drawing arrows and labeling possible explanations. Have students estimate what percent each layer makes up the whole. Students should write a percentage next to the soil layer and be able to give an explanation as to why they believe that layer takes up that percentage. Have students explain their soil profiles and the relationship to material cycling and weathering processes to other students in the class.

Lesson Summary Assessment

Soil Investigation: Have students think about the soil in either your area or one that you assign. What is the climate like? How does that affect the topsoil? How does the soil compare to the soil in other parts of the world? If they were geotechnical engineers, what types of things might they communicate about the soil in their areas?

Lesson Extension Activities

As an extension, consider teaching A Good Foundation lesson and Shallow and Deep Foundations activity in the Bridges unit, in which students explore the effects of regional geology on bridge foundation, including the variety of soil conditions found beneath foundations. They learn about shallow and deep foundations, as well as the concepts of soil profiles, bearing pressure and settlement.

See the Natural Resources Conservation Service webpage with several hands-on lesson extension options: http://soil.gsfc.nasa.gov/

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under grants from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation (GK-12 grant no. 0338326). However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.