Lesson: Earth Rocks!

Contributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

A translucent purple amethyst crystal.
Figure 1. A picture of an amethyst crystal. Amethyst is a type of quartz and is a mineral that is found in the Earth.
Copyright © U.S. Geological Survey and the Mineral Information Institute, http://resourcescommittee.house.gov/ subcommittees/emr/usgsweb/ photogallery/


The purpose of this lesson is to introduce students to the basic elements of our Earth's crust: rocks, soils and minerals. They learn how we categorize rocks, soils and minerals and how they are literally the foundation for our civilization. Students also explore how engineers use rocks, soils and minerals to create the buildings, roads, vehicles, electronics, chemicals, and other objects we use to enhance our lives.

Engineering Connection

Engineers care about rocks, soils and minerals. One reason they are important is that they are the foundation for our buildings and roads. Engineers also get many of the materials they use for construction from rocks, soils, and minerals. Engineers must understand the properties of these rocks, soils, and minerals so that they can use the ideal material for a job that is efficient and cost effective.

Learning Objectives

After this lesson, students should be able to:

  • Describe the difference betweens rocks, soils and minerals.
  • Explain that engineers use rocks, soils and minerals for constructing and manufacturing.

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  • Identify evidence from patterns in rock formations and fossils in rock layers to support an explanation for changes in a landscape over time. (Grade 4) Details... View more aligned curriculum... Do you agree with this alignment?
  • Analyze and interpret observations about matter as it freezes and melts, and boils and condenses (Grade 3) Details... View more aligned curriculum... Do you agree with this alignment?
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What is the Earth made of? What is the "stuff" near the surface of the earth made of? (Lead the students to answers such as rocks, boulders, pebbles, dirt, soil, metals, gems, minerals, etc.) These are the materials that make up the ground we walk on. It is what holds together lakes, rivers and oceans. It is where plants grow and where we build our roads, buildings and parks. We build tunnels through it, and we build bridges over it. These materials are collectively known as rocks, soils and minerals. These three materials are the main component of our Earth's crust, and they are the foundation on which we build our civilization.

What is the difference between rocks, soils and minerals? (Make a chart on the board with three columns, labeled "Rocks," "Soils" and "Minerals." Ask students to fill in any characteristics they can think of in each column.) Minerals are non-living things and have a definite crystal-like structure. This means that they do not come from plants and animals and have a definite shape, such as square or an octagon. An example of a mineral is salt. Have you ever looked at salt closely? Did you notice that each individual grain has a shape to it? Salt is an example of a mineral. Rocks are usually several minerals stuck together. In fact, it is easier to find a mineral (embedded) in a rock than on its own. Rocks can also contain other things, like fossilized plants or animals. Rocks are labeled by how they were formed. There are three types of rocks: sedimentary, igneous and metamorphic. Lastly, soils are collections of very small pieces of rocks that were broken down over time. Soils often contain other things as well, like decaying plant pieces. Soils are typically identified by texture and how large the particles in the soil are. There are three different textures of soil: sand, silt and clay.

There are lots of other important uses for rocks, soils and minerals. Can you think of what they might be? We use rocks, soils and minerals to construct a lot of the things we use on a daily basis. Some of the materials we use that are actually considered rock, soils or minerals include metals (steel, gold, copper, silver, aluminum, etc), concrete, ceramic, clay, sand, gems (diamonds, emeralds, rubies, etc), salt, drywall and glass. Engineers use these materials when creating everything from buildings, to roads, to cars, to cell phones, to computers, to medicines. Rocks, soils and minerals are incredibly important to us in our daily lives. Today, we are going to learn more about rocks, soils and minerals and how engineers use them in everyday life.

Lesson Background and Concepts for Teachers

The crust of the Earth, where all plants and animals live, is composed of many different rocks, soils and minerals. Engineers care a great deal about rocks, soils and minerals since we build structures upon them, and, very importantly, they are the source for most of our building materials. These rocks, soils and minerals provide the landscape, a place for our food to grow, and the ground on which we build our roads and buildings. They also are the sources of building supplies we use to make everything from computers, to roads, to bicycles, to buildings, and even toilets! Even things such as oil, which are used to make plastics, only form because of the weight of the rocks and soils above oil deposits. Other materials we use grow in the Earth's soils, such as wood and certain medicines.

The basic component in both rocks and soils are minerals. Minerals are solid inorganic compounds (not from living material, such as plants or animals) that have a definite chemical composition and a crystalline structure. A common example of a mineral is salt. Salt has a definite chemical composition (Sodium Chloride or NaCl) and has a crystalline structure. Some other examples of minerals include: quartz, mica, calcite, gypsum (used to make dry wall), hematite (iron ore), gold, silver, aluminum, copper ─ and, even ice is a mineral. In the Earth's crust, we usually do not find minerals alone in their pure form. Minerals are typically mixed with other minerals, so if we want to use just one particular mineral we may have to separate it from other minerals first.

Rocks are actually aggregates of two or more minerals. In fact, minerals are more often found in rocks as opposed to being alone in their pure form. The mineral iron is usually found in a rock known as an ore that contains iron, but is mixed with other minerals. Rocks can also contain organic materials such as fossilized plants or animals. Rocks are categorized by how they were originally formed. There are three types of rocks: sedimentary, igneous and metamorphic. Sedimentary rocks are formed by sediments ─ soils that are deposited by water or wind. These soils (sediments) get compacted over time and eventually cement to form a solid rock. Examples of sedimentary rocks include sandstone, limestone and shale. Igneous rocks are formed from the liquid rock in the center of the Earth ─ known as magma. As magma cools and hardens, igneous rocks are formed. Examples of igneous rock include granite and obsidian. Metamorphic rocks are formed when the high temperatures and pressures below the surface of the Earth changes the structure of a sedimentary, igneous or other metamorphic rock. Examples of the metamorphic rocks include gneiss, schist and marble. Engineers use rocks when building roads. They also mix rocks with cement to form concrete, which is used for many construction projects.

The image shows a poster graphic about the rock cycle and how rocks are always changing. It shows how the rock cycle moves through stages of sedimentary, heat and pressure, metamorphic, melting, and igneous.
Copyright © http://www.mapstore.utah.gov

Soils are collections of very small pieces of rock that have been broken down ─ over the course of many (many) years ─ by erosion. Soil often contains organic material from decaying plant material. There are many different ways to categorize soils. Soils are typically organized by texture. This is related to the size (how large) of the particles in the soil. The three different textures of soil are: sand, silt and clay. Sand is the coarsest type of soil. Sand particles feel rough because they are sharp and large. Silt particles are smaller than sand particles, and because of this, silt feels smooth. Clay particles are the finest form of soil. Clay is very smooth and becomes very sticky when it is wet.

Rocks, soils and minerals are very important to engineers. So much of what engineers use to build "things" comes from rocks, soils and minerals. Minerals are especially important, as they (i.e., especially metals) are used to construct cars, planes, trains, buildings and bridges. Metals and other minerals such as silicon are the primary components of electronics, such as computers, cell phones, digital cameras and televisions. Chemical engineers use minerals when creating new chemicals, including various life-saving and preventative medicines. Rocks and soils are also used extensively by civil engineers in construction projects, and metals and concrete have become the building materials of choice. Concrete is made from limestone, clay, water and aggregate (usually gravel), and it is often used in the construction of bridges, roads, tunnels, dams and large buildings. Environmental engineers also care about rocks, soils and minerals because they use materials such as sand as water filters as well as study soils to see how water and pollutants move through them. Rocks, soils and minerals are very important to us as they make up many of the objects around us as well as where we build the buildings and roads that are the foundation for our civilization.

Case Study: The Grand Canyon

The image shows is a diagram showing the three sets of rocks that make up the Grand Canyon. These include Layered Paleozoic Rocks, Grand Canyon Supergroup Rocks, and Vishnu Basement Rocks.
Figure 1: Grand Canyon's Three Sets of Rocks
Copyright © http://www.nature.nps.gov/geology

We can see in Figure 1 that the oldest rock formations are at the bottom, and the youngest on top. We can also observe that the schists and gneiss (metamorphic), as well as granite (igneous), lie at the bottom as well. These types of rock, in particular metamorphic, are formed at high pressures and temperatures (from the weight of rock and soil above, as well as the heat from the earth's core). Near the top of the Grand Canyon is sedimentary rock, including shale, limestone, and sandstone. These patterns suggest geological changes over time, including the formation of rock from magma (igneous), the transformation of this igneous (or sedimentary) rock under pressure and temperature to metamorphic rocks, as well as the erosion of layers through wind and water (the Colorado River).


igneous : Rocks that formed from liquid magma.

metamorphic: Rocks formed when an igneous, sedimentary or metamorphic rock is altered by the heat and pressure deep within the Earth.

sand: Large soil particles that feel rough; sand drains water very well.

sedimentary: Rocks that are formed when soil deposit become compacted over time and eventually cement.

silt : Soil particles that are smaller than sand, but larger than clay; silt is smooth, but does not become sticky when wet.

Associated Activities

Lesson Closure

Can you think of some examples of minerals? (Possible answers: salt, gold, iron, copper, gypsum, etc.) Do we usually find minerals alone? No, usually we find minerals mixed with other minerals. These mixed up minerals in large solid form are known as rocks. Do you know what it is called when the rocks break down into lots of very small pieces? Well, these small pieces are collectively known as soil. What are the three types of soil? They are sand, silt, and clay. How do engineers use rocks, soils and minerals on a daily basis? Well, we learned that engineers use rocks, soils and minerals when they design buildings, roads, foundations, electronics, bridges, cars, appliances and all sorts of other things.


Pre-Lesson Assessment

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

  • Who thinks windows are made out of soil? (Answer: True, windows are made out of glass, which is made from sand, which is a type of soil.)
  • Are there different layers of rock and soil? Have you seen this in real life? (Answer: True. Some students may recall seeing layers of rock in a nearby canyon or mountain. Also, soil layers should be evidenct in many different locations.)
  • Has the rock and soil of Earth remained the same forever? (Answer: False. Changes over time affect mountains, canyons, and landscapes of all types, specifically soil and rock patterns. As seen in the Grand Canyon (Figure 1), each layer of rock took millions of years to form. Although the Earth is constantly shifting, we cannot observe most of the changes due to their very long time scale.)

Post-Introduction Assessment

One and Done: Have the students try and name things they use on a daily basis that comes from a rock, soil or mineral, and raise their hands (or indicate thumbs up) when they have an example. Call on students at random to state their answer. Students put their hands down once they have contributed an answer. No repeat answers permitted.

You might have to prompt them to get some responses. Answers might include.

  1. Bicycle (steel – mineral)
  2. Pencil lead (graphite – mineral)
  3. Asphalt road (has rocks mixed in)
  4. Chalk (calcite)
  5. Mirror (glass – sand – soil; aluminum or silver – mineral)
  6. Light bulbs (tungsten, glass and iron)
  7. Anything metal
  • Spoon/knife/fork
  • Pencil sharpener
  • Chair or desk
  • School bus
  • Coins
  1. Anything electronic (contains metals and other minerals such as quartz and silicon)
  • Watch
  • TV
  • Microwave
  • Computer
  • Game boy
  • CD player
  1. Anything ceramic (comes from clay – soil)
  • Plate/bowl
  • Tea cup
  • Bathroom sink, toilet and bathtub (bathtub may be metal as well)
  1. Anything concrete (has rocks and cement which comes from limestone)
  • Building
  • Bridge
  • Sidewalk

Lesson Summary Assessment

Engineering Class Discussion: Have the students discuss why we use certain materials for certain jobs. Why don't we use concrete for airplanes? Why don't we build pencils out of sand? Why don't we build windows out of clay? Why don't we build schools out of diamonds? The students should realize that the properties of the material dictate what we use and where we use it. When building, engineers must pick the correct rocks, soils and minerals so that their design will work, is safe and is not too expensive.

Lesson Extension Activities

Have the students research different minerals and investigate their uses. Have each student pick one mineral and write a paragraph about the mineral and how engineers use that mineral. Visit the U.S. Geological Survey and the Mineral Information Institute's webpage on "Minerals in Your World" for some examples: http://naturalresources.house.gov/


Trakhtenberg, Izolda. National Aeronautics and Space Administration, Goddard Space Flight Center, "Soil Science Education Homepage," National Science Foundation, Grant No. 9801747, April 20, 2005, http://soil.gsfc.nasa.gov/ Accessed June 13, 2006.
U.S. Department of the Interior, U.S. Geological Survey, Science Topics – Earth Characteristics, "Rocks and Deposits," March 17, 2006, http://www.usgs.gov/science/science.php?term=1005 Accessed June 13, 2006.
Wikimedia Foundation, Inc., Wikipedia, the Free Encyclopedia, "Geology," http://en.wikipedia.org/wiki/Geology Accessed June 13, 2006.


Geoffrey Hill; Malinda Schaefer Zarske; Janet Yowell


© 2006 by Regents of the University of Colorado.

Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder


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.