The Critical Zone

Lesson Overview


In this lesson, we will focus on soil, the "heart" of the Critical Zone. I am not concerned that you memorize various definitions for soil—instead, I want you to learn that soil consists of mineral and organic matter derived from a variety of sources and that it is vitally important to sustaining life on Earth, including human society. To do this we will examine the basic processes involved in soil formation (the so-called state factors of soil formation), simple scientific approaches to studying and classifying soils, and the global distribution of different types of soils (soil orders). You will learn that soils are not randomly distributed on our planet, but instead, occupy space determined by the overlapping domains of the state factors of soil formation. Ultimately, soil records the overlap of atmospheric, lithospheric, hydrologic, and biologic processes, the innermost workings of the Critical Zone. Finally, you will consider the distribution of soils near your workplace and the implications of the distribution to understanding Critical Zone processes and land use at the site. You will accomplish this by using an online resource that you may want to introduce into your own classroom. In a later lesson, we will apply this knowledge of present-day soils to learn about ancient soils (paleosols) and their importance for understanding Earth history and perhaps Earth's future.

What will we learn about in Lesson 2?

  • What is soil? How does it form? How is soil studied and classified?
  • The importance of soil—why should we care?
  • How is soil geographically distributed?
  • What are the threats to soil?
  • How are soils mapped and how can you determine soil types in any region of the United States?

Learning Objectives

By the end of this lesson you should be able to:

  • describe soil as a societally relevant mineral and biotic entity
  • list the five state factors of soil formation and basic information regarding the importance of each
  • discuss how soils are described and classified into twelve soil orders and how those soil orders are geographically distributed
  • list five of the major threats to healthy soils
  • explain the use of information from the Web Soil Survey and how it can be applied to land-use planning and decision making

What is due for Lesson 2?

Lesson 2 will take us one week to complete. As you work your way through these online materials for Lesson 2, you will encounter additional reading assignments and hands-on exercises and activities. The chart below provides an overview of the requirements for Lesson 2. For assignment details, refer to the lesson page noted.

Please refer to the Calendar in Canvas for specific time frames and due dates.

Lesson 2 Activities
Answer questions about soil erosion page 3 Upload your responses to the Lesson 2 - Soil Erosion dropbox in Canvas
Answer questions about soil orders page 6 Upload your responses to the Lesson 2 - Soil Orders dropbox in Canvas
Short report on the Web Soil Survey page 7 Upload your report to the Lesson 2 - Soil Survey dropbox in Canvas
Discussion—Teaching and Learning About Soil page 9 Participate in the Unit 2 - Teaching and Learning About Soil discussion forum in Canvas


If you have any questions, please post them to our Questions? discussion forum (not e-mail), located under the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate.