The Critical Zone

Lesson Overview


The geology of a region controls the parent material available for pedogenesis. Parent material can be represented by a wide range of rock types of varying geochemical compositions, it can be lithified (hardened) or unconsolidated, and it can be relatively recent in age or billions of years old. The geologic setting of a region, past and present, also determines whether or not mountains or valleys exist, thereby exerting a first-order influence on the topographic setting in which Critical Zone processes function and soils form. Furthermore, the geologic setting will determine whether parent material lies within an active setting, perhaps only recently exposed to pedogenic processes; or within a more stable setting in which soil formation may continue unabated, subject only to the vagaries of climatic and biotic change.

What will we learn about in Lesson 8?

  • Basic geologic concepts
  • Rock types and the rock cycle
  • Plate tectonics
  • Geologic time
  • Weathering, erosion, and deposition
  • Geologic maps

Learning Objectives

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

  • Describe three rock types and the processes by which they form
  • Discuss the rock cycle and plate tectonics
  • Differentiate between relative and absolute age dating
  • Describe the difference between weathering and erosion and their relationship to soils
  • Differentiate between bedrock and surficial geologic maps and apply them to understanding the Critical Zone at your study site

What is due for Lesson 8?

Lesson 8 will take us one week to complete. As you work your way through these online materials for Lesson 8, you will encounter additional reading assignments and hands-on exercises and activities. The chart below provides an overview of the requirements for Lesson 8. For assignment details, refer to the lesson page noted.

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

Lesson 8 Activities
Report (2 pages) on parent material questions pages 4, 7 Post to the Lesson 8 - Geology dropbox in Canvas
Report (2 pages) with relevant maps page 8 Post to the Lesson 8 - Geologic Map dropbox 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.