As introduced in Lesson 1, Critical Zone processes are represented by coupled physical, biological, and chemical processes that involve study by experts in geology, soil science, biology, ecology, geochemistry, geomorphology, and hydrology, to name a few of the relevant sciences. While these various disciplines are equally important for understanding the Critical Zone, they are linked by the presence of soil, considered by many to be the central component of the Critical Zone. This concept is perhaps best illustrated by the SoilCritZone logo shown here: a four-leaf clover-like emblem of yellow (at top, representing atmosphere), green (right, biosphere), blue (left, hydrosphere), and brown (bottom, lithosphere) arcs surrounding the acronym SoilCritZone; the design of the logo symbolizes how soil and the Critical Zone exist within the overlapping region between the four arcs or "spheres." The spheres closely overlap with the state factors of soil formation you will be introduced to later in this lesson: parent material, climate, topography, biota, and age.
Many of you may consider soil to be the mud you played in as a child, the material into which you plant your garden or the dirt you scrape off the bottom of your shoes or wipe from your dog's muddy feet. To most of humanity, soil may even seem to be a nuisance—the word itself has various meanings depending on the usage: as a verb, soil means to make dirty; to disgrace or tarnish; to corrupt or defile; or to dirty with excrement (Free Online Dictionary [1]).
To begin to focus your attention on the positive aspects of soil, please consider the following four definitions. Soil is:
Though the four definitions share common attributes, they do differ. For example, agronomists and most soil scientists focus their studies of soil on the rooted zone, or rhizosphere (approximately to depths of one meter), while the geologist's perspective is much broader and deeper, encompassing the full thickness of material down to the original parent material (shallow to depths up to one hundred meters or more). Nonetheless, most scientists agree that soil is a complex biomaterial that promotes the growth of terrestrial organisms, that it is crucial to life on Earth, and that it is the product of material derived from weathering of parent material, decomposing plant matter, and atmospheric deposition. Furthermore, as soil resources are finite, humanity should view them as non-sustainable and learn to care for and sustain these important resources. For these reasons, we will now turn our attention in Lesson 2 to the study of soil, the "heart" of the Critical Zone.
Browse the following Web site to learn how a consortium of university and government agencies from the European Union focused on Critical Zone studies in Europe and d information to guide the development of better government policies to sustain soil resources.
(Optional) Visit the U.S. Department of Agriculture Soil Resource Management [3] research program's Web site to learn about soil conservation and management, nutrient management, soil water and biology, and other soil-related research in the U.S.
Also, check Soil Education [4] for a wide range of important information regarding soils, including various media that can be introduced into your classrooms.
The Smithsonian's National Museum of Natural History has recognized the societal importance of soil by creating an exhibit that opened in Summer 2008. To learn more about this exhibit, see Dig It! The Secrets of Soil [5]. Be sure to view the new curator-led tour of the exhibit.
Finally, you may also be interested in this beautiful informative brochure [6] created by the Swiss National Science Foundation, in part to observe the 2015 International Year of Soils.
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.
By the end of this lesson you should be able to:
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.
ACTIVITY | LOCATION | SUBMISSION INFORMATION |
---|---|---|
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.
Much of Earth's surface is covered by unconsolidated debris overlying hard, unaltered rock. This unconsolidated layer is called regolith. The regolith may have formed in place immediately above unaltered rock, or may have been transported by various physical processes we will discuss in Unit 4. Soil is derived from the physical, chemical, and biological alteration of regolith.
At the simplest level, the presence or absence of soil can be considered as dependent upon whether alteration of regolith (soil formation) occurs faster than soil erosion. Soil erosion occurs naturally but is widely recognized to have been greatly increased by human activities in the Critical Zone—both the natural and human-influenced (or anthropogenic) rates of soil erosion have been well studied and measured.
For this assignment, you will need to record your work on a word processing document. Your work must be submitted in Word (.doc) or PDF (.pdf) format so I can open it. In addition, documents must be double-spaced and typed in 12 point Times Roman font.
L2_soilerosion_AccessAccountID_LastName.doc (or .pdf).
For example, student Elvis Aaron Presley's file would be named "L2_soilerosion_eap1_presley.doc"—this naming convention is important, as it will help me make sure I match each submission up with the right student!
Upload your paper to the "Lesson 2 - Soil Erosion" dropbox (see the lesson folder under the Modules tab) by the due date indicated on our Canvas calendar.
You will be graded on the quality of your writing. You should not simply write responses to the questions and submit them to me. Instead, plan on writing a short stand-alone paragraph (or page or whatever you decide is necessary considering any constraints I might have placed on you) so that anyone can read what you've written and understood it. You should strive to be specific and complete in responding to the questions. Your answers should be analytic, thoughtful, insightful, and should provide connections between ideas. The writing should be tight and crisp with varied sentence structure and a serious, professional tone.
Soil formation, or pedogenesis, typically happens over long periods of time. The so-called "mineral" component of soil is formed from the weathering, or decomposition, of rocks and minerals. There are two types of weathering: physical and chemical. Physical weathering involves the breakdown of rocks into smaller particles through direct contact with atmospheric heat, moisture, and pressure. The effects of various chemical processes (e.g., atmospheric or biologic) on the size and composition of minerals and rock is known as chemical weathering. Weathering processes will be further explored in our landforms unit.
The rates of soil formation have not been as well characterized as soil erosion rates. This creates an interesting conundrum for scientists and land-use planners interested in the impacts of soil erosion. Though we know there are sites on Earth where soil is eroding at an unsustainable rate, do sites exist where soil is forming at a rate that equals or exceeds the rate of soil erosion? If so, soil erosion may not be an important consideration for these sites when considering land-use issues. Therefore, accurate determinations of soil formation rates under varying conditions are a key question in Critical Zone science.
Soil formation is controlled by five variables in nature. Those variables are:
In addition, most scientists also recognize that humanity, having influenced much of the Critical Zone, represents a sixth factor in soil formation. The varying distribution of these variables in soil formation (also known as the state factors) on Earth's surface, and therefore the differing distribution of physical, chemical, and biological processes dependent upon the distribution and interplay of the state factors, plays a role in soil formation and the development of different types of soil.
Before we progress to learn about the different soil types and their distribution on Earth, I want you to first understand the state factors of soil formation. Please read the following text chapter, which is available through Library Resources:
As you read this, keep in mind that I'd like you to leave this reading assignment able to list the state factors of soil formation. You should also understand the basics of the role each state factor plays in soil formation. Begin to think about the varying distribution of the state factors on a landscape-versus-global scale. Do you think patterns exist in the distribution of the state factors? If so, do these patterns carry over to observable patterns in the distribution of the soil orders?
Soils are characterized in the field in natural exposures, in dug soil pits, or in places where augers can be used to bore holes and obtain samples from the subsurface. Typically soils are described on the basis of the presence of soil horizons and the character of the boundaries between horizons, the texture of the soil based on the size of the soil constituents, the color of the soil material, the structure of the soil, the presence of organic matter and roots, and the hydraulic conductivity. Other relevant characteristics include the geomorphic (landscape) location of the soil (including slope, elevation, aspect), and soil parent material. These characteristics are in turn used to classify soils—we will discuss the classification of soils to the order level, that is twelve soil orders. Before we do, follow each of the links below to learn more about soil sampling and characterization.
You will notice that there is a substantial overlap between the first Weblink shown below and the following four Weblinks. I would like you to visit all of these Web sites but spend no more than two hours total reviewing this information.
Different soil types are variably distributed across Earth's continents, dependent upon the varying relative influence of the state factors of soil formation. These varying soil types are recognized by the characteristics you studied when considering soil description and classification. The various soil types are mappable units; that is, they exist as coherent bodies of similar soil material which eventually merge laterally with other soil types, bedrock, or unaltered sediment. The process by which the distribution of the different soil types are mapped in the field is called soil surveying or soil mapping [22].
The term "soil survey" is also used to describe the published results of soil mapping efforts. Typically these published reports include information about slope, permeability, and drainage characteristics, to name a few and are therefore very important reference manuals in land-use planning and decision making. In the United States, we are fortunate to have a Federal agency which oversees soil mapping, currently named the Natural Resources Conservation Service (NRCS).
For this assignment, you will need to record your work on a word processing document. Your work must be submitted in Word (.doc) or PDF (.pdf) format so I can open it. In addition, documents must be double-spaced and typed in 12 point Times Roman font.
You will be graded on the quality of your writing. You should not simply write responses to the questions and submit them to me. Instead plan on writing a short stand-alone paragraph (or page or whatever you decide is necessary considering any constraints I might have placed on you) so that anyone can read what you've written and understood it. You should strive to be specific and complete in responding to the questions. Your answers should be analytic, thoughtful and insightful, and should provide an insightful connection between ideas. The writing should be tight and crisp with varied sentence structure and a serious, professional tone.
A wide range of soil classification schemes has been developed by various nations primarily interested in the agricultural aspects of their native soils. Again, you should not spend much more than two hours reviewing this information.
"Teacher's Domain" is a free resource, but you must register with them in order to view more than seven resources. Since we'll point to that resource throughout this course, you may want to take a moment to go ahead and register with them now.
L2_soilorders_AccessAccountID_LastName.doc (or .pdf).
For example, student Elvis Aaron Presley's file would be named "L2_soilorders_eap1_presley.doc"—this naming convention is important, as it will help me make sure I match each submission up with the right student!
You will be graded on the quality of your writing. You should not simply write responses to the questions and submit them to me. Instead plan on writing a short stand-alone paragraph (or page or whatever you decide is necessary considering any constraints I might have placed on you) so that anyone can read what you've written and understood it. You should strive to be specific and complete in responding to the questions. Your answers should be analytic, thoughtful and insightful, and should provide an insightful connection between ideas. The writing should be tight and crisp with varied sentence structure and a serious, professional tone.
(Optional) Visit the United States Department of Agriculture (USDA Website [28]).
Soils provide a number of essential goods and services to humanity, including biomass and food production, water filtration, carbon sequestration, and the substrate on which we live our daily lives. Yet the actions of human society present the single largest threat to this essential component of the Critical Zone and Earth system. Negative impacts to soils from human activity include erosion, compaction, salinization, sealing by paving, pollution, and declines in organic matter content and biodiversity. To learn more about threats to soil, visit The Environmental Literacy Council [30]. As you read the short statement there, think about how your own actions threaten the health of soil in your yard, community, and nation. Do you apply herbicides and pesticides to maintain a weed- and pest-free lawn? Do you have a paved rather than gravel driveway? If you have a septic system, do you maintain it and is it operating properly? Do you purchase food grown locally using sustainable agricultural practices? These are just a few of the actions you may take in your lives that preserve the health of soils.
Let's take some time to reflect on what we've covered in this unit!
For this activity, I want you to reflect on what we've covered in this unit and to consider how you might adapt these materials to your own classroom. Since this is a discussion activity, you will need to enter the discussion forum more than once in order to read and respond to others' postings.
You will be graded on the quality of your participation. See the grading rubric [31] for specifics on how this assignment will be graded.
In this lesson on soils, you read about soil formation, the description of soils, and the classification of soils in the United States into twelve soil orders. You also considered the effects of soil erosion on the Critical Zone and how the distribution of the twelve soil orders might relate to the five state factors of soil formation. By now you should understand that soil is a complex material composed of mineral and organic matter, formed by competing processes associated with climate, biota, parent material, topography and time. Soil exists in the overlapping realm between the atmosphere, hydrosphere, lithosphere, and biosphere. It is classified according to need: a geologist studying soil formation rates may have a very different view of soil compared to an engineer building a superhighway or an agronomist trying to understand soil fertility for crop management. Furthermore, due to the increase in human activity on Earth, soil erosion mostly exceeds soil formation rates, thus soil should be viewed as a finite resource that is rapidly being depleted. Finally, you should be well aware that soil maps are available for most of the United States and that they can be very useful, if not critical, for land-use planning and decision making.
With this firm background, throughout the course I want you to remember and contemplate the outstanding question in Critical Zone science, which was introduced in a Lesson 1 reading (Brantley et al. p. 11): can a unified approach be developed to characterize environmental conditions and mechanisms that produce different soil types?
You have finished Lesson 2. Double-check the list of requirements on the Lesson 2 Overview page to make sure you have completed all of the activities listed there before beginning the next lesson.
If you have anything you'd like to comment on or add to, the lesson materials, feel free to share your thoughts with Tim. For example, what did you have the most trouble with in this lesson? Was there anything useful here that you'd like to try in your own classroom?
Links
[1] http://www.thefreedictionary.com/soil
[2] https://cordis.europa.eu/project/rcn/84933_en.html
[3] https://www.nal.usda.gov/topics/soil-resource-management
[4] http://soils.usda.gov/education/
[5] http://forces.si.edu/soils/
[6] https://www.bafu.admin.ch/bafu/en/home/topics/soil/publications-studies/publications/soil-a-precious-natural-resource.html
[7] http://www.earthscienceworld.org/images
[8] http://soilerosion.net/
[9] https://www.youtube.com/watch?v=YucUMhaIDww
[10] https://www.e-education.psu.edu/earth530/1647
[11] https://www.youtube.com/watch?v=mLVFevmwWWE
[12] https://www.e-education.psu.edu/earth530/1644
[13] https://www.youtube.com/watch?v=r8itOXeLm54
[14] https://www.e-education.psu.edu/earth530/1646
[15] https://www.youtube.com/watch?v=UnwS5QmR_AE
[16] https://www.e-education.psu.edu/earth530/1645
[17] http://www.globe.gov/do-globe/globe-teachers-guide/soil-pedosphere;jsessionid=4884A1A6CFBBA7F9275AA2A5EE53D9EC?p_p_id=globegovteacherguideportlet_WAR_globegovcmsportlet_INSTANCE_5esR&p_p_lifecycle=0&p_p_state=normal&p_p_mode=view&p_p_col_id=column-1&p_p_col_count=1&_globegovteacherguideportlet_WAR_globegovcmsportlet_INSTANCE_5esR_protocolCat=372023
[18] http://en.wikipedia.org/wiki/Soil_profile
[19] http://ufdc.ufl.edu/l/IR00003107/00001
[20] http://nesoil.com/properties/color/index.htm
[21] http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447039&topicorder=4&maxto=10
[22] http://en.wikipedia.org/wiki/Soil_survey
[23] http://www.nrcs.usda.gov/wps/portal/nrcs/site/national/home/
[24] http://websoilsurvey.nrcs.usda.gov/app/
[25] http://en.wikipedia.org/wiki/Soil_classification
[26] https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/edu/?cid=nrcs142p2_053588
[27] https://nhptv.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.soils/soils-around-the-world/#.WZOv64qQzBI
[28] http://www.ars.usda.gov/main/main.htm
[29] http://www.ars.usda.gov/Services/docs.htm?docid=1274
[30] http://www.enviroliteracy.org/article.php/244.html
[31] https://www.e-education.psu.edu/earth530/node/1650