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.
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