A LABORATORY EXERCISE ON SEDIMENTS AND SOILS FOR INTRODUCTORY GEOLOGY COURSES

Few laboratory manuals for introductory geology include an exercise dealing with unconsolidated sediments or soils. Many manuals cover sedimentary textures, and most introductory textbooks include soils, but few students get to examine sediments or soils in the laboratory. Since sediments and soils form a veneer over most of Earth’s surface, and much of our interaction with the Earth involves sediments and soils, including a laboratory exercise on this topic can be a valuable addition to an introductory geology course. In such a laboratory exercise students examine and handle sediment and soil samples to learn about grain size, sorting, clast composition, angularity of clasts, and organic content of soils. Although some of these characteristics can be examined in sedimentary rocks, the process of actually handling sediments and soils and feeling their differences is a more memorable experience. Based on their observations, students can make interpretations about the source region, transporting agent, and history of the various samples. Another useful exercise is to have students calculate the percent porosity by measuring how much water it takes to saturate sediment samples. That experiment can be taken one step further by having them time how long it takes water to pass through tubes filled with sediments of different grain sizes in order to test the relationships between grain size, sorting, and permeability. These exercises give them hands-on work with unconsolidated earth materials, and gets them thinking about the storage and movement of groundwater. Such a laboratory exercise on sediments and soils can enhance students' understanding of, and appreciation for, the Earth around them.