The Importance of Field Geology
Why Field Geology?Geology is related to all the physical sciences. As observed by Charles Lyell in 1833 "a geologist should be well versed in chemistry, natural philosophy, mineralogy, zoology, comparative anatomy, botany; in short, in every science relating to organic and inorganic nature." In each of these physical sciences, knowledge and understanding is obtained (and retained) most successfully by direct observation of natural phenomena. Similarly, the science of geology has its basis in the study of rock exposures and geologic processes. Earliest systematic observations date to the mid 17th century when Nicholas Steno laid the foundations of modern stratigraphy by careful field work in Italy. Our present understanding of the science is rooted in careful field observations by William Smith, James Hutton, Charles Lyell, Adam Sedgwick, and Roderick Murchison to name a few. Nearly all geologic literature through the early 20th Century was based exclusively on field observation. Even with the advent of remote sensing techniques such as seismic studies, gravity and magnetic studies, and ultimately space-based satellite imagery, field-based geology remains the keystone of the science. To underscore the point, a survey of current geology journals will reveal that most studies have their basis in field observation and sampling. Therefore, it is essential that the student of geology have a strong background in field observation. Even those students who do not consider geology as their ultimate degree goal need to understand the value and role of field observation in the science. Field observation in geology focuses on two broad areas: ongoing geologic process and outcrops of rocks. Most geologic processes are too localized (e.g. beach processes), transient (e.g. earthquakes, volcanoes, floods, and landslides) or slow (e.g. erosion of mountains) to be readily available for student examination. However, rock outcrops are enduring and contain an incredible amount of information on earth history. I tell my students "every rock has a story." If you examine a rock closely, you will be able to "read" the history in that rock; and if you have a section of rock layers, you may read them like pages in a history book. This "reading" is done by examining such clues such as rock composition, grain size, grain shape, rock color, and sedimentary structures such as cross-bedding, ripple marks, mud cracks, etc. From these clues, even a beginning geology student with the proper instruction will be able to interpret the depositional environment of the rocks. In other words, we can determine how these rock were originally deposited and in what environment (e.g. beach, swamp, river, lagoon, etc.). By examining the fossils in the rocks, the trained student can make inferences as to the ancient climate, ecosystems, sea water temperature, depth, and salinity. All of these concepts may be taught in the classroom and practiced in lab exercises. However, the opportunity to get out in the field allows the student to see these geologic features in their natural state, in their natural context, and at the proper scale.
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