The delineation of lineations, natural linear features on imagery that represent fractures, is a particularly difficult task in areas that have long human histories. Man-made linear features may also be visible and can either lead to erroneous interpretations or assist the interpreter to correctly identify the lineations. It is thus often useful to obtain information about the history and culture of an area, particularly if human occupancy has occurred over millennia. Dartmoor in southwest England has a human history dating from at least 4000 B.C., and examples from this region are used to illustrate the impact of past human activity on the interpretation of lineations on aerial photography.
Bronze Age field boundaries (reaves) extend for great distances across the landscape, and unless one knew such features existed, they would surely be interpreted as natural linear features. Reaves are long, linear, and often parallel, and tend to cross the landscape in the same manner as lineations, regardless of the terrain. Features associated with the long mining history on Dartmoor also affect the interpretation of linear features. Surface mining of stream gravels inhibits the use of stream courses as indicators of lineations and also affects the use of valley boundaries. Linear surface excavations and rows of shafts, on the other hand, can often be used as indicators of lineations. Skill and experience are thus required to accurately interpret lineations; the greater the skill, experience, and knowledge of the human history of the area, the more complete and accurate the delineation will be.
Figures & Tables
Humans as Geologic Agents
Homo sapiens is the only known species to consciously effect change to the Earth’s geologic environment. We reshape the Earth; intensify erosion; modify rivers; change local climates; pollute water resources, soils, and geologic media; and alter soils and the biosphere. We dig holes in it, remove parts of it, and bury highly toxic materials in it. In this volume, the authors explore human impact on the Earth and attempt to answer the following questions. What have we done to Terra? How fast have we effected change? Are the changes permanent? Are they good, or have we inadvertently caused more damage? Can we, should we, repair some or all of these changes? These are important questions for the geoscience community because, as those most knowledgeable about the Earth and its resources, geologists play a major role in sustaining and preserving the Earth.