عنوان مقاله [English]
There are several fundamental issues in geomorphology, one example of which is scale. There is a special correlation between landscapes, on the one hand, and their forms’ components, on the other. This indicates a kind of scale continuity. Such rules and scale relations prevail not only at perspective level but also at the level of land forms, and thanks to the complexities of this concept in geomorphic studies, they have received less attention. However, accuracy of many geomorphic concepts is related to such concepts. Usually in scale geographic literature, a simple ratio is defined that is often used to represent the extent to which a phenomenon is reduced to its actual ratio in the maps, yet truth be told scale in geomorphology involves a broader concept: any subject that expresses a ratio lies within the conceptual realm of scale, though few geomorphologists have pointed this important issue out. Scale plays a vital role in geomorphology, both in the realm of performance and in the field of epistemology. For example, in the field of soil geology, particles’ chemical processes alter as the dimension reduces to two microns. Also, the properties of their elements generally change. Hence, in the geography of clays, which can only express the size of each substance (not their sex), chemical performance is extra important, since many vital and mineral reactions in the soil depend only on the size of the elements, not the elements themselves. Therefore, in statistical analysis, relation measurement, i.e., correlation techniques, is a concept of scale, because when you write a linear formula or other form of correlation, the ratio between the two variables is actually defined. Therefore, scale is one of the fundamental issues that, from a theoretical point of view, leads to the formation of other concepts, such as universality, fractal, river networks, geo-allometry, specific scale, etc.
Materials and Methods
In order to achieve an advanced concept of scale in geomorphology, following a relatively extensive search for books and articles in this field, several geomorphological pioneers, who used this concept in the field of scale in their works with a special theoretical innovation got selected. They included:
- John Charles Doornkamp, geographer from the University of Nottingham, England
- John Tilton Hack, American geologist and geomorphologist
- Evans, geomermologist from Durham University in UK and a graduate of York University, Canada
- Donald Lawson Turcotte, geologist from Cornell University, USA
- Benot Mendelobert, French-American mathematician from Yale University
- Dave Rosgon, hydrologist and geomorphologist from the Universities of Nevada, Montana and Colorado
- Leila Goli Mokhtari, geomorphologist from Sabzevar University, Iran
Afterwards, by selecting the books and writings of these researchers in this field, we began to study, separate, and classify their opinions, removing their repetitive content, at times shared by all of them in the process. In the final stage, we began to extract newly-found writings, specific to each of them, summarizing and analyzing their content as an opinion.
Results and Discussion
In the first step of this research, the most important result, achieved in terms of time, was the way of developments and the volume of work that has been done in this field. Review of the researchers' scientific papers showed that studies on the subject of scale of the trend have increased in the last 30 years with theoretical innovations in applying this concept becoming increasingly complex.
The second step, wherein thematic classification of the seven researchers’ opinions was of high account, dealt with semantic difference of the subject of scale. Although all these writings could be regarded as concerning the scale, the novelty of the works by these seven researchers was that they presented completely different and original interpretations and concepts, e.g. the specific scale of Evans' innovation, invariance scale of Turcotte, or geoallometry of Golemokhtari's theoretical innovations. With these initial achievements, the views of these seven researchers were then described and analyzed.
Scale in general is called the actual size of a phenomenon in geography, usually shown as a deduction or line. Fraction in numerical scales can be expressed with a fixed face and multiple denominators, e.g. in maps (1:50000 or 1:250000) and so on. Another pattern of scale display is expressed by showing a fraction with a different face and a fixed denominator, is called gradient, such as two in a thousand or five in a thousand, etc. Finally, ratio in geometry is expressed as an angle and is called a tangent.
During the last three decades, geomorphologists and related sciences have been able to apply some of the most complex concepts of scale in their works, with specific titles. These concepts include Universality Scaling, which is due to hacking, or the concept of "specific" that can be found in Evans' work. Turcotte defines the concept of invariance scale (meta-scale), whereas Mendelobert’s work on fractional scale and Rosgon’s on the thematic scale along with Goli Mokhtari, can be considered the creators and determinants of scale in geoallometry.
Finally, it can be said that each researcher has presented different concepts in the discussion of scale but the common ground among these researchers is their deeper understanding of the importance of earth and the phenomena of geomorphology. It must be confessed that the depth of their understanding of geomorphology has played a leading role in their theoretical innovation.