Purpose of Geological Excursions
Perhaps more than any other science, Geology is based on deductive reasoning. Many of the geologic features we observe probably evolved over thousands or millions of years, through many different processes. And from this we have to deduce what may have happened. Understanding how those features developed and evolved requires looking at the slow and rapid geological processes that are going on today. If you think that geology is just about looking at rocks and minerals, this fieldtrip may not really conform to your expectations, because although rocks and minerals provide a lot of information about Geology, they are only a part of the story. We think Geology is about understanding the Earth and how it works. At the outset, rather than be looking at rocks and minerals, we shall focus on the larger picture. Just a few basics will allow the careful observer to begin to understand how the world around us took on the shape it now has, and how ongoing geologic forces can impact our lives.
This Geological Excursion has two purposes. First, we will take a look at the topography, physiographic and geological features that characterize the Jaipur area. This will be a ‘hands-on’ look at what I think offers a better understanding of the role of geology in shaping the landscape, and the impact of geology on society. Second, and probably more important, we will have a chance to practice the technique of observational science, following the fundamental principles of the scientific method – Observe, Hypothesize, Test.
I expect that the background information on the geology of the area around Jaipur, and maps made available through this website will be useful to you in the pre-field phase, as well as when you are in the field. I also hope you enjoy the trip, and that you come away with an expanded idea of what geology is all about.
Phases of Geological Excursion:
1. Planning for Geological Excursion: Science is a step-by-step process. Once an area of interest has been identified for investigation, it is only logical to learn everything that has already been learnt about that area. Compilation of all available and relevant data is implemented in order to save on time and avoid duplication. All geological maps and reports, satellite images and aerial photographs, topographic maps, other base maps, administrative and political boundary maps, etc. must be obtained. Approval of relevant government offices or local communities must be obtained in order to avoid hostility and ensure cooperation by the local people. Issues that may hinder optimum productivity such as bad weather, wild animals and events of sudden sickness must be taken into consideration and planned for appropriately. This is also the stage when budgets must be prepared both in terms of costs and the number of people to be involved. It is advisable to involve the local community when employing casual laborers or language translators, since they understand the area better than those brought in from outside, and will thus be quick to pinpoint areas that maybe of interest. Furthermore, they are the best suited to relate historical events where necessary. In a tropical country like India, it is advisable to plan for field studies during the dry seasons. It is good practice to begin field work early in the morning so as to accomplish substantial work before it becomes too hot during the noon.
2. Field Observation/Data Collection: There are several reasons for undertaking a geological excursion, but all of them involve collecting variable amounts of field data. The importance of careful, accurate and systematic observations cannot be overemphasized. For making observations, a geologist has to visit predefined locations in field, which may have been identified through a study of high resolution satellite imagery during the planning stage. Data with regard to rock types, their mineralogy, attitude of bedding, folds, faults, unconformities etc., are recorded in the field. Notes describing the details of geology and structure are recorded right at the outcrop. The geologist must be fully equipped with all the necessary tools and materials, and be mentally prepared to take note of not only geological features, but of others that may be influenced by the geological characteristics of the area. For example, vegetation density may be used to identify the variation in lithology; vegetation growing in a certain alignment may indicate faults; abrupt deviations in the courses of streams may indicate presence of faults; offset of stream segments may be interpreted in terms of the magnitude of displacement along such faults. No amount of information is too much, therefore all possible data – no matter how insignificant it may seem at the time – should be collected. A field geologist must take geotagged photographs of features of interest as often as required, for these can later be attached to their correct spatial locations in maps through any GIS application.
Precise location of the observation point is determined with the aid of a GPS receiver, preferably used in assisted GPS (aGPS) mode. The position is determined as accurately as possible and noted in the field diary as well as saved as a *.gpx, *.kml or *.kmz file so that it may later be read by a GIS application. Whilst taking readings, accuracy should be emphasized. Discussions on contentious geological and other issues amongst members of the field party go a long way in making a mapping programme successful. For more details, see the article Field Procedures.
3. Report Writing: A geological report is a concise, informative and well documented narrative used to present, analyze and summarize field data for all types of users. A geological report should always accompany a geological map, and must be supported by figures, stratigraphic columns, tables, graphs, etc. A geological report should contain the following headings:
c) Stratigraphy and Lithology
e) Geological History
Numbering the sections is optional as long as they are clearly identified and placed in the table of contents. It is also acceptable to break each section down with subheadings (ensure they are clearly labeled), for example having a different subheading for each lithology (under Stratigraphy). The graphics must be accompanied by brief, informative captions. Each figure and table should be sequentially ordered (Fig 1, Fig 2, Fig 3, etc.). It must be ensured that all photographs and diagrams have a scale and direction of view, either in the photo/diagram itself, or in the caption. Figures must always be quoted in the appropriate places in the text (place the figure number in brackets after you have discussed what the figure is showing). A list of studied outcrops with their grid references, as also observations and any data obtained at each outcrop, should be attached to the end of the report as an Appendix. Should you quote from some other source in your report, always remember to quote the original source, and mention its details in the reference section at the end of the report.
Upon completion of this Geological Excursion students should be able to:
1. Identify rock types and interpret their mode of formation;
2. Use observations to make interpretations about the geologic history of the area;
3. Describe the dynamics of regional geologic processes;
4. Explain the interaction of bedrock and surface processes in the landscape in and around Jaipur;
5. Understand how the geology and landscape impact human settlement.
Information - Aravalli Craton
and the Delhi Fold Belt
This website is hosted by
Department of Geology
Aligarh Muslim University, Aligarh - 202 002 (India)