Rationale for a New Approach
The subtitle, "A structural geology lab manual for the 21st Century", as well as the rationale for a new manual, needs a little explanation (and, perhaps, some justification). There are several decent structural geology lab manuals out there and the fact that a new one has not appeared in many years would suggest that the field is mature and not changing rapidly, so why write a new one? Because the field of structural geology, indeed all of geology, has changed enormously in the last decade or two. Consider the following:
Large online digital databases for topography, satellite imagery, scanned geologic maps, GPS data, earthquake data, etc. have become readily available
Digital devices are seeing increasing use in the field. We collect data using tablets and, increasingly, smart phones will replace analog compasses
Using programs, apps, and web apps to analyze data is now common place. Most structural geologists use such programs in preference to paper, whether drawing sections or plotting stereonets
The world has gone digital, but our teaching of structural geology has lagged far behind: many of the exercises that we ask students to do in structure lab have changed little over the last fifty years. We are not teaching our students how to take advantage of this new world, nor how the tools that they will use in their profession (e.g., stereonet programs) actually work internally. Digital means that, suddenly, lots of numbers are available to us. To analyze those numbers, requires some math and computing. Most of the math is just additions and multiplications done in a very systematic way, as well as, of course trigonometry. Students have much of the needed math background already (vectors, calculus) so why don't we encourage them to use those skills in their chosen major? Additional concepts, for example matrices, can be learned in the context of problems that are actually of interest to us.
Computing can take many forms but the lowest common denominator is the humble spreadsheet program, which is what Modern Structural Practice uses. Everyone already knows the basics of using a spreadsheet and it is almost certain that everyone already has a spreadsheet program on their computer.
A more mathematical approach benefits all of us in another way: it helps lay the necessary groundwork for understanding difficult concepts from mechanics. This manual has several chapters devoted to stress and strain which, of course, constitute only a very small part of the field of solid mechanics. However, the background gained will help the motivated student to understand the entirety of mechanics in subsequent studies.
The other thing that is almost entirely lacking from current lab manuals is even a passing emphasis on uncertainty and error analysis. Modern Structural Practice does not delve into these topics in great detail but does, at least, mention them. Even something as seemingly well known as the elevation of a point on the surface of the earth can vary by 15 m or more depending on the dataset used. This is particularly important when a student first encounters a geologic map or makes a measurement with a compass. If you can make a lot of measurements, which digital tools now enable us to do, then you can begin to evaluate uncertainty.
Some might question whether this approach removes us from classical geology but quite the opposite is true: if you go digital, there is a huge amount of quantitative information that can be extracted from a geologic map or a digital data set. In the past, the manual methods of extracting that information were so tedious that it was too painful to explore the map. Some of the software tools that are used in Modern Structural Practice make it trivially easy to extract quantitative 3D information which can then be analyzed as the student and professor wish.
This manual is a work in progress: The current version has been used by my own students to whom I am deeply grateful for their feedback and their willingness to try something different. I also appreciate the time that Néstor Cardozo, Haakon Fossen, David Pollard, and Ray Fletcher have taken to read over this material, though they are neither responsible for any errors nor do they necessarily endorse the overall approach! I welcome comments and suggestions from faculty and students. I know that some of the material is hard — nothing ventured nothing gained — so the type of feedback that really helps me is to help identify sections that are unclear or missing entirely. Students, please note that, while I would like to help with the solution to the exercises at the end of each chapter, I really don’t have time to do so.
My current plan is that Modern Structural Practice remain a free resource, updated periodically. It is more important to me that it is widely used (nothing like free to make that happen) than that it is published. Besides, students already pay too much for textbooks! Think of it as crowd-sourcing the revisions. The downside of this “self-published” version is that the reader has to suffer with my minimal page layout skills and limited artistic ability with the figures. An advantage is that color can be used with abandon and it is still free!
This manual is for teaching and learning. Most of the concepts herein are delivered more rigorously and in more detail in:
Allmendinger, R. W., Cardozo, N. C., and Fisher, D., 2012, Structural Geology Algorithms: Vectors & Tensors: Cambridge, England, Cambridge University Press, 289 pp.
Please refer to that published resource if you use the concepts here in your own research.