By the end of this course on Geological Structures you should be able to:
- Describe common geological structures in maps, outcrops and samples, using terms that can be understood by other geologists;
- Construct geological cross-sections based on evidence in maps;
- Calculate angles and distances between geological structures using data from geological maps;
- Interpret the history of changes in the Earth’s crust that produced geological structures observed at the Earth’s surface.
This manual is about structures that occur within the Earth’s crust. Structures are the features that allow geologists to figure out how parts of the Earth have changed position, orientation, size and shape over time. This work requires careful observation and measurements of features at the surface of the Earth, and deductions about what’s below the surface. The practical skills you will learn in this course form the foundation for much of what is known about the history of the Earth, and are important tools for exploring the subsurface. They are essential for Earth scientists of all kinds.
The course that this document supports is about doing structural geology. It’s not possible to be a good geologist (or to pass the course) just by learning facts. You have to be able to solve problems. Do your lab work conscientiously and get as much as possible done during lab sessions when instructors are available to help you.
This manual consists of both readings and lab exercises, which alternate through the text. The readings are designed to be read and understood outside the lab sessions, whereas the labs contain specific instructions and questions to be completed. Before each lab, be sure you have covered the readings that come immediately before it.
Many problems in structural geology involve thinking in three dimensions. This is the largest challenge that you will face in working with the material in this book. Different people use different strategies for thinking in 3D. Your instructors will sometimes be able to offer a range of strategies and techniques. Make use of their skills whenever you have difficulty.
This manual was written to support the course “EAS233 Geologic Structures” at the University of Alberta in Canada. The course is typically taught between January and April. During January and February it is too cold for effective geological fieldwork, so the outdoor lab (lab 9) takes place toward the end of the class. In a warmer climate, the data collection part of this lab could be done earlier in the course.
A word on language: Canadian English, and Canadian geology, follow a mixture of British and American traditions. For example, British geologists will always speak of “geological structures” whereas Americans may say “geologic structures”. The British Carboniferous Period is equivalent to the Mississippian and Pennsylvanian in the U.S. Canadian geology follows a mixture of both traditions which can sometimes seem aggravatingly inconsistent. However, we encourage readers to embrace this diversity in the interests of encouraging communication between those interested in the Earth on both sides of the Atlantic!
Things you should know before you start
You should have completed a course in introductory geology. Here are some of the things you are expected to know.
- Maps and map scales: You should be able to convert a map scale expressed as a representative fraction (e.g. 1:50,000) to a map scale expressed in metric or imperial length units (2 cm = 1 km) and draw a scale bar based on either. You should understand topographic contours and should be able to look at a map with topographic contours and identify hills, valleys, and predict which way streams are flowing.
- Plate tectonics: Know the difference between continental and oceanic lithosphere, and the three major types of plate boundary: spreading centres, subduction zones, transform faults.
- Minerals: Common rock-forming minerals such as quartz, feldspar, mica, amphibole, calcite.
- Basic rock types: You should know the names of basic rock types and be able to identify them. At minimum, these should include the following:
- Igneous rocks: granite, diorite gabbro, peridotite, rhyolite, andesite, basalt, tuff.
- Sedimentary rocks: conglomerate, sandstone, mudstone and shale, limestone, dolostone, coal, chert, rock salt, gypsum.
- Metamorphic rocks: slate, schist, gneiss, granofels, quartzite, marble.
- Geological time: You should know the sequence of eons: Archean, Proterozoic, Phanerozoic, and within the Phanerozoic you should know the names of the eras and periods by heart.
- Paleozoic: Cambrian, Ordovician, Silurian, Devonian, Carboniferous (Mississippian, Pennsylvanian), Permian.
- Mesozoic: Triassic, Jurassic, Cretaceous.
- Cenozoic: Paleogene, Neogene, Quaternary.
We will assume you are familiar with these terms and their meanings. If any of them are unfamiliar, now is the time to review the material from your introductory classes and make sure you know them!
Before you work on the first assignment
Before you come to lab, read the relevant sections of this book, and any other assigned reading, carefully.
- Set up your work on each assignment with a cover page so that it’s easy to review and mark. The first page of each set of answers for the assignments should consist of a sheet of paper with (1) your name, (2) EAS 233, (3) Assignment X, (4) your laboratory section, and (5) the date of submission.
- Pass in only those pages of this book on which you have done work. Keep the instructional pages when possible, so that you can refer to them while your assignment is being marked.
- Along with the answer to each problem for an assignment, you should show the work that enabled you to arrive at the answer. There are several reasons for this. First, it’s sound scientific practice. Second, you are less likely to make mistakes. Third, if your work shows that you used a correct method but made a minor error, you may still get most of the marks; a wrong answer on its own is not worth any marks at all!.
- Make use of your lab sections and TAs. Try to solve and complete an assignment during your lab section and hand your assignment in at the end of your lab section. If you need more time to complete an assignment, there will be deadlines for handing them in; these will be announced by the TAs in the first lab.
- If you make a mistake that can’t be corrected with a simple erasure, it’s ok to place a piece of tracing paper over the original version and complete your answer on the tracing paper. Note that you don’t need to trace the entire question. Just mark the corners or some other conspicuous points so that someone marking your work can place your tracing paper over a clean original to see what you have done.
- Some questions are designated for self-marking. These will be marked with an *asterisk. These will be assessed only as ‘complete’ or ‘incomplete’ during marking, but they must be completed to obtain full marks for the lab. Answers will be provided for checking during the following lab. You are advised to complete them conscientiously, as the skills involved will be tested in the exams. If you find you have done poorly in a self-marked question, make sure you know where you went wrong, or ask for help from a teaching assistant. Note that the rules for academic integrity and plagiarism apply to the self-marking questions: an answer copied from someone else is a breach of the academic code of conduct and is subject to the same penalties as any other kind of copying.
- Completed labs should be placed in the appropriate slot for your lab section.
- Grading key if deadline is missed: Max. 70% after deadline; 0 (zero) after assignments were returned (typically your next lab session).
All work you present for evaluation in any course must be your own work. It is an academic offense if you:
- present someone else’s work as your own (plagiarism);
- gain an unfair advantage in a test or an exam (cheating);
- distort the truth for advantage (misrepresentation of facts);
- encourage or help anyone else to do any of these things.
In this course you will sometimes benefit from discussions with other students as well as teaching assistants, especially in the labs. Although this discussion may help you decide how to solve problems in structural geology, the actual answers you write down must be written in words and sentences composed by you alone, diagrams must be drawn by you, and any measurements or calculations must be carried out separately by you. It is not acceptable to share a calculator in determining the answers to questions. Note that these rules apply to ‘self marking’ questions just as much as to questions that will be given a numerical mark.