Design and assessment of an interactive digital tutorial for undergraduate-level sandstone petrology

Journal of Geoscience Education, Sep 2003 by Milliken, K L, Barufaldi, J P, McBride, E F, Choh, S-J

ABSTRACT

A digital interactive tutorial has been created to provide undergraduates a 'virtual microscope' resource for learning sandstone petrology. The tutorial does not replace hands-on laboratory experiences with the petrographic microscope, but lends efficiency and breadth to the learning process. Students are able to obtain practice with identification of a wide array of sandstone components outside of the laboratory and independently of the instructor.

The efficacy of traditional petrography instruction versus instruction supplemented by the tutorial was assessed in two semesters of GEO 416M, "Sedimentary Rocks" at the University of Texas at Austin. Students in the first semester were not provided with the tutorial, providing a baseline or control for comparison. In the second semester, the digital tutorial was provided to all students on CD and assigned as a required resource in laboratory exercises. Investigation of student attitudes towards the tutorial demonstrates a high level of approval, and subject matter attainment appears to improve with tutorial use. Individualized, one-on-one instruction should remain a key element in effective teaching of petrography. Digital materials have a clear benefit in terms of enhancing the quality, availability, and breadth of the demonstration materials that can be provided to students. Based on this preliminary assessment, there are benefits in student learning as well.

Key words: petrography, sandstones, sedimentary petrology, educational assessment, digital imaging

INTRODUCTION

Hands-on experiences with earth materials are a vital aspect of earth science education. The need for petroleum explorationists or mining geologists to have extensive first-hand knowledge about the natural variations of rock properties is obvious. In fact, it is difficult to imagine an area of earth sciences for which knowledge and understanding of rock properties is irrelevant. Interestingly, as undergraduate earth science departments adopt an increasingly broad view of their curricular needs, the most intensively hands-on study of earth materials, perography, is being squeezed from the curriculum. Despite this trend, students of even the most broadly defined earth science areas, for example, hydrologists, environmental scientists, and geo-physicists, have considerable stake in obtaining a detailed understanding of earth materials.

We have developed and tested an interactive digital tutorial in sandstone petrology. The goal of this tutorial is to provide students exposure to the highly visual subject matter of petrography outside the confines of organized laboratory exercises. Our hope is that widespread use of such digital interactive formats will allow students to gain high levels of expertise with description and interpretation of earth materials despite the reduced amounts of hands-on laboratory practice that are allowed by modern curricula.

PETROGRAPHY INSTRUCTION IN THE MODERN EARTH SCIENCES CURRICULUM

It is inescapable that instruction in petrography is labor-intensive, and therefore expensive. Further expense relates to the cost of microscopy equipment and thin sections. Expertise with microscopy is attained through repeated exposure to large amounts of visual information. Teaching of petrography necessarily depends upon the involvement of an instructor who has already attained this expertise. In a typical laboratory session, an instructor with extensive experience in the identification and interpretation of microscopic features, conveys this information by demonstrations to a small group of students. After having received the instruction on how to locate and identify a given feature, the student is then called upon to make independently such identification and to have the correctness of their interpretation confirmed by the instructor. Typically, this proceeds through a repeated exchange in which students locate a feature, question the instructor about it, and in turn are interrogated about other features located by the instructor. Extensive practice outside of the laboratory is a key element to gaining petrographic expertise, but especially at the beginning of this process, individualized attention from the instructor is indispensable. Accomplishing petrographic instruction depends not only upon the availability of an experienced petrographer and but also on the availability of suitable demonstration materials (thin sections) and working petrographic microsocopes.

Cost aside, the principal reason that petrographic instruction is disappearing from the modern curriculum relates to the fact that it must compete for time within an increasingly diverse list of required courses (e.g., Fitz, 2000). Experiences in the Department of Geological Sciences at the University of Texas at Austin are illustrative of the challenges for retaining petrography in the curriculum. Until the mid-1980s undergraduates in this department took two required courses in sedimentary materials. The first course, offered to sophomores, was GEO 416M, "Sedimentary Rocks". This course covered hand specimen petrology, measured sections and core description, and depositional environments for both siliciclastic and carbonate sediments and rocks. Two laboratory sessions a week gave the students hands-on experiences. A second course, GEO 336K, "Sedimentary and Metamorphic Rocks" was offered to juniors and seniors. Prerequisites were a semester in mineralogy and a semester in igneous petrology both including a substantial component of optical crystallography. The GEO 336K course devoted a half-semester to the petrography of siliciclastic and carbonate sediments and rocks. Again, students attended two laboratory sessions each week, for totals of six sessions devoted to siliciclastics and six to carbonates. These materials were examined with respect to provenance, geochemical history, and porosity evolution. In the wake of added departmental requirements for undergraduates, including courses in geophysics and hydrogeology, the sedimentary rocks curriculum contracted. Today, petrology instruction is subsumed under GEO 416M and students only receive 3 laboratory exercises in petrography of sandstones and 3 in carbonates (shales and evaporites are completely omitted). One disadvantage to this arrangement is that students are introduced to microscopic observations without grounding in mineralogy, crystallography, or crystal optics.