Interactive CRT display of bouguer gravity models in computer-assisted instruction in geology

Abstract

The objective of this study was to develop computer-assisted instruction (CAI) methods suitable for introductory and intermediate-level geology courses. This report is devoted to a description of two computer programs which provide for interactive communication between student and computer by means of a typewriter terminal and cathode ray tube (CRT). Both programs are designed for simulation experiments involving the gravitative response of bodies in the earth's crust, such as ore deposits, fault blocks, and roots of mountain ranges. Both programs provide for two-dimensional representation of buried bodies. The gravitative response of a body is obtained with the Hubbert-Talwani line integration methods of computing Bouguer gravity. In one program (CAIG), the buried body is represented by polygons, and in the other program (GRID), the buried body is created from a series of rectangular cells. Both programs provide a great deal of flexibility. The student user is guided by a series of instructions and “prompts” that are printed out on the typewriter terminal. The student is led through a series of steps in which he must make interpretations and decisions. Insofar as practical, the results of his choices are displayed as cross sections and graphs on the CRT screen. The results of the project are mixed. The experience of most users who have cooperated in testing the efficacy of the program has been favorable, in that they found the approach stimulating and thought-provoking. On the other hand, the computing-service costs of operating the programs are sufficiently high that they are probably economic only with small classes in which students are closely supervised. The use of the programs is sufficiently complicated that it is essential that an instructor be present who is familiar with their operation.