Measurement of compass orientations of rock fractures
Thomas W. Oesleby Northwest College
This is a partially developed activity description. It is included in the collection
because it contains ideas useful for teaching even though it is incomplete.
Students learn to use a geologic compass to measure rock fractures and formulate a hypothesis to explain the origin of the fractures
GSA Poster (PowerPoint 3.4MB Jan12 04)
Higher Order Thinking Skills:
Interpretation of data; formulation of a hypothesis
use of a geologic compass
6-8 through undergraduate entry, general public
Use of a protractor
Role of Activity in a Course:
part of a sequence of laboratory exercises on rocks and field trips
Data, Tools and Logistics
simple geological compasses
some students require minor additional instruction using a compass.
Students plot fracture rose diagrams and write a report summarizing procedure, results and a hypothesis
Students are taken on a field trip to a glacial moraine. Students are grouped into pairs, and each pair is given an instruction sheet (which includes a table for recording data) and a geologic compass. Following a brief demonstration on the use of a geologic compass to measure azimuths of vertical and near-vertical fractures on boulders, the student pairs are sent off in different directions with instructions to each measure fracture orientations on 20 boulders (ten per student) and to take about 20 minutes to complete the task. Instructions also request a basic lithologic identification of each boulder studied. As part of their follow-up report, students plot fracture orientations into a rose diagram, and then speculate on the origin or cause of the fractures by formulating a hypothesis.