Field and Practical Skills
Field and Practical Skills tests geological mapping, compass-clinometer use, strike and dip measurement, sampling, hand-specimen identification and map reading.
Core skills
- Brunton compass: measure strike, dip and dip direction; correct for magnetic declination.
- True dip is the maximum dip; apparent dip is less and depends on section orientation.
- Field notes record location, lithology, structure, sample number and date.
- Geological map: scale, legend, cross-section and topographic base.
- Hand specimen: use lustre, hardness, cleavage, colour, streak and grain size.
Worked example
A bed has true dip 40 degrees and an apparent dip of 30 degrees in a section. Reasoning: apparent dip is always less than true dip and equals true dip only when the section is perpendicular to strike. Since 30 is less than 40, the section is oblique to strike.
Traps
Do not record dip without direction. Magnetic declination must be added or subtracted correctly. A hand specimen with one cleavage surface is not enough to identify a mineral. Always check map scale before measuring distances.