ASBOG FG PG common mistakes
ASBOG FG PG · Understand the traps and how to avoid them.
Computes hydraulic conductivity or transmissivity but leaves units inconsistent - e.g., plugs feet/day values into a formula expecting m/d, or mixes gpd/ft² with ft/day without converting, and reports a number without checking magnitude.
Candidates memorize T = Kb and Darcy's law as symbol strings, then substitute numbers from the prompt without tracking dimensions; the exam deliberately mixes unit systems (gpd, cfs, ft, m, gal) to test this.
What to do instead
Write the unit next to every number before calculating, convert everything to one consistent system (typically ft/day or m/day) in a first step, and sanity-check the answer's order of magnitude (K for sand is ~10⁻³ to 10 ft/day, not 10⁶).
Determines groundwater flow direction parallel to water-table contours, or averages the head at three wells instead of solving the three-point problem geometrically.
Flow-direction questions look like simple arithmetic; candidates skip the step of constructing contours or perpendiculars and answer with the steepest single gradient between two arbitrary wells.
What to do instead
Always sketch the three well locations to scale, interpolate the head value equal to the intermediate well along the line joining the high and low wells, draw the contour through that point and the intermediate well, then draw flow perpendicular to the contour, downgradient.
Records strike and dip using the wrong-handed convention, or computes apparent dip from a cross-section without resolving the angle between the section line and true dip direction.
Left-hand vs right-hand rule and the cosine relationship for apparent dip are easy to state but are applied under time pressure without a sketch, so the section azimuth is ignored.
What to do instead
Draw a compass rose with the bedding plane and section line on every structure problem; use tan(apparent dip) = tan(true dip) × sin(angle between section line and strike), and state the right-hand rule explicitly before writing the answer.
Assigns a fault type to a stress regime or plate boundary by name-matching (e.g., calling a transform boundary 'thrust' because it is convergent) rather than reasoning from the principal stress directions.
Candidates memorize boundary-fault pairs as lists, and the exam phrases questions in terms of σ1 orientation or local structures, which breaks the memorized pairing.
What to do instead
Derive fault type from σ1: vertical σ1 = normal, horizontal σ1 with vertical σ3 = thrust/reverse, both horizontal = strike-slip. Then map boundary type to stress field, not directly to fault name.
Classifies an igneous rock from its colour index or a single mineral (e.g., 'dark and shiny = basalt') instead of plotting modal mineralogy on QAPF or applying Bowen's reaction series to interpret texture and sequence.
Hand-specimen habits from lab are faster than modal counting, and Bowen's series is memorized as an order rather than used to explain zoning, resorption, or disequilibrium textures.
What to do instead
For classification questions, identify quartz, alkali feldspar, and plagioclase proportions first and place the rock on the QAPF diagram; use Bowen's series to explain observed textures (zoned plagioclase, reaction rims) rather than to name the rock.
Identifies minerals by colour or 'look' rather than by diagnostic properties, and fails to distinguish look-alikes such as quartz vs calcite vs halite, or hornblende vs augite.
Colour is the most salient property and the easiest to recall, but it is the least diagnostic; candidates underuse cleavage, hardness, streak, and reaction with acid under exam conditions.
What to do instead
Run a fixed checklist for every mineral question - hardness, cleavage/fracture, lustre, streak, acid reaction, and crystal form - and eliminate look-alikes on at least two properties before choosing.
Applies the Dunham classification to a carbonate described only by grain size, or reads a vertical stratigraphic column as a single continuous deepening without checking for parasequence stacking and flooding surfaces.
Dunham's terms (mudstone, wackestone, packstone, grainstone) sound like textural/grain-size terms, and stratigraphic columns are read top-to-bottom as a story rather than analysed for stacking patterns.
What to do instead
Use Dunham only when the描述 specifies mud support vs grain support; for stratigraphy, mark flooding surfaces and note whether facies stack coarsening-upward (progradation) or fining-upward (transgression) before interpreting sea-level change.
Calculates slope factor of safety using total normal stress and ignores pore-water pressure, or treats liquefaction potential as a function of grain size alone without considering saturation, density, and drainage.
Textbook FoS = resisting/ driving forces is applied with the simplest block model; the effective-stress principle is understood conceptually but not carried into the arithmetic under time pressure.
What to do instead
Always write the effective-stress form (τ = c' + (σ − u)tanφ') first, compute u from the water table or seepage condition, and for liquefaction check all three preconditions - loose, saturated, and rapid loading (or no drainage).
Identifies a drainage pattern or landform from a single descriptive keyword (e.g., 'dendritic' for any branching stream) without matching it to the underlying bedrock/structural control described in the stem.
Landform names are learned as vocabulary lists with picture associations, but the exam supplies only text descriptions of lithology, structure, and topography.
What to do instead
Extract the controlling variable from the stem - uniform resistant rock (dendritic), alternating resistant/weak beds (trellis), domed upland (radial), fractured granite (rectangular) - and choose the pattern from the control, not the keyword.
Matches an ore deposit to a tectonic setting or host rock from a memorized list (e.g., all porphyry deposits to 'convergent margins' without distinguishing the intrusive host, alteration zoning, or metal association), or confuses VMS with SEDEX.
Deposit-type lists are memorized as one-to-one pairs, but exam items describe alteration assemblages, host lithology, and metal ratios and expect the candidate to reason to the deposit class.
What to do instead
Build a table with four columns per deposit type - tectonic setting, host rock, alteration/mineralogy, and metal association - and answer from the diagnostic features given in the stem (e.g., seafloor exhalative vs basinal brine).