04-BS-14 · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams May 2018 — 04-BS-14, Geology. Closed-book, 3 hours; candidates may use only a Casio or Sharp-approved calculator. Four questions constitute a complete exam paper (Questions 1–3 mandatory). On Question 4, per the exam notes only the first four (4) answers as they appear in the answer book are normally marked; all nine (35–43) are answered here as a complete study resource. Total marks for the exam = 100.
Reference texts: Marshak, Earth: Portrait of a Planet (mineralogy, rock textures, Bowen's Reaction Series, structural geology, drainage patterns, glacial/periglacial landforms, plate tectonics, relative dating and unconformities); Goodman, engineering-geology mapping and mass-wasting methods; Freeze & Cherry, Groundwater (Darcy's law, hydraulic head, advective transport).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
| # | Statement | Answer | Why |
|---|---|---|---|
| 21 | Quartz weathers readily to aluminum-rich clay minerals | FALSE | Quartz is chemically inert (strong Si–O bonds, no cleavage, no aluminum in its formula) and highly resistant to weathering — it survives as sand grains rather than breaking down to clay. Feldspars, not quartz, hydrolyse to clay minerals. |
| 22 | Feldspars commonly decompose during weathering to clay minerals, silica, and soluble constituents | TRUE | Hydrolysis of feldspar (e.g. K-feldspar + carbonic acid → kaolinite + dissolved silica + K⁺/HCO₃⁻ in solution) is the textbook reaction that produces clay minerals. |
| 23 | High-temperature ferromagnesian minerals (olivine, pyroxene) are generally much LESS susceptible to weathering than quartz | FALSE | The Goldich weathering-stability series mirrors Bowen's Reaction Series in reverse: minerals that crystallize first at high temperature (olivine, Ca-plagioclase) are LEAST stable at surface conditions and weather fastest; quartz, crystallizing last, is the most weathering-resistant common silicate — the opposite of the statement. |
| 24 | There is no geologic evidence that mid-ocean ridges spread at uniform rates or symmetrically | TRUE | Spreading rates vary considerably between ridge systems (slow Mid-Atlantic ~2–5 cm/yr vs. fast East Pacific Rise ~6–16 cm/yr) and magnetic-stripe widths record asymmetry across a given ridge segment as well. |
| 25 | As dense seafloor subducts it penetrates and ruptures the mantle, causing the LARGEST earthquakes as the mantle fractures | FALSE | The largest earthquakes (megathrust events, M>8.5) occur on the shallow, brittle interface between the overriding and subducting plates, not from the slab "rupturing" the surrounding mantle at depth; deep-focus slab earthquakes are a distinct, smaller-magnitude phenomenon with a different (phase-transformation) mechanism. |
| 26 | Calcite and halite both react with dilute acids to evolve carbon dioxide | FALSE | Calcite (CaCO₃) fizzes with dilute HCl, releasing CO₂ — the standard field carbonate test. Halite (NaCl) has no carbonate group and simply dissolves; it does not effervesce. |
| 27 | Colour is one of the most diagnostic properties of minerals | FALSE | Colour is notoriously unreliable because trace impurities can radically change it (e.g. quartz appears clear, purple, pink or smoky); streak, hardness, cleavage and crystal habit are far more diagnostic identification properties. |
| 28 | The Richter magnitude scale is based on total energy released, as measured on a seismograph | FALSE | The Richter (local magnitude) scale is based on the logarithm of the maximum seismic-wave amplitude recorded at a standard distance, empirically corrected — not a direct energy measurement. Moment magnitude (Mw) is the scale tied to total radiated seismic-moment energy. |
| 29 | Rocks of the continental crust are generally less dense than rocks of the oceanic crust | TRUE | Continental crust is felsic (~2.7 g/cm³, granitic); oceanic crust is mafic (~3.0 g/cm³, basaltic/gabbroic). This density contrast is why continents "float" higher and oceanic crust preferentially subducts. |
| 30 | Evidence for Pangaea includes fit of continents, matching fossils/mountain chains separated by oceans, and ancient glaciated rocks in the southern hemisphere | TRUE | These are Wegener's classic lines of evidence for continental drift/Pangaea, later given a mechanistic explanation by plate tectonics. |
