04-BS-14 · December 2015
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams December 2015 — 04-BS-14, Geology. Closed-book, 3 hours. Five questions constitute a complete paper: Questions 1-4 are mandatory and one of Questions 5-7 must be chosen; every question (5, 6, and 7) is answered here as a complete study resource. Marks for each sub-part are printed as given in the source; totals are transcribed as printed, not forced to a uniform 20.
Reference texts: Marshak, Earth: Portrait of a Planet (structural geology, relative dating, weathering, glacial and fluvial landforms, mineralogy/igneous classification); Goodman, engineering-geology mapping methods (strike and dip, cross-cutting relationships); Freeze & Cherry, Groundwater (water table, zones of aeration/saturation, well hydraulics).
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.
| # | Item | Answer | Why |
|---|---|---|---|
| 1 | Three types of differential stress in the Earth's lithosphere? | c) compression, shear, and tension | These are the three fundamental stress states that deform rock: compression (shortening), tension (stretching/extension) and shear (offset along a plane). (a), (b) and (d) are not recognized stress classes. |
| 2 | During mountain building, flat-lying sedimentary/volcanic rocks are often bent into a series of ____. | a) folded anticlines and synclines | Compressional orogenic stress folds layered rock into alternating up-arched (anticline) and down-sagged (syncline) structures; horsts/grabens (c) are extensional fault-bounded blocks, not folds. |
| 3 | Physical removal of dissolved/disaggregated rock from the weathering site by wind, water or ice. | d) erosion | Erosion is specifically the transport/removal step, distinct from weathering (the in-place breakdown that precedes it) and from ablation (glacial ice/snow loss) or solifluction (a specific slow soil-flow process). |
| 4 | ____ is one of the three ways a glacier can move over its bed. | b) Basal slip | Glaciers move by (i) internal plastic deformation/creep of ice crystals, (ii) basal slip/sliding on a thin film of meltwater at the ice-bed interface, and (iii) deformation of a soft, water-saturated sediment bed beneath the ice. Frost heaving, morainal and crevassal “sliding” are not recognized glacier-motion mechanisms. |
| 5 | A(n) ____ is a depositional feature composed primarily of till, associated with continental (not alpine) glaciation. | b) drumlin | Drumlins are streamlined till hills formed in swarms beneath continental ice sheets. Moraines (a) also occur with alpine glaciers; cirques (c) are alpine-erosional, not depositional; outwash deposits (d) are stratified meltwater sediment, not till. |
| 6 | A syncline is ____. | b) a fold in which older flanking strata dip toward the axis | A syncline is a trough-shaped fold with the youngest strata preserved in its core; both limbs dip inward, toward the axis, so the relatively older strata on the outer flanks dip toward (down into) the axis. (d) instead describes an anticline (older strata in the core, dipping away from the axis); (a) describes a monocline. |
| 7 | Which of the following best defines a mineral and a rock? | c) In a mineral the constituent atoms are bonded in a regular, repetitive, internal structure; a rock is a lithified or consolidated aggregate of minerals. | Same defining pair as Q1 item 10: ordered crystal structure defines a mineral; a consolidated aggregate of minerals defines a rock. |
| 8 | Which statement concerning glacial deposits is FALSE? | d) Glacial erratics are blocks of rock that are too large for the glacier to move. | By definition an erratic was transported by the glacier, sometimes over great distances and regardless of size (glaciers routinely move house-sized boulders) — the statement's claim is the opposite of what “erratic” means. (a), (b) and (c) are all accurate: till is ice-deposited and unsorted/angular, outwash is meltwater-stratified sand and gravel. |
| 9 | Drumlin fields contain ____. | d) smooth, tapering, asymmetric ridges of till usually formed and shaped beneath a continental ice sheet. | This is the standard definition of a drumlin (blunt/steep stoss end, tapered lee end, subglacially moulded till). (a) describes kames/outwash mounds, (b) describes roches moutonnées (bedrock, not till), (c) describes cirques/kettle depressions. |
| 10 | ____ is the dissolution or decomposition of minerals and rocks. | b) Chemical weathering | Chemical weathering is the broad category covering dissolution, hydrolysis, oxidation and carbonation reactions that decompose minerals in place. Hydrolysis (c) is one specific chemical-weathering reaction, not the general term the question asks for; mechanical weathering (a) disaggregates rock physically without altering mineral chemistry. |
A drainage basin's stream network takes on a characteristic geometric pattern that reflects the underlying rock structure, resistance and slope. Three common types, distinct from the “confused/deranged” and “circumferential/radial” patterns already covered in Q1 item 3:
