Question 14 of 21: Question 5, Part 1: Multiple Choice

Question 5, Part 1: Multiple Choice (15 marks)

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.

1) → (c). Glaciers' direct geologic role is mechanical: eroding the landscape (abrasion, plucking) and transporting/depositing the resulting sediment (till, outwash) – they do not directly raise sea level by "depressing the crust" (isostatic depression is a secondary, delayed response) nor warm climate.

2) → (d) very much slower; vastly more. Glacial ice flows at metres-per-day to metres-per-year rates – orders of magnitude slower than stream flow – yet a glacier's basal and englacial transport carries a vastly larger total sediment load (till plus entrained debris of all sizes) than the equivalent stream.

3) → (d) the basal, sliding zone. Abrasion (rock-on-rock scouring) and plucking (quarrying blocks loosened by meltwater freeze-thaw) both require the ice to be in direct, sliding contact with the bed – the basal zone, not the internal flowage or surface brittle zone.

4) → (b) U-shaped valley. Alpine (valley) glaciers erode their host valley into a broad, U-shaped cross-profile (widening and deepening a former V-shaped stream valley); V-shaped valleys are the fluvial (non-glacial) form.

5) → (c). A fjord is a glacially deepened, U-shaped valley along a coast that is subsequently flooded by rising (post-glacial, eustatic) sea level – not itself created by crustal rebound (option a) or a moraine dam (option d).

6) → (b). "Glacial drift" is the general umbrella term for ALL sediment of glacial origin, both unsorted till and sorted/stratified meltwater outwash – not a flow process or an ice-sheet advance itself.

7) → (d) is FALSE. Glacial erratics are, by definition, blocks that glaciers DID successfully transport (often great distances from their source) – they are not "too large to move"; (a), (b), and (c) are all standard true facts about till vs. outwash.

8) → (d). Drumlins are smooth, elongate, asymmetric till mounds (blunt stoss end, tapered lee end) streamlined and shaped beneath moving CONTINENTAL ice, not outwash mounds or bedrock-erosional forms.

9) → (d) is the exception. "Rock flour deposited directly from advancing ice" describes till (unsorted, ice-deposited), the opposite of stratified drift, which by definition is sorted/layered sediment reworked and deposited BY MELTWATER (a, b, c all correctly describe stratified drift).

10) → (b) esker. An esker is the sinuous, sand-and-gravel-filled cast of a former subglacial or englacial meltwater tunnel, left standing as a ridge after the ice melts away.

11) → (b). Pleistocene proglacial lakes (Lake Agassiz and enlarged predecessors of today's Great Lakes) were vastly larger than their modern remnants, dammed by ice and fed by meltwater; horns/arêtes/cirques and terminal moraines existed but are not "larger" in the same directly comparable sense today.

12) → (b) Basal slip. The three recognized glacier-motion mechanisms are internal (plastic) flow, basal slip (sliding on a meltwater film), and bed deformation (subglacial till deformation); frost heaving, morainal sliding, and "crevassal slip" are not among them.

13) → (b) drumlin. Drumlins are streamlined till hills moulded beneath advancing CONTINENTAL ice sheets (see item 8), and drumlin fields are a hallmark of formerly glaciated continental lowlands; they are not characteristic of alpine glaciers. Moraines (a) are also till, but they form under BOTH glacier types: lateral and medial moraines are classic alpine features. So a moraine does not satisfy the "not with alpine glaciers" condition. Cirques (c) are erosional alpine features, and outwash (d) is meltwater-sorted, not till.

14) → (a) Wisconsinan. The Wisconsinan glaciation (ending ≈11,700 years ago) was the most recent major North American Pleistocene ice advance; Kansan, "Indianan," and "Dakotan" are either older or not standard stage names.

15) → (b) Pleistocene Epoch. The most recent "Ice Age" (major continental glaciation) corresponds to the Pleistocene Epoch (≈2.58 Ma–11.7 ka); the Proterozoic, Permian, and Pliocene are all much older intervals (though earlier glaciations did occur in some of them, none is "Earth's most recent Ice Age").