Short Answer (Paragraph) and Fill in the Blank: 04-BS-14, December 2015, Q5

Question 5: Short Answer (Paragraph) and Fill in the Blank (20 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.

1a) Glacial erosional landforms (three)

Cirque — a bowl-shaped, steep-walled amphitheatre carved at the head of a mountain glacier by frost-wedging (plucking loosened blocks at the glacier's bergschrund/headwall) and abrasion; the source area of an alpine glacier, often holding a small lake (tarn) after the ice retreats.
Arête — a sharp, knife-edged ridge formed where two cirques erode headward from opposite sides of a divide and their headwalls intersect, leaving a narrow rock wall between them.
Horn (e.g. the Matterhorn) — a sharp, pyramidal peak formed where three or more cirques erode a mountain from different sides, leaving a steep-sided spire at their common point.
Glacial trough (U-shaped valley) — a valley glacier widens, deepens and straightens a pre-existing V-shaped stream valley into a broad U-shaped cross-section by abrasion and plucking along its full width, often leaving hanging tributary valleys where smaller glaciers join at a higher elevation.
Roche moutonnée — a streamlined bedrock knob, gently abraded/polished on the up-glacier (stoss) side and steep, plucked/jagged on the down-glacier (lee) side, recording ice-flow direction.

1b) Glacial till (depositional) landforms (three)

Ground moraine — a blanket of unsorted, unstratified till deposited more or less uniformly beneath a retreating ice sheet, forming gently rolling, poorly drained lowland topography.
End (terminal/recessional) moraine — a ridge of till bulldozed and dumped at the ice margin where the glacier snout is stationary (ablation balances forward flow) for a period; a terminal moraine marks the ice sheet's maximum advance, recessional moraines mark stillstands during retreat.
Drumlin — a streamlined, elongated hill of compact till, blunt and steep on the up-ice (stoss) side and tapering gently on the down-ice (lee) side, moulded subglacially under actively flowing ice and aligned parallel to ice-flow direction; drumlins occur in swarms (“drumlin fields”) and, per Q1 item 9, are associated with continental (not alpine) glaciation.

2) Figure 4 — Water Related Features (fill in the schematic)

Check: the schematic's printed box labels are blank by design (to be filled in); the reading below follows directly from the diagram's own internal logic — two zones bracket a sloping water-table surface, and the diagram explicitly contrasts an “Unsuccessful well” against a second, deeper well, which only makes pedagogical sense if the unsuccessful well fails to reach the saturated zone while the deeper one succeeds.

Box	Fill-in	Why
Upper hillside box (arrow into subsurface near the house)	Water table	The sloping line separating unsaturated from saturated ground; it is a subdued replica of surface topography, sloping down toward the valley/stream.
Lower hillside box (arrow to where the sloping line meets the surface, feeding the stream)	Spring	The point where the water table intersects the land surface and groundwater discharges naturally, sustaining the stream shown at the base of the slope.
Upper “(Zone)” box, right (arrow to the depth where the unsuccessful well bottoms out, above the water table)	Zone of aeration (unsaturated/vadose zone)	Pore spaces here hold air and only transient moisture; a well that stops within this zone (the “unsuccessful well”) draws no sustained water — that is precisely why it is unsuccessful.
Lower “(Zone)” box, right (arrow to the depth reached by the deeper, successful well, below the water table)	Zone of saturation (saturated zone / unconfined aquifer)	Pore spaces here are completely filled with water; only a well penetrating into this zone can yield a sustained water supply.

Topic: Alpine/continental glacial landform genesis and unconfined groundwater hydrology.

Key relations: Erosional landforms (plucking + abrasion at the ice-rock interface) vs depositional/till landforms (direct dumping of debris carried by or beneath the ice); water table as the top of the zone of saturation, sloping to intersect the surface at springs/gaining streams.

Why this works: Glacial landform identity follows directly from whether ice is removing rock (erosional forms, concentrated at valley heads/bedrock highs) or dumping sediment (depositional/till forms, concentrated at the margin and beneath actively flowing ice); a well's success is purely a question of whether its base lies above or below the water table.

Common pitfall: Listing eskers or kames as “till” landforms — both are ice-contact stratified drift (sorted by flowing meltwater), not unsorted till, so they belong to a separate depositional category from moraines and drumlins.

Source: Marshak, Earth: Portrait of a Planet (glacial landforms); Freeze & Cherry, Groundwater (water table, zone of aeration/saturation, well hydraulics).

Question 5 of 7: Short Answer (Paragraph) and Fill in the Blank

Question 5: Short Answer (Paragraph) and Fill in the Blank (20 marks)

1a) Glacial erosional landforms (three)

1b) Glacial till (depositional) landforms (three)

2) Figure 4 — Water Related Features (fill in the schematic)