Glaciers M/C Flashcards by Lydia Serbanescu

Which of the following glacier types is most likely to form a series of valley glaciers from a central ice accumulation area?

A) Cirque glacier
B) Ice field
C) Piedmont glacier
D) Tidewater glacier

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A glacier with a terminus in a lake that regularly calves icebergs is classified as a:

A) Ice shelf
B) Ice cap
C) Piedmont glacier
D) Tidewater glacier

D - tidewater glaciers end in large bodies of water and produce icebergs

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Which condition would increase basal shear stress (𝛕), and therefore glacier movement?

A) Lower slope angle and thinner ice
B) Higher slope angle and thicker ice
C) Colder ice and lower slope angle
D) Warm ice and low ice density

B - shear stress increases with both ice thickness and surface slope

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What best describes the thermal regime of a cold-based glacier?

A) Contains water throughout; promotes basal sliding
B) Warm at base; promotes meltwater channel formation
C) Frozen to its bed; minimal basal movement
D) Forms in maritime climates with heavy snowfall

C - cold-based glaciers are frozen to their bed and don’t slide much

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The zone above the Equilibrium Line Altitude (ELA), where snow survives summer melt, is called:

A) Ablation zone
B) Firn line
C) Accumulation zone
D) Mass balance zone

C - this is where more snow is gained than lost annually

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What kind of landform is created when subglacial meltwater carves channels in the bedrock beneath the glacier?

A) R-channel
B) N-channel
C) Moulin
D) Kame delta

B - N-channels are cut into bedrock or sediment at the glacier base

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Which process allows ice to flow past obstacles by melting under pressure and refreezing on the lee side?

A) Basal slip
B) Regelation
C) Creep
D) Bed deformation

B - regelation is a pressure-induced melting and refreezing, helping ice navigate around obstructions

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Which form of till is deposited directly by glacial ice under pressure, producing dense, fine-grained material?
A) Lodgement till
B) Flow till
C) Melt-out till
D) Glaciofluvial till

A - lodgement till is dense and deposited under high pressure beneath ice

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A drumlin is best described as:

A) A stratified ridge of glaciofluvial sediment formed in ice-contact tunnels
B) A symmetrical hill with the long axis oriented across ice flow
C) An elongated hill of glacial debris with a steep stoss side and gentle lee side
D) A fan-shaped outwash plain composed of sorted sands and gravels

C - drumlins are streamlined hills aligned with ice flow, with an asymmetrical profile

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Which feature indicates a glacier in retreat based on the shape of its terminus?

A) Steep terminus with advancing moraines
B) Moderate slope at the toe
C) Gentle, sloping terminus partly buried under debris
D) Bergschrund near the toe of the glacier

C - retreating glaciers leave behind gentle toes, often buried by stagnant ice and debris

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Which of the following best describes lodgement till?

A) Loosely packed, angular debris dropped from melting supraglacial ice
B) Sorted, stratified sands and gravels deposited by meltwater
C) Dense, compact material deposited under pressure beneath a moving glacier
D) Till deposited directly into standing water forming varved layers

C - lodgement till is dense and compacted beneath sliding glacier ice

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Which process is primarily responsible for the formation of melt-out till?

A) Subglacial water erosion
B) Direct melting of ice containing debris
C) Flowing meltwater streams sorting sediments
D) Bed deformation beneath stagnant ice

B - melt-out tills form as debris is released from melting glacier ice

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What distinguishes flow till from other types of till?

A) It is deposited directly from the base of a glacier
B) It is reworked by meltwater and sorted into coarse and fine layers
C) It is formed by gravitational processes and shows slope-oriented fabric
D) It is the densest form of till, deposited beneath a glacier under pressure

C - flow tills are redistributed by gravity and show slope-oriented fabrics, not ice movement patterns

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What type of till is most associated with supraglacial debris melting out onto the ground?

A) Lodgement till
B) Subglacial melt-out till
C) Supraglacial melt-out till
D) Deformation till

C - supra glacial melt-out tills are coarse, angular and loosely packed

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Which feature would most likely indicate a deformation till?

A) Stratified structure and rounded clasts
B) Dense till with visible folds, thrusts, or undeformed blocks
C) Smooth, laminated layers from lake deposition
D) Randomly oriented, unsorted clasts with angular edges

B - deformation tills often exhibit internal structures like folds and faults

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A till fabric aligned with ice flow direction is most commonly observed in:

A) Flow till
B) Lodgement till
C) Supraglacial melt-out till
D) Glaciolacustrine clay deposits

B - lodgement tills often show fabrics aligned with glacial movement

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What best differentiates primary till from secondary till?

A) Grain size distribution
B) The environment in which deposition occurs
C) Whether the material has been reworked post-deposition
D) The presence of meltwater structures

C - primary tills are deposited directly from the ice and secondary tills are reworked sediments

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Which till is formed by the release of sediment into depressions and is loosely packed and angular?

A) Flow till
B) Melt-out till
C) Supraglacial melt-out till
D) Lodgement till

C - supra glacial melt-out tills are usually angular and poorly packed due to direct melting

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A till layer with massive texture, angular clasts, and no stratification is most likely:

A) A glaciofluvial deposit
B) Glaciolacustrine sediment
C) Lodgement till
D) Ablation till

D - ablation tills is often unstratified, massive and dropped by melting ice

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Which of the following would not be a reliable way to distinguish between till types?

A) Fabric alignment
B) Degree of sorting
C) Grain size
D) Rock mineralogy

D - mineralogy may vary with local geology but doesn’t indicate till type

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A deposit is massive (no visible layering), contains a mix of clay, sand, gravel, and boulders, with angular clasts and no sorting. What’s the most likely depositional process?

A) Glacial ice
B) Glaciofluvial
C) Lacustrine
D) Aeolian

A - classic description of till, deposited directly by glacial ice

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A sediment core from a basin reveals alternating light and dark, thin, horizontal layers. The coarser layers are lower in each couplet, and the material is mostly fine silt and clay. What process is responsible?

A) Subglacial deformation
B) Melt-out from supraglacial ice
C) Seasonal lacustrine deposition
D) Subglacial tunnel erosion

C - varves (seasonal couplets) are hallmarks of glaciolacustrine deposition

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You observe well-sorted sands and gravels, organized into horizontal beds with some cross-bedding and occasional ripple marks. What depositional process is most likely?

A) Direct ice deposition
B) Glaciofluvial stream activity
C) Subglacial melt-out
D) Glaciomarine dropstone sedimentation

B - cross-bedding and sorting = classic glaciofluvial stream deposits

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A field site reveals a ridge made of stratified sands and gravels, some clasts are rounded, and the deposit follows a sinuous path, even crossing small valleys. Which of the following best explains its origin?

A) Ice-contact supraglacial melt-out
B) Kame terrace
C) Subglacial stream in an R-channel
D) Lodgement till

C - this is describing an esker, formed by subglacial meltwater in an ice-walled tunnel (R-channel)

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A fine-grained, laminated deposit is found far from the glacier margin. It contains occasional large, angular clasts that seem to have dropped in randomly. What is the most likely explanation? A) Till with meltwater lenses B) Ice-rafted debris in a lacustrine or marine setting C) Outwash sediment with debris from an esker D) Flow till overlying lodgement till

B - this is dripstone sedimentation in a glaciolacustrine or glaciomarine environment

A deposit of coarse gravel and cobbles is observed near a former ice margin. It has moderate sorting, faint horizontal bedding, and was deposited in front of a terminal moraine. What process likely caused this? A) Lodgement under glacier pressure B) Proglacial braided stream deposition C) Subglacial deformation D) Sublimation till melt-out

B - classic outwash plain (sander) deposited by braided glaciofluvial streams

You examine a deposit composed of loosely packed, angular boulders and sand sitting on top of older stratified layers. There’s no evidence of stream reworking. What’s the most likely depositional environment? A) Ice contact glaciofluvial fan B) Melt-out till from supraglacial debris C) Lodgement till D) Subglacial till plastered by pressure

B - coarse- angular, unmodified = supraglaical melt-out till

A geologist maps a low-relief plain with unsorted sediment, no bedding, and an erratic mix of clast sizes and types. The clasts are often striated or faceted. What’s the best interpretation? A) Deposited by glaciofluvial channel during outburst flood B) Formed in a glacial lake delta environment C) Subglacial till deposited by moving glacial ice D) Laid down by lacustrine density underflows

C - ground moraine, composed of subglacial till, likely lodgement till

Which of the following environments would most likely produce a deposit with fine-grained laminated sediments and no coarse material present? A) Kame delta B) Supraglacial stream channel C) Distal glaciolacustrine basin D) Proglacial outwash fan

C - fine, laminated, no coarse = distal glaciolacustrine setting

You observe sorted, stratified sands and gravels with deformation structures and some angular fragments. It's located next to a former ice margin. What best explains its formation? A) Lodgement till from a warm-based glacier B) Ice-contact stratified drift reworked by meltwater C) Deformation till formed from high shear stress D) Lacustrine deposition near a subaqueous fan

B - that mix of sorting and deformation = ice-contact stratified drift

What kind of thermal regime and bed condition would most likely cause a surge?

a warm-based glacier with sudden meltwater lubrication

What’s the most common sediment characteristic of a glacial till?

massive bedding - unsorted, unstratified

This deposit is stratified, moderately well-sorted, mostly sand and gravel. It formed from flowing meltwater. What process?

This is likely outwash or part of an esker.

Which deposit is layered with alternating coarse (summer) and fine (winter) beds?

Glaciolacustrine varves reflect seasonal deposition in lakes.

What does a steep, clean glacier terminus with little debris suggest about the glacier’s mass balance?

Steep = actively pushing forward. Advancing glacier!

You find angular, poorly sorted debris sitting atop older deposits with no evidence of water sorting. What is this most likely?

Angular, coarse, loose = supraglacial melt-out.

What does the term “lodgement till” imply about how the sediment was deposited?

Lodgement till forms when debris is plastered under pressure from basal ice

Which type of crevasse forms due to longitudinal extension (stretching)?

Extension = transverse crevasses

Which environment: Very fine, well-stratified clay with rhythmic bedding and occasional dropstones?

glaciomarine OR distal lacustrine dropstones = marine most likely

How do eskers form?

They’re deposited in subglacial/englacial meltwater tunnels, especially R-channels.

What does “regelation” describe in glacier motion?

Melting and refreezing at pressure changes

What term describes the point on a glacier where annual accumulation equals ablation?

Equilibrium Line Altitude (ELA)

Which till type forms from gravity-driven debris flows at the glacier margin?

flow till - they're messy and slope-driven

What would you expect in a glaciofluvial deposit near the glacier terminus?

Better sorting and rounding than till, but not perfectly sorted.

A deposit with folded layers, faults, and densely packed clasts shows what type of till?

deformation till!

Which glacier type flows into the ocean and produces icebergs?

tidewater glacier

A hummocky terrain with kettles and kames suggests what kind of deposition?

Disintegration or hummocky moraine - specifically linked to melting stagnant ice

You find a deposit with a strong alignment of clasts parallel to former ice flow. What does this suggest?

till fabric in lodgement till or deformation till - clasts tend to align due to ice stress or flow

How can you distinguish glaciolacustrine from glaciofluvial sediments?

lacustrine = fine + stratified fluvial = coarser, same sorting

Which flow type occurs when dense, sediment-laden meltwater sinks into a lake?

Hyperpycnal flow - happens with sediment laden meltwater is denser than lake water and sinks

What kind of glacier movement is dominant in cold-based ice?

creep - since it's frozen to the bed, it can't slide - just internal deformation

You find a laminated deposit with rhythmites and occasional large clasts embedded in fine sediments. There are no nearby river channels. What two depositional processes might be at work here?

glaciomarine deposition, ice-rafting of dropstones

Which till type forms beneath a glacier due to frictional drag exceeding basal shear stress, leading to sediment being plastered onto the bed?

lodgement till

What glacial feature often indicates a recession pause rather than the full advance of a glacier?

recessional moraine (technically also an end moraine)

What term describes a situation where glacial meltwater enters a lake and has the same density as lake water, causing horizontal spreading?

homopycnal

Which erosional landform has a smooth stoss side, a plucked lee side, and forms in bedrock under warm-based ice?

Roche Moutonnée

If you find stratified, angular, poorly sorted deposits that are folded and jumbled near the margin of former ice, what depositional environment is most likely?

deformation till, deposited by glacial ice

What’s the dominant transport pathway for debris incorporated by supraglacial rockfall in an alpine environment?

supraglacial transport

Why are cold-based glaciers generally poor at eroding bedrock?

they're frozen to the bed!

What’s the best field evidence that a glacier was previously advancing across a region?

terminal moraine

A series of crescent-shaped ridges oriented perpendicular to former ice flow, commonly found in broad valleys, suggest what landform?

Rogen moraine - they're sinuous, transverse ridges usually formed beneath stagnant or slow-moving ice, often associated with frozen/thawed beds

Which of the following is not typically composed of ice-contact stratified drift? A) Esker B) Kame terrace C) Lodgement till D) Kame delta

Which characteristic best distinguishes ice-contact stratified drift from outwash plains? A) It contains larger boulders B) It is deposited in a lake C) It forms without glacial ice nearby D) It deforms as ice melts away

D - outwash forms beyond ice margins on stable ground, whereas ice-contact drift can slump or deform when underlying/adjacent ice melts

What does the presence of stratification in glacial sediment usually tell you? A) It was deposited by glacial ice alone B) It was sorted by water C) It came from a subglacial deformation event D) It has high clay content

Is all ice-contact stratified drift an ice-contact deposit?

Yes, it's a subtype of a larger category

What makes stratified drift different from till?

till = unsorted, direct ice. stratified drift = water-sorted (meltwater involved)

What causes deformation/collapse in ice-contact stratified drift?

collapse often happens when the supporting glacial ice melts, leaving sediment with no structure. water places the sediment, ice supports it - when ice melts, it slumps