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EASC 225 (Geomorphology) > Glacial systems post midterm > Flashcards

Glacial systems post midterm Flashcards

1
Q

What is glacier polish?

A
  • an erosional landform caused by glaciers
  • dominant process that forms them is abrasion from basal sliding of sand in contact with the best
  • smooth surface, usually no striations
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2
Q

What are crag and tails?

A
  • erosional landforms caused by glaciers
  • dominant process is abrasion on the stoss side, and deposition of glacial till and sediment on the lee side
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3
Q

What are roche moutonnee?

A
  • erosional landforms formed from glaciers
  • large landforms where glaciers will pluck material on the lee side, and abrade/polish on the stoss side
  • forms ‘uneven triangular shape’
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4
Q

What are cirques?

A
  • erosional landforms created by glaciers
  • glacier will pluck and quarry in the zone of accumulation
  • creates a bowl-like mountain shape
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5
Q

What are tarns?

A
  • lakes that form within cirques
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6
Q

What are aretes?

A
  • erosional landforms formed from glaciers
  • they are the sharp ridges between cirques or valleys
  • result of convergent plucking from adjacent features
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7
Q

What are horns?

A
  • erosional landforms created by glaciers
  • Erosional remnant mountains formed by glacial action at its base
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8
Q

U-shaped valleys indicate…..

A

past glaciation in the area

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9
Q

What are Fjords?

A
  • U-shaped valleys drowned by sea water due to seawater rise.
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10
Q

What is subglacial debris entrainment?

A
  • glacial depositional process
  • debris will be entrained at the base of the glacier, when shear stress from the ice is greater than frictional drag with the bed
  • the debris rich zone at the base of the ice gets mixed up from lateral and vertical migration around obstacles, changes in pressure, and shear deformation
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11
Q

Ice flow can impart ____ on clasts and _____ with distance

A

Ice flow can impart fabric on clasts and comminution with distance

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12
Q

What is fabric? Comminution?

A

Fabric: orientation of clasts long axis parallel to flow

comminution: clasts ground into smaller pieces the father they travel

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13
Q

What is glacial till?

A
  • mostly unsorted, unstratified sediment deposited directly by glacial ice
  • many clast sizes, massive, no layering present
  • till is a type of diamict
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14
Q

What types of till are deposited with active ice?

A
  • lodgment till
  • deformation till
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15
Q

What types of till are deposited with inactive ice?

A
  • melt-out till
  • flow till
  • sublimation till
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16
Q

What is lodgment till?

A
  • process, deposition of till from active ice
  • frictional drag becomes greater than shear stress from moving ice
  • pressure melting releases material from the ice, plasters it on the bed
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17
Q

What are the characteristics of lodgment till?

A
  • well expressed fabric
  • striated clasts
  • shear surfaces
  • fissility (cracks from pressure release)
  • over-consolidation
  • prismatic or columnar weathering structure
18
Q

What is deformation till?

A
  • process, deposition of till from active ice
  • associated with ‘deforming beds’
  • high pressure water systems from basal ice layer saturate and thaw the bed, decreasing the shear strength
  • beds not transported by ice, but deformed from the shear stress and water
19
Q

What are characteristics of deformation till?

A
  • folds, faults, thrusts
  • complex structures
  • undeformed sediment under beds
  • may not have all the indicators of till,
20
Q

What is meltout till?

A
  • deposition of till from inactive ice
  • release of basal debris-rich ice by melting
  • melt from the bottom is called subglacial
  • melt from top is supraglacial
    often deposited in depressions under basal ice
21
Q

What are key characteristics of meltout till

A
  • maintains characteristics of debris-rich basal layer
  • well compacted
  • evidence of running water
  • sandy, stratified intra-till beds
    supraglacial has little to no fabric, no striated/faceted clasts, less well complicated
22
Q

What is flow till?

A
  • deposition of till from inactive glacial ice
  • debris released by ice and redeposited by gravitational slope processes
  • can retain some aspects of debris-rich layer, but altered by slope processes
  • common in valley glaciers
23
Q

What are characteristics of flow till?

A
  • maintains some characteristics of debris-rich layer
  • slope processes may alter fabric and create crude stratification
  • poorly consolidated
  • loose material
24
Q

What are streamlined glacial landforms?

A
  • landforms elongated in direction of ice flow
  • bedforms reflect the organization of bed to shear stress and properties of the bed, like temperature, pressure, sediment load.
  • ex drumlins, flutes
25
Q

What are drumlins?

A
  • glacial landform
  • elongated hills with a steep stoss side, and gently sloping longer lee side
  • ‘tear’ drop shape
    often occurs in swarms, many in a single area
  • largely contain till
  • thought to be formed by dilatancy, where till expands beneath glacial ice, and a mound forms
  • deformable beds are important for drumlins to form!
26
Q

What are flutes?

A
  • glacial landform
  • elongated ridges, lack pronounces
  • less oval than drumlins and flatter too (lower relief)
  • also often occur in swarms
  • usually made of till
  • formed from similar conditions of drumlins or wet till filling cavities on lee side of boulders
27
Q

What are moraines?

A
  • ridges or mounds of glacial material deposited at, or close to, ice margins
  • many different kinds
28
Q

What are rogen moraines?

A
  • ribbed moraines, oriented parallel to the ice terminus
  • very tall, wavy looking
  • depressions often fill with lakes
  • formed from till
  • formed in wet environments, can be ‘reworked’
  • often form with drumlins as well
29
Q

what are terminal moraines?

A
  • material from sub and supraglacial sources that accumulates at the front of and advancing or stable glacier
  • ridge formed parallel to the ice margin
  • terminal moraines will change as a glacier retreats or advances
  • made of lodgement, meltout, and flow tills
  • formed by compressive flow at ice margins that brings subglacial material to the forefront
30
Q

what are till plains or ground moraines?

A
  • landforms associated with glacier deposition, but no prominent bedforms form at the surface
  • from active till or meltout till
31
Q

What are disintegration/stagnation moraines?

A
  • forms from inactive ice, when the deformation of soft substrate materials are made into cavities and crevasses
  • dead ice pushing into till or other soft substrates
  • morphologically, can be uncontrolled (hummocky) or controlled (more linear)
32
Q

What are rhythmites and varves?

A
  • glaciolacustrine sediments, glaciers that form lakes
  • rhythmites are regular series of beds within these glacier lakes
  • varves are season rhythmites, that have ‘stripes’, alternating from dark beds and light beds. Coarser beds produced by rapid melting in summer, fine upper beds deposited in winter
  • beds are typically clay
33
Q

What are supraglacial streams?

A

streams cutting within a glacier, can see from the top of a glacier

34
Q

what are moulins?

A

a circular ‘tunnel’ on a glacier, cutting from the top of the glacier to the bed. point of weakness for the glacier

35
Q

What are englacial channels?

A

horizontal tunnels cutting through the glacier, completely surrounded by ice

36
Q

what are subglacial fluvial processes?

A
  • meltwater processes that bring water to the base of the ice sheet, develop drainage networks and mobilize and deposit sediment under the ice
  • commonly form eskers
37
Q

What are ice-marginal fluvial processes?

A
  • meltwater moving along ice margins, transporting and depositing sediment, but also eroding landscapes.
  • commonly form kame deltas, kame terraces
38
Q

What are proglacial fluvial processes?

A
  • glaciofluvial environment in front of glacier
  • outwash plains and braided channels
  • high energy flows, largely sand and gravel
  • flow variation with seasonal changes (and also changes in thermal regime, mass balance of glacier)
39
Q

How are glaciofluvial sediments characterized?

A
  • better sorted that ice deposited sediments
  • stratified
  • rounded clasts
  • sand and gravel for the most part due to high energy fluvial environment
40
Q
A

EASC 225 (Geomorphology) (5 decks)

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