Glaciers & Landscape

Glacial Studies – two dimensions

- Glacier Dynamics – Glaciology

- Glacier Form – Glacial Geomorphology

Glacier Systems

-systems approach

Input (Mass & Energy) Output (Mass & Energy)

Glacier

Water Vapour Water Ice Rock Detritus Heat

Precipitation Rock Detritus Gravity Solar Radiation Geothermal Heat

Two Subsystems –

- Accumulation

- Ablation

Equilibrium Line (Threshold)

Other Thresholds –

- Glacier Bedrock

- Glacier Atmosphere

Response time – glaciers experience a change of input

Lag before the response becomes discernible at snout

Glacier economics

Balance between rates of input, throughout output

Feedback mechanism

Negative feedback- effects of a change of input are damped down or eliminated

Positive feedback – change is exaggerated or propagated

Scale Awareness

Ideas of Tricart, 1965

Model examples (understanding schemes)

Ice Sheet or Ice Cap

Valley Glacier

SURGING GLACIAL SYSTEM

Landform-sediment assemblages of surging glacier margins in Iceland, Svalbard, USA and Canada

1982-83 surge of variegated glacier of Alaska

Thrust block & Push Moraines

Thrust block moraines – composite ridges & hill-hole pairs

Two ice-marginal settings

- Margins of surging glaciers
- Sub-polar glacier margin in permafrost region

Proglacial thrusting – rapid advance into proglacial sediments
(seasonally frozen, unfrozen & contain discontinuous permafrost)

Proglacially thrust unfrozen materials
Surge margins of Icelandic glacier Bruarjokull & Eyjabakkajokull

Thrust block Moraines – constructional feature produced by surging glacier, sufficient sediment available for glacitectonic thrusting, folding & stacking

Over ridden thrust block moraines

Ice moulded hills in the proglacial forelands of Bruarjokull & eyjabakkajokull – down ice of topographic depressions from which the hills were displaced by thrusting
Surface features – fluted/ Drumlinized
Internal structure – glacitectnized outwash or lake sediments, tops of which modified intoglacitectonite
Ice-moulded hills – overridden thrust block moraines
Thrust block moraine demarcates the former glacier margin during a surge
Prolonged period of modification by over-riding ice – thrust block moraines resemble cupola hills of Aber

Concertina Eskers

Sinuous Eskers and concertina plan-form eskers
(Knudsen) – Concertina eskers are produced by shortening of pre surge, sinuous eskers, deformed by extreme tectonic activity
Vertical thickening – concertina plan form

Crevasse – squeeze ridge

Bruarjokull & eyjabakkajokull, Iceland
Trapridge Glacier & donjek Glacier – in Yukon territory & from Svalbard
Tectonics experienced during surge – glacier is highly fractured & crevasses may extend to the glacier bed

Flutings

Forelands of many glaciers
Evidence of rapid advances over substantial distances foreland of Bruarjokull (regularly spaced parallel sided flutings)
Numerous boulders with short sediment prows/ flutes on their down-flow sides interpreted as ploughs/ incipent flutes produced by boulders embedded in glacier sole
Elongation of these flutes suggest, formed during a single flow event when basal water pressures & degree of ice-bed coupling remained shorter & much less uniform in long section
Flutings & crevasse squeezed ridges – aspect & subglacial geomorphology of surging glaciers

Thrusting/ squeezing.

Zone of thrusting in the snout, lifted from the bed thrusting in surging glaciers
Supraglacial sediments
Low relief hummock moraine comprising inter bedded sediment gravity flows & crudely bedded sediment sediments – small ridges, thrust intersected the bed

Hummocky moraine

Subsequent ice-stagnation of widespread & effective transportation of large volumns of material

Lowland surging glaciers – thrusting is dominant process in transporting large volumns of debris-rich stagnant ice preserved from a previous surge, producing thick sequences of debris rich & debris-covered ice in surging snout

Landform assemblage – Hummocky moraine
Kettle & kames Topography

Differential form of overridded thrust block moraine by extensive evidence of on going meltout of buried ice

Ice-cored outwash & glacilacustrine sediments

Variegated glacier surge – outbursts of supraglacial water

Landform model for surging glacier

Based on combination of observations from contemporary surging glacier margins & published literature
Geomorphic & sedimentological signature of surging

Geomorphology – 3 overlapping zones

· Outer Zone: of thrust block & push moraine
Weakly consolidated pre-surge sedimets
Structurally – major thrust block moraine restricted to topographic depression, large enough to collect sufficient sediment during the quiescent phases.
· Intermediate zone (zone B) – patchy hummocky moraine located on the down-glacier sides of topographic depression, dumped on ice proximal slopes of thrust block & push moraine.

SURGING GLACIER SYSTEM

Landform-sediment assemblages of surging glacier margins in Iceland, Svalbard, USA and Canada

1982 surge of Variegated Glacier of Alaska

Thrust Block and Push Moraine

Thrust Block moraines – composite ridges & hill hole pairs

Two ice-marginal settings

- Margins of surging glaciers

- Sub-polar glacier margins in permafrost terrain

Proglacial thrusting – rapid advance into proglacial sediments

(seasonally frozen, unfrozen or contain discontinuous permafrost)

Proglaciacially thrust unfrozen materal – surge margins of Icelandic Glacier (Bruarjokull & Eyjabakkajokull)

Thrust block moraines – constructional feature produced by surging glacier, sufficient sediment available for glacitectonic thrusting, folding and stacking

Over-ridden thrust block moraines

Ice-moulded hills in the proglacial forelands of bruarjokull and Eyjabakkajokul – downice of topographic depressions from which the hills were displaced by thrusting

Surface features – fluted/drumlinized

Internal structure – glacitectonized outwash or lake sediments, tops of which modified into glacitectonite

Ice-moulded hills – over-ridden thrust block moraines

Thrust block moraines demarcates the former glacier margin during a
surge

prolonged period of modification by over-riding ice – thrust block moraines resemble cupola hills of aber

Concertina Eskers

Sinuous eskers and concertina plan-form eskers

(Knudsen) – concertina eskers are produced by shortening of pre-surge sinuous eskers deformed by extreme tectonic activity & vertical thickening – concertina plan form

Crevasse-squeezed ridge

Bruarjokull & eyjabakkajokul, Iceland

Trapridge glacier & donjek Glacier – Yukon Territory & from Svalbard

Tectonics experienced during surge – glacier is highly fractured and crevasses may extend to the glacier bed

Flutings

- Forelands of many glaciers

- Evidence of rapid advances over substantial distances foreland of Bruarjokull (regularly spaced parallel-sided flutings)
- Numerous Boulders with short sediment prows/flutes on their downflow sides interpreted as ploughs/incipent flutes produced by boulders embedded in glacier ice
- Elongation of the flutes suggest, formed during a single flow event when the basal water pressures & degree of ice-bed coupling remained shorter & much less uniform in Section
- Flutings & crevasse squeezed ridges – aspect of subglacial geomorphology of surging glaciers

Thrusting & squeezing

Zone of thrusting in the snout, lifted from the bed, thrusting in surging glaciers, supraglacial sediment

Low-relief hummocky moraine comprising interbedded sediment gravity flows & crudely bedded stratified sediments

Small ridges, thrust intersected the bed

Hummocky moraine

Subsequent ice-stagnation of widespread & effective transportation of large volumns of material

Lowland surging glaciers – thrusting is dominant process in transporting large volumns of debris into englacial and supraglacial position

Successive surges – over-riding, overthrusting, incorporation of debris rich stagnant ice, preserved from a previous surge, producing thick sequences of debris rich & debris covered ice in surging snout

Landform assemblage

Hummocky moraine ridge

Kettle & kames topography

Differentiated from over-ridden thrust block moraine by extensive evidence of on-going meltout of buried ice

Ice cored outwash & glacilacustrine sediments

Variagated glacier surge – outbursts of supraglacial water

Landsystem model for surging glacier

Based on combination of observations from contemporary surging glacier margin & published literature

Geomorphic & sedimentological signature of glacier

Geomorphology – 3 overlapping zones

· Outer zone : of thrust block & push moraines weakly consolidated presurge sediments

Structurally – major thrust block moraine restricted to topographic depression large enough to collect sufficient sediment during the quiescent phases

· Intermediate Zone: patchy hummocky moraine located on the down-glacier sides of topographic depression, draped on ice proximal slopes of thrust block moraines & push moraines

Hummocky moraines – intensely glacitectonized fine grained stratified sediments & diamictions or poorly sorted gravels – products of thrusting, squeezing & bulldozing

· Inner Zone – subglacial deformation tills & low amplified flutings produced by sub-hole deformation during the surge

Crevasse-squeezed ridges, documenting the filling of basal crevasses, concertina eskers

Palimsets & outer surges (overridden moraines)

Proglacial outwash fans & streams (ice-cored collapsed outwash)

Ponded topographic depression on the foreland (collapsed lake

Plains)

GEOMORPHOLOGY ZONATION MAP OF EYJABAKKAJOKULL, ICELAND


CONCERTINA ESKER


CREVASE SQUEEZE RIDGE

GLACIATED VALLEY SYSTEMS

Incorporate icemarginal features including supraglcial, subglacial, progracial, (fluvial, glaciofluvial), periglacial & paraglacial landsystems

Two Factors:
- Influence of topography on glacier morphology, sediment transport paths and depositional basin

- Importance of debris from supraglacial sources in the glacial sediment budget

Clean glaciers – glaciers with limited supraglacial debris
Debris – covered glacier – glacier with substantial debris cover in ablation zones

Sediment sources

Process involved in delivering debris tto glacier surface – debris flow, snow avalanches, rockfalls, rock avalanches

Tectonically active regions – earthquake generated rock avalanche

Glaciers with high debris soncentration – rockfall rates are high, snowfall is low

Sediment Transport pathways

2 sediment transport pathways (Boulton)

1. actice subglacial transport
2. passive supraglacial or englacial transport
   

active because in basal shear zone, high particle collision undergoes significant abrasion, fracture or communition

sediment in upper layer – little modification, retains characteristics of parent debris

Moraine Classification

(By Eyles & Rogerson)

– based on relationship between debris supply and morphological development of the moraine

1. Ablation dominant moraine (AD) – which emerge at the surface as a result of the melt out of subglacial debris
2. Ice-stream interaction moraine (ISI) – which find immediate surface expression downstream from glacier confluences, often by merging of two supraglacial lateral moraine
3. Avalanche type (AT) moraine – which are transient features formed by exceptional rockfall events onto a glacier
   

Dynamics of Debris covered glaciers

Thin debris cover – enhances ablation due to reduced albedo & increased absorption of long & short wave solar radiation

Thick cover – reduces ablation (due to low thermal conductivity

LAND SYSTEMS OF GLACIAL DEPOSITION

Ice marginal moraines & related landforms

Processes of moraine formation

Moraine formation at glacial margin with limited supraglacial debris

- Pushing (margin in buried by glacifluvial deposits/ Debris flow)

- Dumping of supraglacial debris

- Squeezing (fine grained saturated sediment present at the margin

Thrust moraine

Glaciers in contact with thick unconsolidated sediments such as glacimarine clays and silts

Moraines <10m>

Resistant crystalline rock

Lateral moraines and boulder lines

Lateral-Terminal Moraine Complex

Lateral Moraines – extend from equilibrium line as continuous sharp crested ridges increasing down glacier in cross section

Upper ablation Zone – moraine have little distal slope, a debris veneer accreted onto the valley wall

Down valley – moraines separated from valley wall forming lateral moraine trough

Lateral – frontal moraine – as debris fall, slumps, slides or flows down the ice edge and accumulates around glacier margin

Ice-proximal parts of lateral-frontal moraine – structurally complex because of widespread collapse & reworking following removal of ice support

Breach-lobe moraines

Inset loops or lobate moraines

Multi-lobed moraines – terminus morphology to a long term expansionary tendency and repeated breaching of main moraine barrier

Explanation based on morphology of glacier e.g. HATUNRAJU of Peru

Ablation Valleys – infills in lateral moraine trough

Separate lateral moraines from valley side slopes and act as gutters trapping slope debris transported by processes including rock fall, debris flow, snow avalanche, & fluvial transport

Within valley Asymmetry of lateral moraines

Large moraine volume on one side of the valley than on other

Causes of asymmetry

- Larger moraine occur on valley sides with extensive rock walls – increase debris supply

- Lateral moraine formed by pushing and thrusting of pre-existing material within valley asymmetry – result from differences in thickness & type of sediment on the foreland

- Cross valley differences in lithology or structure – influence debris supply to surface or bed

- Asymmetry may occur due to difference n glacier dynamic on either side of the valley.

Sub glacial sediments & Landforms

- Ice moulded bedrock – occupy upper part of former valley glaciers

- Striated roche motonees, whalebacks, ovedeepened rock basins – abrasion features

- Downvalley – rock outcrops, downstream of roche moutonees (lee side cavity frills)

Over consolidated lodgement or high strength deformation till – matrix support, fissile structure, abundant faceted striated clasts

Fluted moraines – down glacier, low preservation, may not survive more than few decades

Facies of Glacier retreat

Recessional or hummocky moraine

- Mark positions of annual readvances or more significant longer turn advances of the margin

- Common in low relief mountains

Hummocky moraine – products of widespread glacier stagnation (common in Scotland)

- Polygenetic

- Consisting of recessional moraines forming converging cross valley pair

- Flow-parallel drumlins and flutings

- Non-aligned mounds and ridges, recording uncontrolled ice-marginal deposition

Till sheets

3 facies of deposition based on association between activity of terminus, thickness of supraglacial cover and reworking of meltwater

Facies 1 – thick reworked accumulation of supraglaciall till deposited by back wasting & decay of melting ice cores buried beneath thick debris cover

Stationary ice terminus, predominance of meltwater process results in a chaotic disintegration of topography, final product does not reflect geometry of ice margin (Eyles)

Facies 2 – dispersed bouldary veneer by dumping from a retreating terminus, downglacier lineated pattern reflected deposition focused by structures such as gullies in the ice front. Thin debris cover, no relief inversion associated seasonal dump moraine – internal bedding due to gravity sorting

Facies 3 – supraglacial till complex comprising of interfingering lensate horizons of supraglacial meltout till & glaciofluvial sediment – areal extent greater at inactive, low gradient termini where meltwater streams & ponds occur within ice-cored terrain – distribution & relative development of facies may aid in reconstruction of ice margin dynamics during glacier retreat

Evolution of downwasting, debris cover glacier termini in Iceland – documented by kruger

Final deposition assemblage – low relief, hummocky topography underlain

Medial moraines

Supraglacial debris on valley glaciers, delievered to terminus – medial moraine

Seldom preserved after deglaciation

Contain small amount of debris & tend to undergo considerable reworking during glacier ablation

Deposition – longitudinal bands of facies 1 & 2

Rock Glaciers

Tongue like or lobate masses of ice & coarse debris that flow downslope by internal deformation

Ridges, furrows, lobes on surfaces, steep fronts down which debris collapses & overridden by advancing mass

Twofold genetic classification

- Periglacial rock glacier involve the slow deformation of ground ice below talus slopes

- Glaciel rock laciers

Form by the progressive burial and deformation of a core of glacier ice by a thick boundary debris mantle

In mountain environment

Rock, snow & ice are delivered to the base of slopes by avalanches & other mass movement processes

- Negligible rock component – clean glaciers will form where snow and ice con survive ablation over the balance year

- Snow & ice component zero – talus slope

- Rock component relatively high, debris accumulates as a lag on the ablation zone of the dirty ice mass – debris covered glacier

- Rock component much higher, avalanche snow and ice will occur as isolated but deformable lenses within a talus – rock glacier (g high mountain environment as Khumbu Himal, Karakoram, Lahul Himalaya)

Dependant on climate

Decreases precipitation/increase temperature- increased proportion of rock, formation of rock glacier

Glacial retreat – active rock glaciers as head of former rock glacier forms

Rock-glacierized moraines of Canadian Arctic

Coupled Ice Margin

Efficient transfer of sedimets between glacier & proglacial fluvial system

e.g. Humid mountain ranges of Alaska & new Zealand, from last glaciation in New Zealand & southern South America

Decoupled Ice Margin

In smaller glacier & arid mountain ranges, inefficient outwash discharge from glacial to fluvial systems, examples in Ngozumpa Glacier (Nepal), Hatunraju Glacier (Peru), Miage Glacier (Italy)

INTRODUCTION TO GLACIAL LANDSYSTEMS

Land systems concept – popularized by Commonwealth Scientific and Industrial Research Organization for mapping large spacely populated areas of Australia – 1940s

A recurring pattern of topography, soils and vegetation – part of land system

Preliminary stages of mapping – topography or geomorphology

Land system – divided into smaller components called units or facets and elements

Development history of terrain mapping:

Reference: Mabbutt, Mitchell, Ollier, king, Cooke & Doomkamp

Glacial Land systems

Mapping of Glacial Terrain – grouping of landforms according to common origin & age

Glacial stratigraphy (a landscape as a series of layer)
- a prerequisite for studing glacial geomorphology

3 main systems were identified

- Till plain Landsystem – subglacially deposited tills & drumlinized surface
- Glaciated valley landsystem – materials produced by melting glacier ice
- Fluvioglacial & ice-content deposit landform – landforms & sediments that are ice contact, fluvioglacial origin

For a Glaciated Valley Land system

Elements – individual landforms at large scale e.g., drumlins, flutings, eskers, kames, terraces, moraines
Units – features which constitute relatively homogenous tracts of land distinct from surrounding surface (e.g. drumlin/ fluting field)

GLACIAL SYSTEM

GLACIAL VALLEY SYSTEM

SUPRAGLACIAL LANDSYSTEM

ICE MARGINAL TERRESTRIAL LAND SYSTEMS: SVALBARD POLYTHERMAL GLACIERS

Geomorphology and sedimentology of receding Svalbard Glacier

Ice Push versus thrusting of sediment

Moraine mound complex – huge moraine systems in front of receding Svalbard Glacier

Morphology: arcuate belts of aligned hummocks or mounds comprising of morphological types
· Linear ridges – 100 m long
· Short crested ridges – several metres long
· Near conical mounds – reaching elevations of several metres

Ice proximal rectilinear or curvilinear slopes with consistent angle of around 30*, irregular distal slopes that are commonly steeper

Thrusting & stacking of thick sediment wedges – survival of initial moraine morphology

Other constructional Landform

Linear debris stripes – folding of supraglacially derived layers in the ice derived from folded stratified layers and emerge at the glacier surface as medial moraines as a result of ablation near the snout. Regular stripes of angular debris extending for considerable distances across the proglacial area. Debris stripes recognized by their angular unilithological nature and lack of fine matrix

Foliation-parallel layers – basally derived debris. Surge type Kongsvegen, Vestre Lovenbreen. Result of melting of ice core – mechanism à lateral compression of ice leads to the development of a transposition foliation parallel to the flow combined with the incorporation of basal debris-rich ice or soft basal sediment infold complex

Geometrical ridge network – created when both longitudinal and tranverse debris accumulates, meltout of glacier and become superimposed

Flow parallel ice structures – Marthabreen

2 types : Longitudinal sediment structures – ridges of sand and gravel, sub parallel to foliation fill consists of fine sand and gravel

Longitudinal ridge accumulations – larger ridges, occur downstream of sediment structures

Streamlined ridges – forefield of Austre & middle lovenbreen – elongated in the direction of glacier flow at glacier margin, emerge from beneath receding glacier margin

Landsystem model for Svalbard Glacier

3 zones within its forefield

• Outer moraine ridge – arcuate ridges rsing steeply from surrounding topography, ice cored, product of permafrost deformation, englacial or proglacial thrusts
• Moraine-mound complex – arcuate belts of aligned hummocks, include linear ridges, short crested ridges, near conical mounds. High friction at decollement surface –

thrust dominated moraine complex (Comfortlessbreen, Uverbreen, Krone Breen)
permafrost areas – proglacial deformation (erikbreen, Usherbreen)
low friction at glacier bed – polyphase folding (sefstrombreen)

• Inner Zone – between moraine mound complex and modern glacier snout. Foliation parallel ridges, supraglacially derieved stripes of debris, geometrical ridge networks, streamlined ridges, flutes.
  

	GLACIAL LANDFORM	LOCATION
Ice margin terrestrial land systems: sub polar glacier margins of the Canadian and Greenland high arctic	Valley Glaciers	Vestre lovenbreen, Midtre Lovenbreen, Austre Lovenbreen, Pedersenbreen, Botnfjellbreen
	Valley glaciers with prominent outer moraine ridge, with moraine mound complexes, glacifluvial facies and linear debris dtripes	Midtre Lovenbreen, Austre Lovenbreen
	Linear debris stripes	Austre Broggerbreen
	Moraine Mound Complex (hummocky moraine)	Kronebreen
	Group of small flutes	Midtre Lovenbreen

LOCATION OF SVALBARD ARCHIPELAGO

ORIGIN OF STRUCTURE IN SVALBARD GLACIER

LAND SYSTEM MODEL OF SVALBARD POLYTHERMAL GLACIER

MORAINE MOUND

By NEIL F. GLASSER AND MICHAEL J. HAMBREY

LANDFROMS FORMED BY GLACIAL EROSION

LANDFORM	DESCRIPTION
Abrasion by glacier ice - streamlined relief forms (mm to 1000 km)
Areal Scouring	Regional expenses of lowland Bedrock, upto 1000s KM in extent, scoured by Ice. Sometimes contain sets of parallel groves and bedrock flutes
Glaciated Valley	Glacial trough, the floor of which is above sea level, Often U shaped
Fjord	Glacial trough, the floor of which is below sea level,. Often U shaped
Hanging Valley	Tributary Valley whose floor sits above the floor of the trunk valley
Breached watershed	Col abraded by a valley glacier spilling out of its confining trough
Dome	Dome-shaped structure found in uniform bedrock where ice has abraded an obstacle to leave a smoothed rock hillock that has been subject to exfoliation
Whaleback or rock drumlin	Glacially streamlined erosional eature 100-1000 m long intermediate in size between a roche moutonee and flggberg
Striation	Scratch on Bedrock or clast made by ice (or other geomorphic agent such as landslides, techtonic disturbance and animals)
Polished surface	Bedrock surface made shiny by a host of tint scratches scoured by finely grained clasts
Groove	A furrow cut into bedrock by fragments of rocks held by advancing ice
Plastically moulded forms (p-forms)	Smooth and complex forms on rock surface. They include Cavetto forms (channels on steep rock faces) and grooves (on open flat surfaces). Sichelwannen and Nye channels (curved and winding Channels) are also p-forms bur probably produced mainly by eltwater erosion
Abrasion and rock fracturing by glacir ice - partly streamlined relief forms (1m - 10 km)
Trough head	Steep rocky face at the head of many glaciated valleys and fjords
Rock or valley Step	Bedrock step in the floor of glacial troughs, possibly where the bedrock is harder and often where the valley narrows
Riegel	Low rock ridge, step or barrier lying across glaciated valley floor
Cirque	Steep walled semi circular recess or basin the bountain
Col	Low pass connecting two cirques facing in opposite directions
Roche Moutonnee	Bedrock feature, generally less than 100 m long, th elong axis of which lies parallel to the direction of ice movement. The up-ice (stoss) side is abraded, polished and gently sloping and the down-ice (lee) side is rugged and steep
Flyggberg	Large (>100 m Long) streamlined bedrock feature, fformed through erosion by flowing ice. The up-ice (stoss) side is polished and gently sloping, whereas the down-ice (lee) side is rough, irregular and steep. A flyggberg is a large scale roche moutonnee or whaleback.
Crag and tail or leeside cone	An assymetrical landform comprising a ruged crag with a smooth tail at its lee
Rock crushing - non-streamlined relief forms (cm to 10s cm)
Lunate Fracture	Crescent shaped fractures with the concavity facing the direction of Ice Flow
Crescentic Gouge	Crescent shaped fractures with the concavity facing away from the direction of Ice Flow
Crescentic Fracture	Small, crescent shaped fractures with the concavity facing away from the direction of Ice Flow
Chattermarks	Crescent shaped friction cracks on bedrock, produced by the juddering motion of moving ice
Erosion by glacier ice, frost shattering, mass movement - residual relief forms (100m to 100Km)
Arete	Narrow, sharp-edged ridge seperating two cirques
Horn	Peak formed by intersecting walls of three or more cirques. An example is the Matterhorn
Nunatak	Unglaciated island of bedrock, formerly or currently surrounded by ice