Crevasse-squeeze ridge corridors

Diagnostic features of late-stage palaeo-ice stream activity

David J A Evans*, Robert D. Storrar, Brice R. Rea

*Corresponding author for this work

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

A 200-km-long and 10-km-wide linear assemblage of till-filled geometrical ridges on the bed of the Maskwa palaeo-ice stream of the late Wisconsinan southwest Laurentide Ice Sheet are interpreted as crevasse-squeeze ridges (CSR) developed during internal flow unit reorganization, immediately prior to ice stream shutdown. Ridge orientations are predominantly orientated WNW-ESE, with a subordinate WSW-ENE alignment, both indicative of ice fracture development transverse to former ice stream flow, as indicated by NNE-SSW aligned MSGL. Subglacial till injection into basal and/or full depth, mode I and II crevasses occurred at the approximate centreline of the ice stream, in response to extension and fracturing. Landform preservation indicates that this took place during the final stages of ice streaming, immediately prior to ice stream shutdown. This linear zone of ice fracturing therefore likely represents the narrowing of the fast-flowing trunk, similar to the plug flow identified in some surging valley glaciers. Lateral drag between the final active flow unit and the slower moving ice on either side is likely recorded by the up-ice bending of the CSR limbs. The resulting CSR corridor, here related to an individual ice stream flow unit, constitutes a previously unreported style of crevasse infilling and contrasts with two existing CSR patterns: (1) wide arcuate zones of CSRs related to widespread fracturing within glacier surge lobes; and (2) narrow concentric arcs of CSRs and recessional push moraines related to submarginal till deformation at active temperate glacier lobes.

Original languageEnglish
Pages (from-to)40-50
Number of pages11
JournalGeomorphology
Volume258
Early online date29 Jan 2016
DOIs
Publication statusPublished - 1 Apr 2016

Fingerprint

crevasse
ice stream
ice
ice flow
streamflow
glacier surge
Laurentide Ice Sheet
valley glacier
landform
drag
limb
corridor
till
glacier

Keywords

  • Crevasse-squeeze ridge
  • Full depth crevassing
  • Laurentide Ice Sheet
  • Palaeo-ice stream

ASJC Scopus subject areas

  • Earth-Surface Processes

Cite this

Crevasse-squeeze ridge corridors : Diagnostic features of late-stage palaeo-ice stream activity. / Evans, David J A; Storrar, Robert D.; Rea, Brice R.

In: Geomorphology, Vol. 258, 01.04.2016, p. 40-50.

Research output: Contribution to journalArticle

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abstract = "A 200-km-long and 10-km-wide linear assemblage of till-filled geometrical ridges on the bed of the Maskwa palaeo-ice stream of the late Wisconsinan southwest Laurentide Ice Sheet are interpreted as crevasse-squeeze ridges (CSR) developed during internal flow unit reorganization, immediately prior to ice stream shutdown. Ridge orientations are predominantly orientated WNW-ESE, with a subordinate WSW-ENE alignment, both indicative of ice fracture development transverse to former ice stream flow, as indicated by NNE-SSW aligned MSGL. Subglacial till injection into basal and/or full depth, mode I and II crevasses occurred at the approximate centreline of the ice stream, in response to extension and fracturing. Landform preservation indicates that this took place during the final stages of ice streaming, immediately prior to ice stream shutdown. This linear zone of ice fracturing therefore likely represents the narrowing of the fast-flowing trunk, similar to the plug flow identified in some surging valley glaciers. Lateral drag between the final active flow unit and the slower moving ice on either side is likely recorded by the up-ice bending of the CSR limbs. The resulting CSR corridor, here related to an individual ice stream flow unit, constitutes a previously unreported style of crevasse infilling and contrasts with two existing CSR patterns: (1) wide arcuate zones of CSRs related to widespread fracturing within glacier surge lobes; and (2) narrow concentric arcs of CSRs and recessional push moraines related to submarginal till deformation at active temperate glacier lobes.",
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