Applied Glaciology

Ice Excavation in an Open Ice Pit

Posted by William Colgan on September 24, 2014
Applied Glaciology, New Research / No Comments

I have a paper in this month’s issue of the Journal of Cold Regions Engineering that examines the ice excavation required to establish and maintain an open ice pit. Excavating an open ice pit is a very non-linear applied glaciology problem, as the excavation of ice from an open ice pit enhances subsequent ice flow into the open ice pit. This is because ice velocity is very sensitive to changes in ice geometry, with third and fourth order dependencies on ice slope and thickness respectively! The paper examines scenarios based on excavating an open ice pit on the Greenland ice sheet margin that extends 1000 m into the ice sheet, with a 200 m high ice wall. That is the approximate dimension of the Isua Prospect, Greenland, which is projected to excavate about 36,000,000 tonnes of glacier ice per year.

Working with such unnatural combinations of ice slope and ice thickness compels you to reconsider fundamental principles of glacier mechanics, such as the appropriate relation between stress and strain at tremendous basal shear stresses, which are inconceivable in virtually all natural glacier settings. Despite an increasingly pressing need for a comprehensive understanding of how glaciers respond to highly transient forcings, however, most private sector glacier management projects cannot contribute meaningful observational data to advance such fundamental science due to proprietary considerations. Perhaps that can change in the future!

W. Colgan. 2014. Considering the ice excavation required to establish and maintain an open ice pit. Journal of Cold Regions Engineering. 28: 04014003. doi:10.1061/(ASCE)CR.1943-5495.0000067. Available here.

Supplementary online material (including animations): http://www.williamcolgan.net/som/CRENG113

cross_sectional_ice_velocity_open_ice_pit

Cross sectional ice velocities flowing into an open ice pit at excavation years 2.5 (left) and 10.0 (right) sampled from 30-year animations. Dashed black line denotes original ice surface, dash red line denotes ice pit wall. (from Colgan, 2014)

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Konwakiton Glacier triggers Mt. Shasta mudslide

Posted by William Colgan on September 23, 2014
Applied Glaciology / No Comments

This week Konwakiton Glacier was identified as the source of a mudslide that flowed down the side of Mt. Shasta, USA, for several hours. The US Incident Information System (InciWeb) states that “mudslides are more prevalent [at Mt. Shasta] during drought years due to increased solar exposure of the glaciers”. Recent and prolonged drought conditions in California this past summer have apparently left Mt. Shasta’s glaciers particularly exposed to solar radiation, resulting in more meltwater production than usual. InciWeb suggests that englacially or subglacially stored meltwater was released from Konwakiton Glacier by an unspecified disturbance event. While rain on ice events have triggered past mudslides, Mt. Shasta is a stratovolcano in a seismically active region. In any case, abrupt releases of glacially stored water are a very unique cryospheric hazard!

InciWeb report: http://inciweb.nwcg.gov/incident/4120/

Konwakiton_glacier_post_mudslide

Konwakiton Glacier on Mt. Shasta after the mudslide. (from InciWeb)

Mt_Shasta_mudslide

The Mt. Shasta mudslide crossed Pilgrim Creek Road and Forest Service Road 31. (from InciWeb)

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Proglacial Mines: Ice Flow and Infrastructure

Posted by William Colgan on September 15, 2014
Applied Glaciology, Glaciology History / No Comments

Last week Radio Free Europe released some photos of the Kumtor Gold Mine in Kyrgyzstan, where Centerra Gold Inc has been excavating approximately 10 MT of ice per year from the Lysii and Davidov Glaciers that flow into the open pit. In 2012 Mining.com reported that production estimates were down-revised due to a combination of “substantial acceleration of ice” and labor disruptions. These recent photos show infrastructure damage resulting from what appears to be glacier advance.

While no doubt curious, such a geotechnical management challenge would not be unique. In 1977, Eyles and Rogerson described how several positive mass balance years on the Berendon Glacier in Canada could cause sufficient terminus advance to threaten the adjacent Granduc Operating Company ore processing plant. In response, the Granduc Operating Company began discharging 30°C wastewater, year-round for five years, directly on to the glacier terminus to prevent advance. Glaciers are indeed dynamic landscape features for planning purposes!

Radio Free Europe photo series: http://www.rferl.org/content/qishloq-ovozi-kumtor-gold-mine-bad-shape/26555319.html

Eyles, N. and R. Rogerson. 1977. Artificially induced thermokarst in active glacier ice: An example from northwest British Columbia, Canada. Journal of Glaciology. 18: 437–444.

Kumtor_glacier_damage

Infrastructure damage resulting from what appears to be glacier advance at the Kumtor Mine in Kyrgyzstan (from Radio Free Europe: Kumtor Gold Mine Appears To Be In Bad Shape)

Granduc_glacier_thermokarst

Intentional thermokarst of the Berendon Glacier by the Granduc Operating Company. Red line denotes Summit Lake stream, which has been diverted upglacier at A. Hot waste water is added at B, and flow is subglacial until C. The stream exits the glacier terminus at D. (from Eyles and Rogerson, 1977)

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Brucejack Mine: Knipple Glacier Road

Posted by William Colgan on September 12, 2014
Applied Glaciology / No Comments

Full project environmental impact statement: http://www.ceaa-acee.gc.ca/050/details-eng.cfm?evaluation=80034

Brucejack_glacier_road

Brucejack Gold Mine access road over the Knipple Glacier (from the Brucejack Gold Mine Project Application for an Environmental Assessment Certificate Appendix 10-C).

Brucejack_glacier_road_overview

Overview map of the Brucejack Gold Mine access road over the Knipple Glacier (from the Brucejack Gold Mine Project Application for an Environmental Assessment Certificate Appendix 10-C).

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