Geological Research Team2005-2006

Elizabeth City State University
Department of Geological Environmental and Marine Science

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Lloyd W. Mitchell, Ph.D., M.P.H., M.S., R.S.



Brian A. Campbell,



Sharain Halmon


Relationship of Ice Crack Morphology of the Southern Greenland

Ice Sheet to Iceberg Calving in the North Atlantic


In an effort to understand the influence of ice crack geomorphology on the on iceberg calving, 142 images of newly calved icebergs were analyzed using a newly developed crack classification system. Classification began by placing each iceberg's primary crack onto a classification grid containing eight categories. The eight categories were: Linear (being straight or slightly curved), Lightning (stair stepped at right angles), Arched (a slow definite curve), Multi-Arched (having one or more arched crack), Married (combining two or more of any category), Honeycomb (a field of uniformed shaped cracks), Jagged (sporadic, random resembling lightening with out straight angles) , and Other (any geometry that does not conform to the above categories). Additionally, all iceberg images were subjectively classified into one of these six categories; baby bergs (the size of a small vehicle) small berges (the size of a small house) medium bergs (the size of a large house or small building) large bergs (the size of a large building or skyscraper) and mega berges (greater than the size of a city or small state). We also chose to differentiate the icebergs studied from a shipping hazard standpoint, to this end Babybergs, as well as surface ice chunks, and ice floe chunks, were not included in this study. Additionally in preparation for this study researchers made preliminary contact with several organizations such as the International Ice Patrol, NASA, IPY and other organizations that are concerned with the tracking and monitoring of iceberg calving and migration. Results of data analysis showed: 100% (n=8/8) Mega bergs calved from linear cracks. 87.5% (n=14/16) large icebergs calved from linear cracks with the remaining 12.5% (n=2/16) calving from lightning cracks. Of the medium icebergs50% (n=32/64) calved from linear cracks with 15.63% (n=19/64) calving from lightning cracks and 12.5% (n=8/64) calving from married cracks. Of the small icebergs (n=54), which were the most difficult to visualize, 68% (n=37/54) showed calving from married with arch(es) or married with jagged or other cracks , 12.96% (7/54) calving form jagged cracks, 7.40% (4/54) calving from lightning cracks, with the remaining percentages calving from other crack types. The conclusion of this study indicates that linear cracks have been identified as the primary crack type for mega bergs as well as the majority of large bergs. The occurrence of a linear primary crack decreases with the size of the ice berg.

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