Compression overlapping of floating ice cover in alternating overthrusts and underthrusts
Aerial photograph showing two thin ice sheets (made of nilas) that are moving toward each other. Along the length of the contact between the two sheets, segments where one sheet climbs onto the other alternate with others where it is the other way around. The lighter areas are where the ice thickness has doubled due to the overlapping process. This pattern is known as finger rafting. In many cases, it is highly systematic.Finger rafting in the Weddell Sea, Operation IceBridge photo, 2017.Idealized three-dimensional representation of finger rafting, It occurs when two thin ice sheets converge toward each other.Finger rafting derives its name from its resemblance to the interlocking of fingers. Note that the fingers shown here are not interlaced normally (with all ten fingers showing from the top), but interlaced as in finger rafting (with only five fingers visible from either the top or bottom). [note 1]Rafted ice observed during MOSAiC Expedition in June 2020.
Finger rafting develops in an ice cover as a result of a compression regime established within the plane of the ice. As two expanses of sea ice converge toward another, one of them slides smoothly on top of the other (it is overthrusted) along a given distance, resulting in a local increase in ice thickness. The term finger rafting refers to the systematic alternation of interlocking overthrusts and underthrusts involved in this process.[1][2][3] Such a pattern derives its name from its resemblance to the interlocking of fingers.[note 1]
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