Photo Friday: Glacier Foliation

This week’s Photo Friday features a structure common to most glaciers. Foliation is layering in glacier ice that has distinctive crystal sizes and/or bubbles. Typically, foliation is caused by stress and deformation as a glacier grinds over uneven terrain, but it can also originate as a sedimentary feature.

Sherman Glacier near Cordova, Alaska. Folding, and subsequent melting of the glacier, revealed a nested stratigraphy of concentric folia (Source: USGS).

 

According to a 1977 study published in the journal Tectonophysics, foliation in glaciers depends on the climate of the glacier. Temperate glaciers, for example, are defined by three types of ice (classified according to texture). Most abundant is a coarse-grained, bubble-rich ice, comprising two-thirds of the total ice exposed at the glacier surface. About one fifth of glacier ice is of a slightly larger, coarse clear variety, while the remainder is fine-grained and bubble-rich. In colder glaciers, such finer-grained ice is most common.

Striking foliation on Fountain Glacier in Bylot Island, Canada (Source: Richard Waller/Twitter).

 

A cross-section at the terminus of Lamplugh Glacier, Alaska, exhibiting truncated folia (Source: USGS).

 

Foliation distinguishes glacier ice from snow on Canada’s Athabasca Glacier (Peter G Knight/Twitter).

 

 

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