glacial grooves

grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial striations.
Striated Graywackie, Yale Glacier, Alaska. 1997. Parallel striations and bedrock fracture trends (across the left side of the image) are clearly visible in this photo. (Photo courtesy of Tom Lowell, University of Cincinnati.)

glacial erratic

a boulder swept from its place of origin by glacier advance or retreat and deposited elsewhere as the glacier melted; after glacial melt, the boulder might be stranded in a field or forest where no other rocks of its type or size exist.
Erratic boulder, northeastern Manitoba, Canada. A sense of the size of the glacial erratic can be estimated by noting the person standing in front of the boulder, on the left side. This erratic, as well as neighboring ones, were carried by the Keewatian Ice Sheet. (Photo courtesy of Lynda Dredge,...

glacial advance

when a mountain glacier's terminus extends farther downvalley than before; occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.


fountain that develops when water from a conduit is forced up to the surface of a glacier; also called a negative mill.

free water

free water is that portion of the pore water that is free to move between interconnected pores under the influence of gravity.
Free water at the base of Dirt Glacier, British Columbia, in 1904. (Photo courtesy of C.W. Wright. Archived at the World Data Center for Glaciology, Boulder, CO.)

forel stripes

shallow, parallel grooves on the face of a large melting ice crystal.

forbes bands

alternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter.


layering in glacier ice that has distinctive crystal sizes and/or bubbles; foliation is usually caused by stress and deformation that a glacier experiences as it flows over complex terrain, but can also originate as a sedimentary feature.

flow finger

a small percolation channel that is a beginning path for surface meltwater through snow or firn.


glacial troughs that fill with sea water.


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