a rocky crag or small mountain projecting from and surrounded by a glacier or ice sheet.

niche glacier

very small glacier that occupies gullies and hollows on north-facing slopes (northern hemisphere); may develop into cirque glacier if conditions are favorable.

negative mill

a geyser; a fountain that develops when water from a conduit is forced up to the surface of a glacier.

mountain glacier

a glacier that is confined by surrounding mountain terrain; also called an alpine glacier.
Muddy River Glacier carves its way through forested mountains near Frederick Sound in southeast Alaska. Typical of mountain glaciers, it is constrained on all sides by mountainous terrain. (Photo courtesy of the U. S. Navy, archived at the World Data Center for Glaciology, Boulder, CO.)


a nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses; also called a pothole.

moraine shoal

glacial moraine that has formed a shallow place in water.


a mound, ridge, or other distinct accumulation of glacial till.
Lateral and terminal moraines of a valley glacier, Bylot Island, Canada. The glacier formed a massive sharp-crested lateral moraine at the maximum of its expansion during the Little Ice Age. The more rounded terminal moraine at the front consists of medial moraines that were created by the...

meltwater conduit

a channel within, underneath, on top of, or near the side of a glacier that drains meltwater out of the glacier; usually kept open by the frictional heating of flowing water that melts the ice walls of the conduit.

medial moraine

a ridge-shaped moraine in the middle of a glacier originating from a rock outcrop, nunatak, or the converging lateral moraines of two or more ice streams.

mass balance

the difference between accumulation and ablation on a glacier; usually calculated on an annual basis.


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