Definition of a glacier:

Consider Glaciers and the hydrologic cycle.

Glacial budgets: When do glaciers form?

How do glaciers form? Pretty snowflakes are transformed into solid ice by a process that amounts to an icy form of burial metamorphism - They recrystallize due to confining pressure. The process:

Ice mechanics: The ice crystals that people interact with typically are brittle. When confining pressure is great, however, they deform ductilely, like rocks in the asthenosphere. The weight of 40 m. of overlying ice is usually enough to cause ice to deform ductilely. As a result, accumulations of ice thicker than this tend to flow downhill under their own weight. (Not surprising that Wegener got some of his ideas by watching the behavior of glacial ice.)

Mechanisms of glacial movement:


Glacial budgets: Glacial ice recedes or accumulates depending on the balance of accumulation and ablation - i.e. loss through melting, sublimation, and breaking off of icebergs.

Big concept: Landmarks like the firn limit or the toe of the glacier may move uphill or downhill depending on the glacier's budget, but any given parcel of ice always moves downslope.

Major types of glaciers are function of scale and geometry: Two are recognized: continental and valley.

Valley glacier profile:

Idiosyncrasies of glacial flow:

Processes of Glacial erosion:

Erosional features:

Erosional land forms that form from valley glaciers: These are what we think of as the typical features of regions like the Alps and high mountains of western North America. they may be occupied by active glaciers or may be left over when the glacier melts.

Glacial sedimentation:



Key concepts and vocabulary: