Glaciers
Glaciers form when SNOW remains for more than one year, compacts and recrystallizes
in to glacial ice
Glaciers form in polar environments due to very cold temps (little to no melting) with
small amounts of snowfall each year
Glaciers form in temperate climates due to very large amounts of snow (up to 100’ in the
Cascade Mts. of Washington) despite a large amount of melting in the summer months.
Glaciers form at all latitudes: near sea level in polar latitudes, at high elevations in the
tropics (Lewis Glacier on Mt. Kenya, glaciers on Mt. Kilimanjaro)
Glaciers grow above the permanent snow line (zone of accumulation) and decrease in
size below the snow line (zone of ablation).
Glaciers move by basal slip and internal deformation
Crevasses only form in the upper parts of glaciers due to brittle deformation of the ice.
Glacial ice is mainly water, with only small trapped air pockets left in the ice.
Glaciers ADVANCE if the climate cools or it becomes wetter
Glaciers RETREAT if the climate warms or becomes drier
Glacial EROSION
“U” shaped valleys
Hanging Valleys
Fjords
Glacial striations and polish
Aretes
Horns
Glacial DEPOSITION
TILL-characteristics relative to stream deposits
Moraines-terminal, lateral, media-indicators of extent of glacial ice
Continental ice sheets and ice ages
8-10 ice ages over the past 1 million years
Isostatic (Glacial) rebound-changes in land height due to weight of ice on the land and
the lag time between ice growth/melting and ground deformation.