Glaciers and Glacial Landforms

Glaciers

large, long lasting masses of ice, formed on land, that move under their own weight (due to gravity)

Valley Glaciers

confined to valleys in mountainous areas

Alpine Glaciated Terrains

glacially-sculpted mountainous regions

Piedmont Glaciers

Valley glaciers that flow out onto broad flat areas

Ice Fields

multiple interconnected glaciers in high-altitude mountianous regions. (valley glaciers flow outward from ice field center)

Ice Sheets

Masses of ice covering large areas of land

Continental Glaciated Terrains

vast areas of continents formerly covered by glacial ice

Ice Caps

dome-shaped ice masses (like mini ice Sheets)

Crevasses

cracks that form in the rigid upper portion of glaciers in zones of tensional stress

Movement of an Ice Sheet

ice flows outward from a central point to lower elevations

Accumulation

snowfall and recrystallization to ice

Zone of accumulation

upper glacier

Ablation

loss of ice by melting, calving, evaporationZone

Zone of ablation

lower glacier

Equilibrium line

line that separates zones of accumulation and ablation

accumulation > ablation

positive budget

ablation > accumulation

negative budget

plucking

fragments of rock are frozen into the base of the glacier

Hanging Valley

less incised valley formed by glacial tributary

Cirque

half-bowl land form at head of valley glacier

horn

sharp peak surrounded by cirques

arete

sharp ridge that separates adjacent valleys

Sediment Load

rock fragments plucked up by ice, rockfall onto glacier surface

Till

unsorted (= wide range of grain sizes), unlayered, often angular sediment deposited directly by glacial ice (when it melts)

Moraine

a body of a till

Ground Moraine

thin blanket of till deposited as ice melts during progressive recession

End (recessional) moraine

till deposited in a pile during a pause in recession

Drumlin

streamlined hill of till

Outwash

sediment deposited by glacial melt water. layered and moderately well-sorted. forms broad, flat outwash plains.

Esker

long, sinuous ridge of water-deposited sediment. depositedd in tunnels under melting ice sheets

Kettle

depression left when block of ice is surrounded and buried by outwash, then ice block melts

Glacial Lake

form in erosional depressions or by damming water with ice or glacial deposits