GlacierNotes
Cryosphere
– sea ice– ice shelves– icebergs– ice sheets– glaciers
– lake ice– river ice– snow–permafrost
All of the frozen areas on Earth's surface where water exists in its solid form
Glacial Overview
• What are they?• How do the form?• How do they move?• What kinds of features do they form?
Glaciers
Mass of ice formed by the recrystallization of snow under
its own weight
Compacted snow becomes “firn”
More snow has to be addedthan melted in the previous year's worth of snowfall sothat it can accumulate in layers
Types of Glaciers
1. Ice sheets (continental glaciers) -- cover large areas of land
2. Valley (alpine) glaciers -- form at mountain tops and flow down valleys
Glacier: a Flowing River of Ice
• Mountain (Alpine)• Continental (Ice Sheets)
How Glaciers Move
Glacial Zones
Zone of Accumulation• Snowfall exceeds ablation–Ablation – reduction in glacial ice by
sublimation, melting, or calving
Zone of Melting (Ablation) (Wastage)• Ablation exceeds snowfall
Anatomy of a Glacier
Erosional Features
U-Shaped Valley / Fjord / Trough
Hanging Glacier
CirqueA semicircular or amphitheater-shaped feature created as glaciers scour back into the mountain
AreteSteep-sided, sharp-edged bedrock ridge formed by 2 glaciers eroding away on opposite sides of the ridge
A pyramid-shaped mountain peak created by several glaciers eroding away at different sides of the same mountain
Horn
Glacial StriationsLines etched in bedrock under glaciers as individual particles of rock embedded in the glacier scratch the bedrock
Cirque
Arete
Horn
The Matterhorn
In the Swiss alps
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Glacial Deposits
• Glacial deposit is called till.– Glaciers pick up everything in their path, even
the largest boulders.– Large amounts of sediment can be carried long
distances by glaciers.
Depositional Features
Moraines
• A mound or ridge of till deposited by a glacier
• The different places along a glacier’s advance will result in the different types of moraines– Lateral (Sides)–Medial (Middle)–Terminal (End)
Lateral Moraine
Unconsolidated material deposited along the sides of an alpine glacier
Medial Moraine
When two alpine glaciers flow together, their lateral moraines join, forming a medial (middle) moraine
Terminal/End Moraine
• The terminus of a glacier may remain stationary for years.• The sediment piles up in a ridge called an end moraine.• If this marks the furthest extent of the glacier it is a
terminal moraine.
Formation of end moraine
Retreating Glacier
End moraine
lateral moraine
medial moraine
Esker
Long ridge formed by sediment deposition in sub-glacial streams
Kettle LakesFormed by melting ice chunks in glacial debris
DrumlinA long, narrow, smooth hill of unstratifited glacial till. Points in the direction of flow.
Erratics
Large boulders left behind after glaciers retreat
Continental Glaciation Landform Features
Southernmost extent of continental glacier
Retreat of South Cascade Glacier, Washington