Glacier Notes

Cryosphere All of the frozen areas on Earth's surface where water exists in its solid form sea ice ice shelves icebergs ice sheets glaciers lake ice river ice snow permafrost

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   Mass of ice formed by the recrystallization of snow under its own weight Compacted snow becomes “firn” More snow has to be added than melted in the previous year's worth of snowfall so that 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

Cirque A semicircular or amphitheater-shaped feature created as glaciers scour back into the mountain

Arete Steep-sided, sharp-edged bedrock ridge formed by 2 glaciers eroding away on opposite sides of the ridge

Horn A pyramid-shaped mountain peak created by several glaciers eroding away at different sides of the same mountain

Glacial Striations Lines etched in bedrock under glaciers as individual particles of rock embedded in the glacier scratch the bedrock

Horn Arete Cirque

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

Formation of 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.

Retreating Glacier End moraine

medial moraine lateral moraine

Esker Long ridge formed by sediment deposition in sub-glacial streams

Kettle Lakes Formed by melting ice chunks in glacial debris

Drumlin A long, narrow, smooth hill of unstratifited glacial till. Points in the direction of flow.

Erratics Large boulders left behind after glaciers retreat

Southernmost extent of continental glacier Continental Glaciation Landform Features Southernmost extent of continental glacier

Retreat of South Cascade Glacier, Washington