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

?

?

?

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