1. An introduction to where, how, and why glaciers form
Glacier Basics
An introduction to where, how, and why glaciers form

2. What is a glacier?
Large mass of moving ice that originated on land from accumulation, compaction, and recrystallization of snow
When snow is added to a glacier faster than ice and snow melt, the glacier gets larger
Largest fresh-water reservoir on Earth (75% of world’s fresh water)
Two main types
Continental glaciers /ice sheets
Alpine/valley glaciers

3. Continental Glaciers
Massive sheets of ice that may cover millions of square kilometers, that may be thousands of meters thick, and that are not confined by surrounding topography
Are also called ice sheets

4. Alpine Glacier
Narrow, wedge-shaped mass of ice that forms in a mountainous region that that is confined to a small area by surrounding topography

5. Where are glaciers found?
Glaciers are found on every continent except Australia
Found in polar regions and mountain ranges (and other planets)
Usually glaciers start at higher elevations and flow downward and outward
Hugo Ahlenius, UNEP/GRID-Arendal, overview of world glaciers and ice caps, UNEP/GRID-Arendal Maps and Graphics Library, (Accessed 22 June 2009)

6. Glacier formation
Glaciers form wherever more snow accumulates in the winter than melts in the summer.
Glaciers form above the snowline or lower limit of perennial snow in the zone of accumulation.
Glaciers move downhill in response to gravity
Glaciers melt or sublimate in the zone of wastage/ablation
Crevasses are large cracks which reach the glacier surface and form by a number of ways

7. Glacial Movement Glaciers move in 2 ways:
Basal Slip: simple response due to gravity whereby the ice moves downhill over bedrock and slipping over a thin layer of water.
Internal Plastic Flow: If you stack a LOT of ice, the pressure increases and the ice behaves plastically, meaning that the lower layers will start to deform. Flow in a glacier is smooth at depth, but in the top ~50 m ice is brittle and cracks

8. Glacial erosion Rate of glacial erosion depends on
Rate of glacial movement
Ice thickness
Underlying rock characteristics

9. Glacial erosion Plucking Abrasion
Deep depression in rock when moving glacier loosens and dislodges rock from bedrock at base or side of glacier
Sediment carried and deposited by glaciers is called glacial drift
Abrasion
Caused by glacial flow
Striations form

10. How do glaciers change a landscape?
Lateral moraines
Horn
Arête
Cirque
Grosser Aletschgletscher (Bernese Alps), Dirk Beyer
Main glacier
Medial moraines

11. How do glaciers change a landscape? Erosional Features
Horns
Arête
Cirque
Tarn lake
Hanging valley
How do glaciers change a landscape?
Erosional features
Truncated spur
Paternoster lakes
U-shaped valley
Erosional features of a glaciated valley, DK

12. Glacier anatomy: Alpine Glaciers
Hanging Valley: Form where a higher elevation glacier flows into a larger glacier that has a deeper canyon
Hanging valley
U-shaped valley
Yosemite Valley

13. Crevasses Form by: Two glaciers colliding
Accelerations in glacier speed
Changes in underlying topography

14. Glacial Erosion - Landforms
Cirque- Moving glacier pulls blocks of rock from the floor of the valley and create a bowl shaped depression

15. Glacial Erosion - Landforms
Arête- Sharp, jagged ridge forms between cirques

16. Glacial Erosion - Landforms
Horn- When several arêtes join, they form a sharp, pyramid-like peak

17. Glacial Erosion - Landforms
Fjord- forms where a glacier has eroded a valley into the sea. When glacier retreats, the sea fills in.

18. Glacial Deposition - Landforms
Erratic- Large boulders carried a long distance from their original location

19. Glacial Deposition - Landforms
Moraines- The debris that glacier grind up, carry, and push out in front of it

20. Glacial Deposition - Landforms
Drumlins- long, tear shaped mound

21. Glacial Deposition - Landforms
Braided Streams- multiple small, shallow channels

22. Glacial Deposition - Landforms
Kettles- occurring as the result of blocks of ice caving in