1 / 22

Glacier Basics

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

deacon-wong
Télécharger la présentation

Glacier Basics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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. 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 Glacier formation

  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 • 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? Lateralmoraines Cirque Horn Arête Grosser Aletschgletscher (Bernese Alps), Dirk Beyer Mainglacier Medialmoraines

  11. How do glaciers change a landscape?Erosional Features Horns Arête Cirque Tarnlake Hangingvalley Truncated spur Paternoster lakes U-shaped valley Erosional features of a glaciated valley, DK www.wiredantarctica.com

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

  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

More Related