Lab 13:
Glacial Processes, Landforms and Indicators of Climate
Change
Objectives:
- Identifying mountain v. continental glaciers
- Glacial morphology
- Relation of specific features to glaciation type
- Identification of erosional and depositional features
- Water bodies of glacial regions
- Using glaciers as climate indicators
Introduction:
Glaciers: large ice masses on land, where winter accumulation exceeds summer ablation
Accumulation: compacted snowfall
Ablation (wastage): loss of snow and ice by melting and sublimation (change to gas)
Zone of accumulation: area where snowfall is collected, compacted and recrystallized under
it’s own weight
Zone of ablation: area of melting and sublimation of snow back to liquid and vapor forms
Snowline: boundary between the zones of accumulation and ablation
Terminus: the bottom end of the glacier, where it terminates
Motion down slope causes erosion (wearing away) and plucking of rock material
Pluck: freezing around rock material and breaking it free
Glacial Retreat: melting faster than accumulating, appears to retreat up the valley
Drift: rocky gravel, sand, silt and clay deposited by the glacier
Till: unstratified deposits directly from melting glacier
Types of Glaciers:
Figure 13.1
Cirque: small, semicircular to triangular glaciers that form on the sides of mountains
Valley: long glaciers that flow down stream valleys in mountains
Ice sheet: vast pancake shaped ice mount covering large portion of a continent, flow not
controlled by underlying topography
Glacial Processes and
Landforms:
Mountain glaciation - Figure 13.2
Characterized by cirque, valley and piedmont glaciers
Crevasses: cracks in the ice from varied flow velocities
Horns, tarns, cirque, arête, paternoster lakes, hanging valley
Continental
glaciation - Figure
13.7
Last record in US was the Pleistocene Ice Age, 10,000 yrs ago
Covered
Drumlins, marshes, kettle lakes, recessional and terminal moraine, esker
Distinguishing between the two: Figure 13.3, 13.4,
13.5