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

       Piedmont: mergers of two or more valley glaciers at the foot of a mountain range

       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 Alaska, Canada, and most of the northern continental US

               Drumlins, marshes, kettle lakes, recessional and terminal moraine, esker

       Distinguishing between the two: Figure 13.3, 13.4, 13.5