I. Glaciers: a part of two basic cycles in the Earth system

       A. Glaciers are a part of both the hydrologic cycle and rock cycle

       B. Glacier - a thick mass of ice that forms over land from the compaction and recrystallization

            of snow and shows evidence of past or present flow

       C. Types of glaciers

             1. Valley, or alpine glaciers – form in mountainous areas

             2. Ice sheets, or continental

       D. Movement of glacial ice

             1. Types of glacial movements

                  a. Plastic flow

                  b. Slipping along the ground

             2. Zone of fracture

                  a. Uppermost 50 meters

                  b. Crevasses form in brittle ice

             3. Zone of accumulation – the area where a glacier forms

             4. Zone of wastage – the area where there is a net loss due to melting

       E. Glaciers erode by

             1. Plucking – lifting of rock blocks

             2. Abrasion

                  a. Rock flour (pulverized rock)

                  b. Striations (grooves in the bedrock)

        F. Landforms created by glacial erosion

             1. Glacial trough

             2. Hanging valley

             3. Cirque

             4. Arte

             5. Horn

             6. Fiord

       G. Glacial deposits

             1. Glacial drift

                  a. All sediments of glacial origin

                  b. Types of glacial drift

                      1. Till

                           a. Material that is deposited

                             directly by the ice

                           b. Glacial erratics (boulders embedded in till)

                      2. Stratified drift

                           a. Deposited by meltwater

                           b. Sediment is sorted

             2. Depositional features

                  a. Moraines

                      1. Layers or ridges of till

                      2. Types

                           a. Lateral

                           b. Medial

                           c. End

                                1. Terminal end moraine

                                2. Recessional end moraine

                           d. Ground

                  b. Outwash plain, or valley train

                  c. Kettles

                  d. Drumlins

                  e. Eskers

                  f. Kames

 

H. Glaciers of the past-the earth has experienced at least 5 major glacial periods.  The last of these ended about 10,000 years ago.  Many erosion and depositional features remain today from that extensive glaciations.

              

  I. Causes of glaciation-the successful theory of glaciation must account for the onset of glaciation, the alternation of glacial and non-glacial periods, and the end of glaciation.  The theory of place tectonics is one explanation, and orbital parameters is the other.

              

 

  II. Deserts

       A. Geologic processes in arid climates

             1. Weathering-Not as effective as in humid regions

                  

             2. Role of water in arid climates

                  a. Streams are dry most of the time

                  b. Desert streams are said to be ephemeral (Flow only during periods of rainfall)                    

                  c. Desert rainfall

                      1. Rain often occurs as heavy showers

                      2. Causes flash floods

                  d. Poorly integrated drainage

                  e. Most erosional work in a desert is done by running water

         

B. Basin and range: the evolution of a desert landscape

             1. Uplifted crustal blocks

             2. Interior drainage into basins produces

                  a. Alluvial fans and bajadas

                  b. Playas and playa lakes

             3. Erosion of mountain mass causes local relief to continually diminish

             4. Eventually mountains are reduced to a few large bedrock knobs called inselbergs

                 projecting above a sediment filled basin

         

C. Wind erosion

             1. By deflation (Lifting of loose material)

                  a. Produces

                      1. Blowouts

                      2. Desert pavement

             2. By abrasion

         

D. Types of wind deposits

             1. Loess - Deposits of windblown silt    

             2. Sand dunes

                  a. Mounds and ridges of sand formed from the wind's bed  load

                  b. Characteristic features

                      1. Slip face – the leeward slope of the dune

                      2. Cross beds – sloping layers of sand in the dune

                  c. Types of sand dunes

                      1. Barchan dunes

                      2. Transverse dunes

                      3. Longitudinal dunes

                      4. Parabolic dunes

                      5. Star dunes