Glaciated Landscapes: Periglacial Processes Flashcards
What is freeze-thaw?
Where there is regular temperature fluctuation, water flows into cracks and expands by nearly 10%, widening or splitting the crack.
What is frost-shattering?
Water within rocks freezes and expands by nearly 10%, shattering the rock. In periglacial areas scree develops as scree slopes due to frost shattering.
What periglacial process forms blockfield/felsenmeer?
Frost shattering
What is blockfield/felsenmeer?
Extensive spreads of angular boulders formed by frost shattering
What is nivation?
A combination of processes including freeze-thaw and possibly chemical weathering, that occurs under the snow which enlarges small hollows into nivation hollows, which is vital in the formation of a corrie
What is solifluction?
Downslope movement of the active layer on slopes as shallow as 2 degrees, caused by excessive lubrication when the active layer thaws in the summer
What are solifluction deposits in southern Britain known as?
Head
What is frost heave?
Ice crystals develop as the active layer refreezes, which pushes small rocks upwards due to their lower specific heat capacity, this then causes the soil surface to expand upwards into small domes. The small rocks then reach the surface, and roll into the depressions between the domed surfaces forming patterned ground
What is groundwater freezing?
In areas of thin or discontinuous permafrost, water seeps into the upper ground layers and freezes or is frozen from a small lake, which expands by nearly 10%, pushing the sediments above into a dome, which forms pingos
What is ground contraction?
The soil in the active layer refreezes, causing the soil to contract, which opens up cracks on the surface. Meltwater with sediments then flows into the cracks, re-freezing and expanding by nearly 10%, which widens the crack. Year after year these processes form ice wedges and ice-wedge polygons
What is hydraulic pressure?
The movement of water through a rock profile due to pressure
What is hydrostatic pressure?
The movement of water due to the attraction of water molecules to other water molecules
What landforms does frost-shattering form?
Blockfield/felsenmeer and scree slopes
What landform does nivation form?
Corries
What landforms does solifluction form?
Solifluction lobes and sheets, and deposits known as head
