Periglacial Landforms Flashcards
What is a pingo?
A mound of earth covered ice.
How does a closed system pingo form?
A frozen lake with sediment on its floor insulates the ground beneath it, forming talik. When permafrost advances, unfrozen water at the bottom of the lake freezes and expands, pushing the sediment upwards and breaking up the lake, creating a mound.
What is talik?
Unfrozen ground
How does an open system pingo form?
In area of discontinuous permafrost, groundwater is forced up between areas of permafrost by hydraulic pressure. When it reaches the surface, it freezes, forcing the ground upwards.
How does a ruptured pingo form?
When the surface of a pingo is ruptured, the core melts and the pingo collapses.
Hw do ice wedges form?
Cold temperatures in winter form a crack which is about a metre deep and a few mm wide. In the summer, water flows into the crack, and freezes on contact with the permafrost. The cycle repeats, year after year, and the crack widens as the ice wedge forms.
What process leads to the formation of patterned ground?
Frost heave
What are the two types of patterned ground, and ta what angle do they form?
Stone polygons 6*
What is frost heave?
This process results from the formation of ice crystals and lenses in the soil. Fine grained soils expand unevenly upwards to create small domes. Small amounts of moisture in the soil below the stones freezes and turns to ice. By repeatedly freezing and thawing over time, these crystals and lenses heave stones upwards in the soil profile. In regions where temperatures vary between 0 and -4*C, frost heaving and thawing can sort material to form patterned ground. Larger stones move down the very low slopes due to their weight.
