periglacial landforms and landscapes Flashcards
what are the 7 different types of peroglacial landforms
-patterned ground
-ice wedges
-pingos
-terracetes
-solifluction lobes
-blockfields
-thermokarst
what process is key im the formation of patterned ground
outline how patterned ground is formed
-what are the 2 different shapes that patterned ground can be, what makes the 2 different
how long does this landform last
-frost heave of sotnes is key in the formation of patterned ground, it occurs underneath the active layer
-ice lenses exist within permafrost and they grow through repreated freezing and thawing, capillary action brings more water to the lens, causing it to grow further.
-when the ice lens expands, stones around the ice lense are shunted upwards
-larger stones roll down due to their weight
-fine sediments fill the space to stop larger rocks
polygons apear on flat surfaces
-they can either be polygons or stripes on steeper onclines where rocks roll downhill
-this landform lasts a medium amount of time as they can be disrupted by theh warmer periglacial conditions
what process is key in the formation of ice wedges
outline the formation of ice wedges
how long to ice wedges last
-frost action
-water infiltrates cracks in the permafrost and expands on freezing (frost action)
-water the filld the expanded ground.
-the process then repeats and leaves a large ice wedge
-ice wedges last a medium amount of time as temperatures must be consistently cold enough for the ice wedge to grow
how are both types of pingos typically formed
how is a open pingo formed
what type of permafrost does this occur on
how is a closed pingo formed
what type of permafrost is this produced on
how long do pingos last
-ground is forced upward through frost heave of an ice lens, leaving a mound.
open:
-water moves through unfrozen ground between areas of permafrost
-due to capillary action, the water groups together
-water freezes and creates an ice lens
-the ice lens continues to grow and pushes the unfrozen ground upwards
-occurs within discontinuous permafrost
closed:
-under a lake, permafrost is insulated and melts
-the lake will eventually dry up or freeze, leaving the unfrozen ground
-an ice lens will develop through capillary action when temperatures drop and water comes together
-when temperatures drop, permafrost advances and frost heaves the unfrozen ground upwards, creating a mound
-produced in continuous permafrost
-pingos last a medium amount of time as cracks in the ground allow water to seep in and melt the ice lens, warmer temps also melt the ice lens
what is the main process involved in the formation of terracetes
what is special about terracetes, (theory)
what is the most common theory explaining how terracetes are formed
how long do they last
-frost heave
-the formation of terractees is not wholly, known r agreed upon in geographical study, there are a few different theories
-the most common theory involves the intervetion of veegetation
-frost heave pushes particles of soil upwards, which would usually fall downhill through the process of creep
-however veegtation blocks the soil from falling, meaning it stays behind in a step shape, forming terraces
-terraceets last a sort-medium amount of time as thawing of the soil would disrupt the process of frost heave
outline the process of solifluction lobes
how long do they last
-they occur when the active layer thaws and solifluction occurs, tongue shaped lobes of soil fall down a slope due to gravity.
-solifluction lobes last a shrt-medium amount of time, as the soil cannot retain the strecthed structure for long and when temperatures rise the soil moisture content decreases
what are blockfields
how long do they last
-blockfields are rock-strewsn landscapes caused by extensive frost action of the landscape
-they last a medium-long amount of time as loose rocks can be displaced through weathering
what is thermokarst
how are they formed
how long do they last
-thermokarst refers to marshy,boggy wetlands caused when permafrost melts.
-they are formed through permafrost melting. any ice lenses within the ground originally, or landform such as pingos would melt and collapse. this can leaves holes in the ground which can also fill with meltwater
-they last a short-medium amount of time as they will dry up when temperatures rise and permafrost retreats
what is an ice lense
-a layer of ice that forms within soil when water moves to a freezing front and freezes, causing frost heave.
-this is common in periglacial environments
