Key terms and definitions

With my previous topic of glaciers, I created a table of key words and definitions and I feel that this really helped me to get to grips with the subject as it helped to know what key words to look out for! I am therefore going to do the same with periglacial environments.

Active layer	The uppermost ground layer which thaws in the summer and freezes in the winter
Alpine permafrost	Found at much higher elevations
Continuous permafrost	Underlies nearly all of the landscape (except maybe rivers and deep lakes which don’t freeze through to the bottom)
Discontinuous permafrost	Zones of permafrost which have numerous scattered thawed areas
Freeze-thaw weathering	Water enters cracks or joints in rocks. When temperatures drop it then freezes, causing the water to expand which puts pressure on the rock. When temperatures rise the water contracts. This repeated process causes the rock to weaken and eventually shatter into many angular pieces
Frost creep	Slow, downslope movement of materials because of frost heaving and thawing and is influence by gravity
Frost heave	The upward or outward movement of the ground surface which occurs as a result of formation of ice in the soil
Gelifluction	Slow, downslope flow of unfrozen materials on frozen ground (permafrost). Form of solifluction
Ground Ice	All types of ice that is contained both in freezing and frozen ground
Ice lenses	Horizontal layers of segregated ice
Ice Wedge	Downward, narrowing ice masses. Can be between 2 and 3 metres wide at their base and can extend into the ground up to 10 metres
Needle Ice	Groups of narrow slivers of ice that form in more moist soils when temperatures drop below freezing at night
Palsas	Low mounds of permafrost with cores of segregated ice and peat
Patterned ground	Distinct, symmetrical geometric shapes which are formed by ground material
Permafrost	Frozen ground that stays at or below 0°C for two or more years
Pingos	Mounds of earth covered ice
Pore Ice	Ice that develops in the pores of soil and rocks where water can accumulate and then freeze
Sand Wedge	In more arid, cold environments, ice wedges may accumulate sand blown in by the wind within winter cracks.
Segregated Ice	Masses of almost pure ice that grow within permafrost
Solifluction	The slow, downslope flow of sediment and soil which is saturated with water
Sporadic permafrost	Small scattered areas of permafrost found in generally unfrozen areas
Talik	Permanently unfrozen ground in regions of permafrost
Talik (closed)	Unfrozen ground that is encased within permafrost
Talik (open)	Unfrozen ground that is open to the surface
Talik (through)	Unfrozen ground that is exposed to the ground surface as well as to a larger mass of unfrozen ground beneath it

As with the glacier definition table, it would be good to give students this at the start of the topic so that they have it for reference. At the end, as a fun sort of test they could cut the tables up into key terms and definitions and have to match them together. When learning these terms it would be good to show the students pictures as it is good for the students to be able to apply what they are learning to real life landscapes.