Permafrost - Definition

Fossil pingo

Depressed area that is sometimes water filled and is formed because segregated ice in core of pingo has melted and ground has subsided

Rock glacier

Similar to an ice glacier but with more rock debris

Relief

Slope of permafrost can vary between north and south facing

Thermokarst

Uneven topography with depressions and small lakes caused by thawing of ice rich permafrost. Can produce features such as sink holes, thaw lakes, beaded streams and drunken forests

Talik

Unfrozen ground under permafrost

Ice wedges

V-shaped masses of vertically foliated ice. Cold winter ground contracts and cracks and then thawing of snow or train in the spring gets frozen in the cracks

Ground ice

All types of ice found underground

720m

Cameron Island has the thickest permafrost in Canada with

Sorted patterned ground

Flat areas, patterned ground occurs as polygons or circles b/c of the sorting of particles in soil or till

Frost heaving

Freezing of pore water causes an expansion of 9% and the surface will be heaved up slightly

Pingo ice

Freezing of water intruded under pressure. Largest and most spectacular permafrost feature

Peat plateaus

Frozen peat deposits occurring in unfrozen bogs

20, 50

Have that occurs due to the excess ice that forms during the growth of segregated ice can range from __ to __mm

Clay

Ice lenses do not form in grounds with low permeability such as

1, 5

Ice wedges may grow to as much as _m in width and _m in depth

Vegetation and snow

Insulation for permafrost

Active layer

Layer above permafrost table that thaws in the summer

1, 7

Palsas can rise _-_m above the surrounding land

Unsorted patterned ground

Patterns due to changes in vegetation, soil, cracks in the ground, or ice wedges below the surface

Permafrost

Perennially frozen ground having a temperature below 0 for at least two consecutive years

Palsa

Mounds of peat, often oval shaped. Contain segregated ice lenses

Patterned ground

Occurs in shapes such as nets, circle, or polygons

Differential heave of particles of various sizes

One of the ways that sorting occurs is by

60, 400

Pingo ice can range up to __m in height and ___m in diameter

Mini volcanoes

Pingo ice looks like

Permafrost table

Surface separating active layer and permafrost

Pore ice

The normal pore water that has frozen

Solifluction

When melting snow cause active layer to sag b/c of excess moisture

Ice lenses

When moisture, diffused within soil or rock, accumulates in a localized zone.

Excess water

When thawed ice lenses yield

Segregated ice

Where extra water has been drawn to the freezing front