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| Question | Answer |
| Areas of continuous permafrost | The northernmost: latitude of 60'+ North. Largely above the arctic circle. Greenland has the largest area of continuous permafrost, and Nova Zemlya is an example of an island under continuous permafrost - it is surrounded by unnavigable pack ice. Reaches as far south as Great Bear Lake in Canada. |
| Areas of discontinuous permafrost | Latitude of 50-60'N, underlying the majority of Canada and central Russia. Around the are of the Central Siberian Plateau. Surrounds Hudson Bay in Canada and reaches as far north as Great Bear Lake and the Great Slave Lake. |
| Sporadic permafrost | Largely found below 50' North. In North America it reaches as far north as Lake Winnipeg and drops down in a tongue around the area of the Rocky Mountains. In Siberia it is a wide strip, partially in the northern area of the Gobi Desert, at roughly 40'N. Underlies northern parts of Norway and Iceland and the southern tip of Greenland. |
| Ground ice | Water flows through the ground material into an ice lens which grows, disturbing the surface above it. Can include masses of surface ice that have been buried and insulated by fluvial sediments or landslides. |
| Ice wedges | Formed from meltwater running into a contraction crack which freezes in the autumn. Thaws in the spring, so the process is repeated, causing the crack to widen and deepen, becoming a tapered 'cone'. Occurs in areas with defined seasonal patterns of freezing and thawing. As the wedge gradually grows, it puts pressure on surrounding materials, displacing them. |
| Closed pingo | Formed in areas of continuous permafrost, from a lake which contains talik draining, causing the the recently exposed sediments or shallow water to cool. Permafrost develops and ice accumulates due to high lateral hydrostatic pressure, causing the surface to dome. They usually form in groups. |
| Open pingo | Smaller than a closed pingo, found in valleys or at the base of slopes in discontinuous permafrost areas. Water is inserted from beneath the permafrost and there is a lower volume of water, which is why it is smaller. |
| Death of a pingo | If a pingo grows to be too big, the surface cracks and the insulation is lost. The ice then thaws from the surface downwards and the entire structure can collapse. |
| Palsas | They form in wetland areas of discontinuous permafrost. Made of ice lenses, the interior is protected by the dry peat that forms the covering. When this cracks, the interior ice will melt and it will eventually collapse. There is no fluvioglacial material in a palsa. |
| Patterned ground | Material of different grain sizes and differential freezing of it within the active layer. The ground freezes downwards and moisture left in the active layer freezes, so when ice crystals form it expands, and the material above domes upwards. Where there are larger stones, the ground freezes more quickly - they have a lower heat capacity. The larger stones are pushed upwards and the patterns that develop are exaggerated by seasonal freezing and thawing over time. |
| Nivation hollows | Form on down wind slopes on valleys/mountains. Snow accumulates in the hollow and particles are loosened through intense cold and freeze-thaw weathering. Removed by meltwater in spring which leaves the rock exposed to be eroded again by the same method, causing further erosion of the hollow. |
| Solifluction | Dependent upon seasonality, meltwater is unable to percolate due to the permafrost that is beneath the active layer. The soil becomes saturated and can turn gentle slopes into steep ones, leaving terraces on the sides of valleys. |
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