Keywords

Any soil, subsoil, or other surficial deposit, or even bedrock, occurring in arctic, subartic, and alpine regions at a variable depth beneath the Earth's surface in which a temperature below freezing has existed continuously for a long time (from two years to tens of thousands of years). This definition is based exclusively on temperature and disregards the texture, degree of compaction, water content and lithologic character of the material.  The thickness of permafrost ranges from over 1000 m in the north to 30 cm in the south of the northern permafrost region; it underlies about one-fifth of the world's land area.

Geological keywords, such as “granite”, “lake”.  The definitions are generally taken from the AGI Glossary of Geology.  Keywords with a geographic context (e.g. Cape Smith Fold Belt, Selwyn Basin, Grenville Province) are assigned to a separate category.