Defining periglacial landscapes

Periglacial landscapes form in extremely cold environments without a permanent covering of ice. These areas typically feature ice within the soil, which influences how the land develops over time.

Key features of periglacial environments

These landscapes experience harsh conditions that affect soil, water, and plant life. The temperature often stays below freezing for much of the year, creating a challenging setting for natural processes.

Main climatic characteristics:

• No permanent ice cover on the surface
• Average temperatures ranging from 1 °C to –15 °C, with frequent or constant freezing
• Low precipitation, usually 380 mm or less per year
• Distinct seasons, including brief mild summers and long cold winters

Soil and permafrost in periglacial areas

Soil in periglacial landscapes is generally thin and lacks nutrients. A key feature is permafrost, which is ground that remains frozen for two or more years.

Structure of permafrost layers

Above the permafrost is an active layer, which is the top layer of soil where ice melts during summer, allowing some thawing and refreezing.

Key aspects of permafrost formation:

• The active layer is relatively thin and thaws seasonally
• Permafrost extends deeper until geothermal heat prevents further freezing, sometimes reaching depths of as much as 1.5 km

Types of permafrost based on coverage

Permafrost varies in how much of the ground it covers, depending on local temperatures and conditions. This variation is classified by the percentage of frozen ground in an area.

Categories of permafrost:

• Continuous permafrost - Typically 90% or more of the ground is frozen, requiring mean annual temperatures below –5 °C
• Discontinuous permafrost - Between 50% and 90% of the ground is frozen, forming in fragmented patches where mean annual temperatures are below 0 °C for at least two years
• Sporadic permafrost - Between 10% and 50% of the ground is frozen, occurring in isolated patches influenced by specific microclimatic conditions
• Isolated permafrost - Less than 10% of the ground is frozen

Vegetation in periglacial environments

Plant life in periglacial areas is slow-growing and short. These landscapes are part of the tundra biome.

Adaptations and common plant types

Harsh climates limit plant development.

Typical vegetation features:

• Slow-growing and short plants
• Dominance of grasses, mosses, and lichens
• Occasional small, dwarf trees in sheltered spots

Global distribution of periglacial landscapes

Periglacial environments occur in specific locations where cold conditions persist.

Primary locations of periglacial areas

• High latitudes, such as areas near the Arctic Circle
• High altitudes, like plateaus in the Himalayas or around ice masses in mountain ranges
• Continental interiors at lower latitudes, where the lack of coastal warming from seas allows colder conditions to prevail

Historical changes in periglacial distribution

The extent of periglacial landscapes has varied over time.

Changes over time

• During the Last Glacial Maximum, periglacial areas extended as far south as the Mediterranean and northern Japan, covering approximately one-third of Earth's land surface
• Today, permafrost covers around 20% to 25% of the land surface, compared to 33% during the last Ice Age