sub-permafrost or intra-permafrost aquifers. Hydraulic (open-system) pingos result from groundwater flowing from an outside source, i.e. Hydraulic pingos ĭiagram showing how open system (hydraulic) pingos are formed. However, during summer months the ice core of the pingo begins to melt which causes the mound to cave in. This results in the formation of a mound due to the upwards pressure. In winter months this sediment begins to freeze which leads to expansion of sediment, confining the water and increasing the pressure. This indicates that the ground is insulated, allowing liquid water to collect underneath the sediment.
This type of closed system pingos is formed in an area where a lake has been infilled with sediment.
The figure above illustrates this process and the changes that occur throughout the year. The formation of these landforms occurs when layers of permafrost generate an upwards movement or pressure, resulting in masses of confined soil freezing, which pushes material upwards due to expansion. These pingos are found in flat, poorly drained areas with limited groundwater available such as shallow lakes and river deltas. They occur in regions of continuous permafrost where there is an impermeable ground layer. Diagram showing how closed system (hydrostatic) pingos are formedĬlosed systems, also known as hydrostatic pingos are formed as a result of hydrostatic pressure that has built up within the core of pingos due to water.
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