Passer au contenu principal

Paleoclimatology (thesaurus)

Choisissez le vocabulaire dans lequel chercher

aligner
annoter
télécharger

Concept information

... > constituent of the planet Earth > earth surface > continental surface > soil > frozen ground > permafrost > pingo

Terme préférentiel

pingo  

Définition

  • Pingos are intrapermafrost ice-cored hills, 3–70 m (10–230 ft) high and 30–1,000 m (98–3,281 ft) in diameter. They are typically conical in shape and grow and persist only in permafrost environments, such as the Arctic and subarctic. A pingo is a periglacial landform, which is defined as a non-glacial landform or process linked to colder climates. It is estimated that there are more than 11,000 pingos on Earth. The Tuktoyaktuk peninsula area has the greatest concentration of pingos in the world with a total of 1,350 pingos. There is currently remarkably limited data on pingos. Pingos can only form in a permafrost environment. Evidence of collapsed pingos in an area suggests that there was once permafrost. Pingos can collapse due to the melting of the supporting ice and give rise to a depression in the landscape showing an inverse shape (horizontal mirror). There are two types of pingos (hydrostatic or hydraulic). The hydrostatic pingos are closed systems, they are formed as a result of hydrostatic pressure that has built up within the core of pingos due to water. They occur in regions of continuous permafrost where there is an impermeable ground layer. These pingos are found in flat, poorly drained areas with limited groundwater available such as shallow lakes and river deltas. 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. The hydraulic pingos are (open-system) pingos result from groundwater flowing from an outside source, i.e. sub-permafrost or intra-permafrost aquifers. Hydrostatic pressure initializes the formation of the ice core as water is pushed up and subsequently freezes. Open-system pingos have no limitations to the amount of water available unless the aquifers freeze. They often occur at the base of slopes and are commonly known as Greenland type. The groundwater is put under artesian pressure and forces the ground up as it makes an expanding ice core. It is not the artesian pressure itself that forces the ground up, but rather the ice core that is being fed the water from the aquifer. These are often formed in a thin, discontinuous permafrost. These conditions allow an ice core to form, but also provide it with a supply of artesian ground water. If water pressure entering an artesian pingo is strong enough, it can lift the pingo up allowing a sub-pingo water lens to form underneath. However, if the water lens starts to leak water it can cause subsidence which can compromise the structure. These pingos are often oval or oblong shaped. It is still not entirely understood why open system or hydraulic pingos normally occur in unglaciated terrain. (Adapted from: https://en.wikipedia.org/wiki/Pingo)

Concept générique

Traductions

URI

http://data.loterre.fr/ark:/67375/QX8-HTQ06D4F-1

Télécharger ce concept :

RDF/XML TURTLE JSON-LD