Rock glacier

Rock glaciers are landform made up of stone debris and eventually ice which, due to their shape and profile, resemble glaciers (hence their name "rock glacier"). They have a lobed or elongated shape (tongue shape) characterized by well-defined margins with very steep sides and fronts. Rock glaciers have a surface rich in flow structures (wrinkles and furrows) which indicates the directions of movement and the deformations they undergo inside them, due to the presence of ice. This ice can be found in the form of ice lenses covered by debris as well as interstitial ice that fills the spaces of the matrix consisting of the rock blocks and smaller sized debris.

Precisely due to the presence of ice inside them they represent indirect evidence of the presence of permafrost. This term indicates the portion of land (rock, soil, debris) that is permanently frozen, i.e. has temperatures below 0 ° C for at least two consecutive years and therefore does not undergo thaw during the summer season.

Depending on their dynamic, rock glaciers are divided into active, inactive and wrecks. Active rock glaciers show downstream movements of the order of cm/year. Inactive rock glaciers still contain ice, but they do not show evidences of movement, for example due to counter-slopes of the bedrock on which they are located. Due to the difficulty of distinguishing between active and inactive forms, these two classes are often considered together, so rock glaciers that still contain ice are defined as intact. The relict forms, on the other hand, no longer contain ice and for this reason they are often difficult to identify.

The information layer of the regional Glacier Inventory Geoportal dedicated to rock glaciers contains information relating to these characteristic landforms of the periglacial environment and above all of the environment in which permafrost is present.

The work was carried out within the project "PermaNET - Long-term monitoring network of permafrost" (OP Transnational European territorial cooperation Objective 3 2007/2013 Alpine Space) , by the Direzione dell’Ambiente, del Terriotorio e della Mobilità sostenibile of Aosta Valley region in collaboration with other partners. Fondazione Montagna sicura - Montagne Sûre and ARPA VdA worked on the Inventory on behalf of the Direzione dell’Ambiente.

The work was made mainly by photointerpretation, starting from the crossing of the visual information of the orthophotos, of elaborations carried out starting from the digital model of the terrain (hillshade effect) and of infrared images, where available.

CONSULTATION OF THE CARTOGRAPHIC GEOPORTAL

Within the Inventory, each rock glacier is identified on the map by a brown polygon (on a small scale) and by its perimeter, each of them is associated with a form that summarizes the main characteristics.

Together with a unique numerical identification code, the name and the Municipality in which it is located, are also reported the morphometric data (minimum elevation of the front, average exposure, length, average width and surface) and some typical characteristics of rock glaciers: the geometry and the degree of activity.

The information published on the Inventory is only a part of that collected in the database relating to rock glaciers; in particular, it concerns information for which there is a greater degree of reliability.