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Dynamic, evolution and structure of Pyrenean rock glaciers

Abstract:

The paper analyzes the fourteen rock glaciers inventoried in the Pyrenees. The genesis, surface morphology, internal structure, surface dynamics and morphostratigraphical characters are analysed according to studies made on different rock glaciers. The Pyrenean rock glaciers are included in two genetic typologies as talus rock glacier with periglacial origin, and debris-glacier rock glacier, of glaciogenetic origin. Both types are related to different surface shapes and internal structures. The internal structure shows a great diversity, with different structures for each of the four rock glaciers studied. Rock glaciers show a wide range of horizontal displacements, although the displacements are moderate in all cases, except the Argualas rock glacier, with displacements similar to the most frequents alpine ones. In all cases rock glaciers show a trend toward thinning. The study of horizontal and vertical displacement has permitted us to establish two different dynamic models: "pushing rock glaciers", the most dynamic ones, and "attenuated rock glaciers", characterized by the melt processes at the frontal area. Finally, the rock glaciers are linked to two chronological periods, those generated during the Holocene, and those developed during the Little Ice Age. Pyrenean rock glaciers are located in marginal environments where the topoclimate conditions are favourable to rock glaciers develop and conservation. The rock glaciers are very good geoindicators of permafrost and changes related to cold environments in the high mountain of the Pyrenees. © Universidad de La Rioja.