BESIBERRIS GLACIGENIC ROCK GLACIER (CENTRAL PYRENEES, SPAIN): MAPPING SURFACE HORIZONTAL AND VERTICAL MOVEMENT (1993-2003)

A ten-year (1993-2003) geodetic survey was conducted at the Besiberris rock glacier a tongue-shaped, glacigenic rock glacier located in the eastern-central Spanish Pyrenees (42 degrees 35 '48 "N, 0049 '20 "E). Displacement measurements were made on three traverse lines across the rock glacier and mapped by geostatistical kriging interpolation methods. Surface horizontal velocity increases from the head to the toe sectors (average values: traverse line A = 8.72 cm yr(-1); line B = 10.65 cm yr(-1); line C = 13.35 cm yr(-1)). Velocities are greater at the axis of the rock glacier compared to its lateral margins. In terms of vertical movement, the rock glacier has shown clear thinning of an ice-core. In all three traverse lines, surface lowering has been detected (average values: line A = 5.00 cm yrn(-1); line B = 7.10 cm yr(-1); line C = 5.27 cm yr(-1)). This general lowering is interpreted as the adjustement of the rock glacier to the climatic amelioration (higher temperature, drier conditions and reduced snowfall) observed in the Pyrenean region since the end of the Little Ice Age and accentuated in the last few decades.