Active layer and borehole temperatures from La Foppa rock glaciers, Val Vallaccia, Central Italian Alps
The La Foppa site is a glacial cirque located in the upper part of the Val Vallaccia, near Livigno, in the Italian Central Alps. The La Foppa cirque is characterized by five rock glaciers, of which four are active and one is of uncertain activity or is inactive. These rock glaciers, especially the two largest, named La Foppa I and La Foppa II, have been the subject of geophysical investigations (Lozej and Guglielmin, 1992; Guglielmin et al., 1994; Guglielmin 1997) including BTS measurements (bottom temperature of snow; more than 70 measurements between 1990 and 1993) and STG measurements (shallow temperature of ground in summer) (Calderoni et al. 1993; Guglielmin and Tellini 1992, 1994; Guglielmin 1997). The distribution of BTS and STG measurements indicate that above 2800 asl the permafrost is continuous whereas below this elevation it is constrained inside the rock glaciers, where it is not continuous.
Three boreholes have been established. One is in the frontal part of La Foppa I where the BTS values are always lower than -3 degrees C, and where the active layer detected with vertical electrical soundings (V.E.S.) ranges from 0.8 to 2.7 meters. The second borehole is in the central part of La Foppa I, where the BTS values range between -0.5 and -2.1 degrees C, and the V.E.S. indicate an active layer of 3 - 5.5 meters thick. The third borehole is located on the moraine ridge (of Late Glacial age) at 10 meters of the lateral slope of La Foppa I that overlaps the moraine ridge. Here the BTS values and V.E.S. point out the absence of permafrost. Near the third borehole there is a meteorological station that measures air temperature at 4 meters above the ground, snow cover, snow temperature every 20 cm up to 420 cm, precipitation, wind speed and direction, atmospheric pressure, relative humidity, and soil temperature at 2 and 30 cm depth. Borehole data are recorded on data loggers. A sample of the data is presented on the CAPS Version 1.0 CD-ROM. In this data file, data values must be divided by 10 to obtain the correct value.
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