This case study deals with a rock face monitoring in urban areas using a Terrestrial Laser Scanner. The pilot study area is an almost vertical, fifty meter high cliff, on top of which the village of Castellfollit de la Roca is located. Rockfall activity is currently causing a retreat of the rock face, which may endanger the houses located at its edge. TLS datasets consist of high density 3-D point clouds acquired from five stations, nine times in a time span of 22 months (from March 2006 to January 2008). The change detection, i.e. rockfalls, was performed through a sequential comparison of datasets. Two types of mass movement were detected in the monitoring period: (a) detachment of single basaltic columns, with magnitudes below 1.5 m<sup>3</sup> and (b) detachment of groups of columns, with magnitudes of 1.5 to 150 m<sup>3</sup>. Furthermore, the historical record revealed (c) the occurrence of slab failures with magnitudes higher than 150 m<sup>3</sup>. Displacements of a likely slab failure were measured, suggesting an apparent stationary stage. Even failures are clearly episodic, our results, together with the study of the historical record, enabled us to estimate a mean detachment of material from 46 to 91.5 m<sup>3</sup> year<sup>−1</sup>. The application of TLS considerably improved our understanding of rockfall phenomena in the study area
Johnsons and Hurd Glaciers are the two main glacier units of Hurd Peninsula ice cap, Livingston Island, South Shetland Islands, Antarctica. They presently cover an area of about 10 km 2 . Johnsons is a tidewater glacier, while Hurd Glacier ends on emerged land. In this paper, we estimate the changes in ice volume during the period 1956-2000, and compare them with the regional meteorological records. The volume-change estimates are based on the comparison of digital terrain models for the glacier surface, constructed from aerial photographs taken by the British Antarctic Survey in 1956 and from our geodetic measurements in 1999/2000. The total volume estimates are based on an ice-thickness map constructed from radio-echo sounding profiles (18-25 MHz) done in 1999-2001, showing maximum ice thickness of about 200 m. We estimate the changes in ice volume during the period 1956-2000 to be -0.108 AE AE 0.048 km 3 , which represents a 10.0 AE 4.5% % decrease from the 1956 total volume of 1.076 AE 0.055 km 3 and is equivalent to an average annual mass balance of -0.23 AE 0.10 m w.e. during 1956-2000. Ice-thickness changes range from -40 to þ20 m, averaging -5.5 AE 4.4 m. Most areas show ice thinning; the thickening is limited to a small area within Johnsons Glacier. All glacier fronts, except Johnsons' calving front, show retreat. These changes are consistent with the regional meteorological records for mean summer temperature, which show a trend of þ0.023 AE 0.0058C a -1 during the period 1956-2000.
Tephra layers are interstratified in the ice caps of the South Shetland Islands. Although previously poorly investigated, they are potential targets for the application of tephrochronology and, hence, may provide temporal constraints on glaciological models for the region. Several tephra layers crop out in the coastal ice-cliffs and ablation ramps of Livingston Island. Using stratigraphical position, granulometry and bulk sample geochemistry, the tephra layers can be divided into three groups (TPH1, TPH2 and TPH3, from top to base). The source for all of the tephras is unequivocally identified as Deception Island, a large active volcano in Bransfield Strait, situated about 35 km south of Livingston Island. TPH1 (a single layer) is strongly correlated compositionally with tephra erupted in 1970 from centres close to Telefon Bay. This is the first time it has been possible to correlate a distal tephra with a pyroclastic unit in the source volcano in the Antarctic Peninsula region. TPH2 (usually two layers, sometimes only one) was probably erupted from a tuff cone centre within the Crater Lake cluster of vents. From historical accounts, it is deduced that the numerous co-eruptive Crater Lake vents were active prior to 1829 and, from their relatively fresh appearance, an eighteen-century age for the eruptions is possible. TPH3 comprises at least four discrete tephra layers with a much wider compositional range than either TPH1 or TPH2. It may have been erupted during successive months or years. Compositional comparisons of TPH3 with possible source vents on Deception Island are ambiguous, but there is a reasonably good similarity with tephras erupted at Wensleydale Beacon and/or Vapour Col. However, it is also conceivable that the source(s) for TPH3 are no longer preserved on Deception Island. The age of the TPH3 eruptions is unknown but it must be prior to 1829 and is unlikely to be more than a few centuries.
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