Surface displacements and surface age estimates for creeping slope landforms in Northern and Eastern Iceland using digital photogrammetry

摘要

In this study three areas of different active, coarse-debris, slope processes are investigated in Northern and Eastern Iceland. Surface displacement of some glacier-derived rock glaciers and a debris-covered glacier in the Holar area, a moving debris accumulation close to Siglufjoerour and a debris layer in Seyoisfjoerour are measured. The displacement fields are obtained by cross-correlation matching of multi-temporal orthophotos. Orthophotos are generated using a Z/I-Imaging digital photogrammetric workstation and various series of air photos from 1964 to 1994. Cross-correlation matching is done with the CIAS software. The results are analyzed and used for rough surface age estimates. In addition, type and cause of movement are discussed. The velocity of the debris-covered glacier and the rock glaciers in the Holar area averages from 0.14 to 0.67 m a~(-1). The debris accumulation at Almenningsnoef close to Siglufjoerour shows an average displacement of 0.19m a~(-1) with a maximum value of 0.84m a~(-1). The displacements at Almenningsnoef agree well with displacements surveyed by GPS by the Icelandic road authorities. The measured velocities in Seyoisfjoerour, although using air photos taken 30 years apart, turned out not to be significant, but the homogenous direction of the displacement vectors suggests that the debris is currently creeping. Based on the surface age results all the landforms in Holar are suggested to have developed during the late-Holocene cooling period, with ages from around 1500 and 3000 to around 5000 years for the different landforms. These surface age estimates coincide with data from moraine datings nearby and Holocene climatic development in the North Atlantic region.