Rockslides on the Terminus of“Jökulsárgilsjökull”, Southern Iceland
作者:
SigurđssonOddur,
WilliamsRichard S.,
期刊:
Geografiska Annaler: Series A, Physical Geography
(Taylor Available online 1991)
卷期:
Volume 73,
issue 3-4
页码: 129-140
ISSN:0435-3676
年代: 1991
DOI:10.1080/04353676.1991.11880338
出版商: Taylor&Francis
数据来源: Taylor
摘要:
ABSTRACTOn 10 November 1976, a 1.5 km×0.5 km rockslide deposit on the surface of an unnamed outlet glacier of Mýrdalsjökull ice cap, southern Iceland, was observed from an aircraft. Deposits from two different rockslides, including the larger one observed on 10 November 1976, were visible on a 10 September 1978 aerial photograph of the unnamed outlet glacier. An analysis of vertical and oblique aerial photographs, Landsat images, and seismological records was used to establish the time of occurrence of the larger rockslide to a 30-day period between 9 September 1972 and 9 October 1972. The trigger mechanisms for the rockslide activity appear to have been heavy precipitation prior to the event and the decrease of buttressing mass at the base of the valley wall resulting from recession of the glacier (decrease in width and thickness). The recession led to instability of highly altered hyaloclastite bedrock, talus, and morainal materials on an oversteepened slope. An earthquake as a trigger mechanism was considered to be unlikely from a thorough review of seismic records. Measurements of the downglacier movement of the larger rockslide deposit give an average speed of the glacier as 30±3 m a-1between September/October 1972 and 10 September 1978. From measurements of aerial photographs taken on 10 September 1978 and 4 September 1984, the average speed of the glacier increased to 45 m a-1during this 6-year interval. Although the terminus of the unnamed outlet glacier had not yet begun to advance in 1986, it had undergone thickening since 1978.
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