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The distribution of ash in Icelandic lake sediments and the relative importance of mixing and erosion processes
Author(s) -
Thompson Roy,
Bradshaw Richard H. W.,
Whitley John E.
Publication year - 1986
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/jqs.3390010102
Subject(s) - tephra , geology , volcanic ash , erosion , sediment , silicic , sedimentation , oceanography , geochemistry , holocene , tephrochronology , volcano , pumice , geomorphology
During the Holocene the volcano Hekla explosively emitted highly silicic tephra on four occasions. The ash was widely dispersed by the wind. Distinctive light‐coloured ash layers are now to be seen in the peats of Northern Iceland. Ash from the 1104 AD eruption was carried as far as Scandinavia. The most recent three tephra are preserved in the top 6 m of sediment in Lake Svinavatn. Chemical data from the sediment of Lake Svinavatn, which lies near the north coast of Iceland 170 km from Hekla, reveal the presence of silicic ash above the tephra visible to the naked eye. Unlike the vertical spread of ash in ocean sediment cores which results from biological mixing effects, the upwards spread of ash in the Svinavatn lake sediment cores appears to have been produced by erosion of ash from the lake catchment in the decades following the eruptions. The variations in concentrations of 11 elements, as determined by neutron activation analysis, can be explained by an exponentially decreasing input from catchment erosion. The additional input to each of the three Hekla ash layers was in the region of 3% of the ash which fell on the Svinavatn catchment.