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Temperature structure and water chemistry of the caldera Lake Öskjuvatn, Iceland 1
Author(s) -
Ólafsson Jón
Publication year - 1980
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1980.25.5.0779
Subject(s) - volcano , caldera , fumarole , geology , sulfate , crater lake , hydrothermal circulation , mineralogy , geochemistry , water column , environmental chemistry , chemistry , oceanography , organic chemistry , seismology
The caldera Lake Öskjuvatn, 217 m in depth, developed after an eruption in 1875. From 1921 to 1926 volcanic eruptions also affected the lake. Deuterium measurements indicate meteoric origin of the water and 6.3% evaporation from the lake. The lake is cold but temperature measurements at one location revealed strong thermal activity at 80‐m depth; in the deepest part of the lake an inverse temperature gradient and static instability were observed, which suggests convective mixing. The concentration of dissolved solids is high and the distribution of major components uniform. High concentrations of silica (110 mg·liter −1 ) and major cations (Na, Ca, K) are indicative of reactions with hot lavas that have flowed into and built up in the lake. A low chloride: sulfate ratio, 0.05 by weight, reflects the relative abundance of sulfur and chlorine in the emanations of the volcano. Dissolved oxygen, pH, manganese, and zinc show variations with depth which may be explained as resulting from emanations of H 2 S and CO 2 from the lake bottom and hydrothermal leaching. Limited biological observations suggest a strongly oligotrophic condition and sparse phyto‐ and zooplankton.