Posteruption chemical evolution of a volcanic caldera lake: Karymsky Lake, Kamchatka

The 1996 short‐lived subaqueous eruption at the Karymsky caldera lake suddenly changed the composition of the lake water. The lake, with a surface area of ~10 km 2 and a volume of ~0.5 km 3 , became acidic, increased its salinity to ~1000 mg/kg, and became dominated by SO 4 2− and Ca 2+ . Since the eruption, the lake chemistry has evolved in a predictable manner described by simple box model. As a result of dilution by incoming SO 4 ‐Ca‐Mg‐poor water, SO 4 , Ca, and Mg concentrations follow a simple exponential decrease with a characteristic time close to the residence time of the lake. Na, K, and Cl decrease relatively significantly slower, indicating a continuing input of these constituents into the lake that was initiated during the eruption. Thus, the dynamics of two groups of lake water solutes can be predicted by a simple box model for water and solute mass balance.