Volcanic lake systematics I. Physical constraints

Abstract

Volcanic lakes have a wide range of characteristics, and we make an attempt to delineate the limiting physical conditions for several lake classes. The ratio between heat input and heat dissipation capacity of a lake constrains the temperature for perfectly mixed steady-state volcanic lakes. Poorly mixed lakes are also conditioned by this ratio, but their temperature structure is also strongly influenced by the hydrodynamics resulting from different mechanisms of heat transfer. The steady-state temperatures of volcanic lakes are largely determined by the magnitude of the volcanic heat influx relative to the surface area of the lake. Small lakes have only a small capacity for heat dissipation and their temperature rises quickly with only small heat inputs; large lakes are buffered against variations in heat input. Both the heat dissipation and meteoric water input into a lake are functions of lake surface area and therefore each lake water temperature demands a certain precipitation rate for mass conservation, independent of lake size. The results of energy/ mass-balance modeling shows that under common atmospheric conditions, most steady-state volcanic lakes are unlikely to maintain a temperature in excess of 45-50 7C. Validation of the volcanic lake model was performed using published data from Yugama Lake (Japan) and the Keli Mutu lakes (Indonesia). Also, the model was applied to 24 natural systems to provide a baseline assessment of energy fluxes under the model assumptions so future work on those systems can identify nuances in individual systems that deviate from the simple model conditions. We recommend the model for use in assessing temperature variations and volcanic lake stability in settings with known physical and atmospheric conditions. Application of the energy/mass balance calculations of model lakes provides a genetic classification scheme largely based on physical process parameters.

An oligarchic microbial assemblage in the anoxic bottom waters of a volcanic subglacial lake

“…Subglacial volcanic lakes differ markedly from their subaerial counterparts; the former are diluted by melting glacial ice while the latter experience evaporation and sunlight (Pasternack and Varekamp, 1997). The Grímsvö tn lake is a cold (À0.2 1C), oligotrophic (B0.3 mg l À1 particulate organic carbon), acidic (pH 5.7-7.0) and fresh (total dissolved solids ¼ 200 mg l À1 ) body of water with little apparent geothermal influence (Á gú stsdó ttir and Brantley, 1994; Gaidos et al, 2004).…”

Survey and assessment of post volcanic activities of a young caldera lake, Lake Cuicocha, Ecuador

“…Thus, different volcanic lake types are formed, and have been classified by their water physico-chemical constraints by Pasternack and Varekamp (1997). These authors distinguished volcanic lakes with different levels of activity, namely cool to hot acid-brine lakes, reduced to oxidized acid-saline lakes, acid-sulphate lakes and bursting to buoyant plume bicarbonate lakes; only neutral dilute volcanic lakes do not show any activity.…”

Volcanic heat flux and short‐term holomixis during the summer stratification period in a crater lake

“…The volcanic heat supply of crater lakes also affects thermal stratification (McManus et al 1993;Takano et al 1994;Crawford and Collier 1997). In some crater lakes, lake water temperature exceeds ambient temperature because of the large geothermal heat flux from the lake bottom, and the heat flux may change in accordance with volcanic activity (Brown et al 1989;Rowe et al 1992;Ohba et al 1994;Pasternack and Varekamp 1997).…”

“…Although Crater Lake, the deepest lake in the United States, tends to have incomplete deep-water ventilation, a small flux of hydrothermal heat (0.9-1.2 W m Ϫ2 ) produces instabilities in the density structure that may drive deep-lake mixing (McManus et al 1993). Pasternack and Varekamp (1997) pointed out that the steady-state temperatures of perfectly mixed crater lakes are determined mainly by the magnitude of the volcanic heat influx relative to the lake surface area. Lake Yugama in Japan, which receives a hydrothermal heat flux of 3-10 MW, had water temperatures 9ЊC higher than ambient air temperatures over the entire period from 1988 to 1989.…”

“…To estimate the major factors driving the decrease in epilimnetic temperature, we estimated the heat flux of epilimnetic water on the onset days of short-term holomictic events and 2 d before mixing by using a box model (Rowe et al 1992;Ohba et al 1994;Pasternack and Varekamp 1997). The heat budget of the epilimnion during the stratification period is given by E epil ϭ E rad ϩ E rain ϩ E evap ϩ E cond ϩ E sun ϩ E vol where E epil is the rate of change in the heat energy of the epilimnion, and E rad , E rain , E evap , E cond , E sun , and E vol are the radiative heat flux, the heat inflow due to rain water, the evaporative heat loss, the conductive heat flux, the solar heat influx, and the volcanic heat inflow from the bottom under the epilimnion, respectively.…”