Description: From Neal and others (2009): "Bubbling from the Kasatochi crater lake was first reported in the summer of 2005 (McGimsey and others, 2007) and continued into 2006. U.S. Fish and Wildlife Service (USFWS) scientist Brie Drummond, who has spent several summers on the island and was the principal observer of the 2005 activity, visited the south caldera rim on the morning of June 2, 2006. The day was overcast but calm and the lake surface was 'like glass.' Drummond noted a disturbance on the water surface on the west side of the lake, easily visible with the naked eye and very similar to what she had seen in 2005. The disturbance was in the same sector of the lake as in 2005 although perhaps smaller in area [see figs. 52 and 53 in original text].
"She described it as similar to 'rain falling onto a smooth lake surface.' However, in the absence of rain, it probably was a gentle effervescence. The spot on the lake surface was too far from the sheer rock walls to be explained by falling debris disturbing the water, and no birds or other biological activity were observed on the lake to account for the phenomenon.
"Drummond described the bubbling as patchy with variable concentrations of bubbles, some occurring almost in a straight line. The bubbling was rapid and did not appear to change markedly over the course of 30 minutes of observation. As in 2005, Drummond noted no steam, no smell or odd discoloration of the water; gulls floated on the far side of the lake. On a windy day a week prior (May 26, 2006), Drummond’s field party did not see the bubbling, but it may well have been masked by the strong surface wave action due to high winds. Based on Drummond’s sketch, the bubbling zone in 2006 was about 100-200 m (~330-660 ft) across [see figs. 52 and 53 in original text].
"Sampling of lake water was logistically impossible due to difficult, hazardous access, and we have no direct analyses of water or the gas phase to investigate the source of the bubbling. USGS chemist Bill Evans (written commun., 2007) prefers magmatic or hydrothermal processes to explain the bubbling observed in this young volcanic crater lake based on the apparent high flux, the scarcity of vegetation on the crater walls to provide a source for organic decomposition, and the very localized nature of the bubbling areas. The youthfulness of this crater would be consistent with ongoing fumarolic activity that now is submerged. Trains of bubbles rising vertically from subaqueous-gas vents are common at similar volcanic lake settings such as at Mount Spurr and Gas Rocks. The apparent intermittent nature of the bubbling simply may reflect a strong dependence on meteorological conditions favorable to viewing or some seasonal variability depending on water depth. Another possibility put forth by Evans proposes degassing of a volatile-enrich, deeper water layer during disturbance of a salinity-controlled stratified water column."