Abstract
In the surrounding area of Rya-zan Volcano (a member of the Zao volcanic group), there are several lakes and swamps, large or small. General survey of these lakes was carried out by KATO, one of the authors. and the results were published in 1961. The present authors carried on limnological study of the lakes in the vicinity of Zao spa with following results. The morphometrical data calculated from the bathymetric maps (Figs. 2-5) are summarized in the next table.
From the hydrochemical point of view, the authors classifies these lakes into the following two groups.
{Group A: Laks Sakazuki-ko, Lake Shiginoyachi-numa
Group B: Lake Dokko-numa, Lake Katakai-numa
The lakes of the former group are distributed at the bottom of Takayu explosion crater, Ryu-zan Volcano. Subjected to the sulfataric action of the volcano, the water is characterized by the high content of sulfate ion. The water of the lakes of the Group B, located between Ryu-zan Volcano and the Zao Proper, is not directly influenced by the activity of the Zao volcanic group.
