Yanagimachi (1983) clarified that the older and younger glacial landforms in the northern part of the Kiso Mountain Range were formed during the Nakagoshodani Stadial I (ca. 80, 000_??_45, 000 years B. P.) and Nakagoshodani Stadial III (ca. 30, 000_??_10, 000 years B. P.), respectively. Nakagoshodani Stadial I is characterized by the largest extension of glaciers. The purpose of present paper is to reconstruct the vertical distribution of morphogenetic and vegetation zones at each maximal phase of glaciation (i.e. 50, 000 years B. P. and 20, 000 years B.P.) in this region, by considering mainly equilibrium-line (orographic snowline) as well as forest-line. Equilibrium-line altitude (ELA) and forest-line altitude (FLA) in the vicinity of Mt. Kisokomagatake (2, 956 m a. s. l.) are 4, 000 m a. s. 1. and 2, 600 m a. s. 1. respectively. The ELA and FLA of 50, 000 years B. P. were lowered about 1, 600 m and 400 m below the present levels, respectively. On the other hand, the lowering of them at 20, 000 years B. P. were about 1, 400 m and 900 m, respectively. The climatic upper limit of Pinus pumila zone at that time was lowered about 1, 000 m below the present level (3, 200 m a.s. 1.). The vertical changes of morphogenetic and vegetation zones for above-mentioned phases were quite different from each other, as described below: 1. 50, 000 years B. P. (Nakagoshodani Stadial I) The area above the ELA was occupied by nival zone ranging from 500 m to 600 m in height. On the other hand, neither periglacial zone (subnival zone) nor alpine zone were developed above the FLA. Because azonal ice and snow existed even in the area between the ELA and the FLA, both Pinus pumila scrub and periglacial debris fields were sporadically distributed in this area. Valley glaciers were dominant and some of then extended into forest zone (subalpine zone). Besides, ice field was developed southeast of Mt. Kisokomagatake. 2. 20, 000 years B. P. (Nakagoshodani Stadial III) This phase was characterized by both (1) the development of periglacial debris fields and Pinus pumila scrub, and (2) the dominance of cirque and niche type of glaciers. Three zones, i.e., nival, periglacial and alpine zones in descending order, occupied the area above the FLA. Altitudinal ranges of these three zones were estimated to be 400 m, 300 m to 400 m and 500 m to 700 m, respectively, and these zones showed an ideal vertical arrangement. No ice field existed and valley glaciers were much more limited in extension than those of 50, 000 years B. P.. Some of valley glaciers extended only into Pinus, pumila zone (alpine zone) These facts allow the author to deduce the climatic conditions of each phase as follows: the climate of 50, 000 years B. P. was cold and wetter, while that of 20, 000 years B. P. was cold and drier.
A vertical mixing process in a fresh water lake is investigated from the secular variation of tritium concentration in Lake Ikeda. The lake is covering an area of 10.96km2 at an altitude of 66 m whose catchment area is 11. 29km2 and maximum depth is 233m (Fig. 1). A reconnaissance survey was carried out three times, on Oct. 21, 1973, Nov. 5, 1974 and Nov. 30, 1979. Water samples for tritium analysis were collected at every 20m vertically in the center of the lake. Temperature, pH, RpH and electrical conductivity of the water were determined on the spot. On Nov. 25_??_30, 1979 and Nov. 2_??_8, 1980, stream flow measurements and groundwater survey were carried out. The annual water balance of the lake was calculated for the period from 1977 to 1980 (Fig. 2). The mean precipitation to the lake was 2, 295.0mm •yr-1, that is 0.80m3 •sec-1, and the mean evaporation was 1, 018.7mm•yr-1, 0.35m3•sec-l. The evapotranspiration from the catchment area was 712.4mm•yr-1, 0.26m3•sec-1 and the artificial intake was 0.21m3sec-1. The discharge from the lake depends upon groundwater outflow which is about 59% of the total outflow and the seepage is found at Kyoden Spring and the drainage area of Minato River. Secular variation of tritium concentration in lake water is shown in Fig. 7. In 1973 and 1974, the hypolimnion water was in high concentration, but in 1979 the water in uniform. From these facts it seems that the lake water does not mix in every winter but does only in a cold winter which occurs once in several years.