南硫黄島は伊豆小笠原弧南端部に位置する無人の火山島である．島は直径約2 kmしかないにも関わらず，山頂標高は916 mもあり，伊豆小笠原諸島のなかでは最高峰である．このため急峻な円錐状をしており，海岸沿いまで海食崖が迫っている．

 火山地質的には溶岩やアグルチネートを主体とした成層火山であり，ソレアイト質玄武岩とアルカリ玄武岩の中間的な組成を示す．歴史噴火の記録はないが，福山（1983）は溶岩流や岩脈の熱残留磁化方位が正であることから，本火山の活動時期は古くとも数十万年とした．また未公表ではあるが，玄武岩から約3万年前のK-Ar年代も報告されている（Nakano et al., 2009）．

 南硫黄島は，北福徳カルデラと呼ばれる，伊豆小笠原弧最大級の海底カルデラ（16×10 km）の南縁上に位置しており，海底地形の特徴から，南北に約50 km，東西に約25 kmもある巨大海底複合火山の一部であることが最近報告された（Minami and Tani, 2023）．2021年8月に噴火した福徳岡ノ場も北福徳カルデラ内の後カルデラ火山である．

 本写真は東北海洋生態系調査研究船「新青丸」を用いて実施した，福徳岡ノ場火山2021年噴火の緊急調査航海にて撮影したものである．

（写真・解説：谷　健一郎　2022年8月29日撮影）

 Nitrogen occurs abundantly in the Earth's atmosphere in the form of nitrogen molecules. However, nitrogen molecules are stable and few organisms can utilize them directly. Nevertheless, through the artificial production of nitrogen compounds and exhaust gases from production facilities and motor vehicles, large amounts of nitrogen compounds are deposited in forest ecosystems, causing various problems. The responses of forests to deposited nitrogen differ depending on the environment. Those responses are summarized by region (Europe and the US, and Asia (Japan and China)) from previous studies. 1) While indicators of nitrogen saturation are valid in Europe and the United States, attention should be paid to hydrological conditions and other factors when applying them to Japan and other regions. 2) In recent years, high NO₃⁻ concentrations have been observed at forested watersheds in Japan due to air pollution near large cities and transboundary air pollution. 3) Significantly high NO₃⁻ concentrations have been observed at forested watersheds in China due to nitrogen deposition. 4) Nitrogen loading from rocks is not negligible in some areas. 5) New insights are being obtained into the functions of microbes involved in the nitrogen cycle in soil.

 A notable swarm activity occurred at the northern shore of Lake Ashi in May 2015. During the activity, a rapid diffusion of the active area was observed with a diffusion coefficient estimated at about 16 m²/sec. The swarm activity occurred during an active period of Hakone volcano while dilatation of the edifice had been continuing. The swarm activity was not correlated with seismic activity under the central cones of Hakone volcano and there was a spatial gap between the two areas of seismic activity. A tilt meter at Kojiri, located at the northern border of the swarm area, had been showing a gradual northward inclination of the ground since the end of April. The swarm activity began with shallow earthquakes at the northwestern side of the swarm area on May 8. Subsequently, the active area moved gradually eastward. Many shallow earthquakes occurred near Kojiri during the morning of May 15; then, at around midday, the active area expanded rapidly. The earthquakes at the time of the rapid diffusion were centered at depths of about 2 km. Based on these observations the following hypothesis is proposed as the cause of the 2015 Hakone swarm activity. When Hakone volcano was activated in April 2015, volcanic fluids containing a large volume of gas began to enter a fracture zone that extended northwest at a depth of about 2 km under a cap rock layer. On May 8, volcanic fluids ascended under pressure at the northwest side of the zone near the western caldera limb that was not covered by the cap rock. When the fluids came into contact with the atmosphere, dissolved gas was released and entered cracks in the rock. The increase of gas pore pressure in the cracks made them slip easily and shallow earthquakes occurred. The influence of the pressure decrease in the fluid propagated slowly through the fluid conduit. On May 14 or the morning of May 15, it reached a reservoir of high-pressure fluids that had been formed near the Kojiri tiltmeter station. Around midday on May 15 fluids in the reservoir, with the increase of hydro-pressure, ascended into the cap rock through cracks, and made contact with the atmosphere. At that time, the pressure in the reservoir decreased suddenly and a large volume of volcanic gases dissolved in the fluids was released, causing violent seismic activity. The influence of the abrupt decrease of pressure in the reservoir propagated rapidly along the fluid conduit located at a depth of around 2 km, bringing about a rapid increase in the area of earthquake occurrence.

 Two previously described tephras are correlated with tephra layers at several areas in the Kanto Plain, including the Sayama Hills, beneath the Musashino Uplands and the Tama Hills in western part of the plain, the Choshi district, the Boso Peninsula, and the northern part of the Miura Peninsula, defining them as SYG-Kd29 and Ob3-Kd31B. The eruption ages for SYG-Kd29 and Ob3-Kd31B are precisely determined from a chronological framework composed of biostratigraphy, magneto-stratigraphy, and oxygen isotope stratigraphy, with estimations of 1.634 Ma (around the peak of MIS 57) and 1.664 Ma (transition from MIS 59 to 58), respectively. Major and minor elemental compositions of volcanic glass shards suggest the source volcano of SYG-Kd29 is located in the northern Honshu to Hokkaido area. On the other hand, major elemental compositions of volcanic glass shards in Ob3-Kd31B suggest that its source is located in the central Japanese Islands or the Izu-Bonin Arc. The paleogeography of the southern part of the Kanto Plain around the deposit of SYG-Kd29 is as follows: alternating shallow marine and fluvial environments caused by glacial eustasy in and around the westernmost part of the Musashino Uplands and the Sayama Hills, oceanic and bathyal environment in the central part of the Tama Hills and the northern part of the Miura Peninsula with a depth of > 200 m, and abyssal environment from the Choshi district to the Boso Peninsula with a depth of > 1,500 m.

 Ceurrent trends in non-agricultural work are the subject of a case study on a village of the Bai people in Heqing County, Yunnan Province, China. Non-agricultural work has continued since the late Qing dynasty with non-agricultural work in the construction industry, including carpentry, thriving. Prior to the Republic of China, local construction was carried out from within the county and the neighboring county of Lijiang. The impetus for change was government recruitment of road construction workers in Zhongdian (Gyalthang) in 1957. In 1970, the village began to receive frequent requests for construction work within Zhongdian. Since the initiation of economic reforms in China, villagers have continued to build in their hometowns of Heqing County, Lijiang, and Diqing Tibetan autonomous prefecture, including Zhongdian. According to two surveys of all households conducted in 2007 and 2021, the construction industry has been affected by the economic situation. Although there has been a slight decrease in construction demand, the construction industry, including carpenters, continues to prosper even today. After the economic reforms in China, non-agricultural work using skills spread from carpentry to silver handcrafts and automobile repairs. A 2021 survey found a small number of villagers working in factories in Taizhou, Zhejiang. The background to this is a rapid spread of small electric trucks from around 2014. As a result, non-agricultural work without skills in villages, such as driving agricultural trucks has almost disappeared. Following the diffusion of small electric trucks among households, demand in the village for transportation using agricultural trucks disappeared. Residents engaging in non-agricultural work using agricultural trucks did not have skills, so they chose factory work in coastal areas where wages were relatively high. Non-agricultural work using skills was traditionally considered necessary for villagers to survive in China's outlying regions.

 Some outstanding issues noted by Matsuyama (2023) are clarified regarding: (1) digitization of precipitation data at the Oki-mura Water Supply Branch of Ogasawara Village, Haha-jima, Ogasawara (Bonin) Islands before 1978; and, (2) accuracy of 10-day accumulated precipitation data reported by Maejima and Oka (1980). The key findings are as follows: (1) Precipitation data at the Oki-mura Water Supply Branch were digitized from rain gauge charts dating from September 21, 1973 to December 31, 1977. These records were then aligned with daily precipitation data from 1978 to 2022. (2) Of the 153 10-day accumulated precipitation data tabulated by Maejima and Oka (1980) at the Oki-mura Water Supply Branch from May 1974 to July 1978, 128 were regarded as probable estimates. Comparing data produced in (1), we found that the discrepancy is within ±0.5 mm for 113 data. Hence, we concluded that data regarded to be probable estimates may be used for analyzing monthly and/or long-term variations, although the reason for probable estimates remains unclear. Matsuyama (2023) reported a statistically significant decreasing trend at the 5% level in February's monthly precipitation at Haha-jima from 1978 to 2020. However, this trend is not observed from 1973 to 2022. From 1973 to 2022, monthly precipitation in September and October at both Haha-jima and Chichi-jima shows a statistically significant increasing trend at the 5% level.