Nagoya University · Engineering
Professor Hiroshi Machida's research lab specializes in volcanic and geological sciences, with a primary focus on tephrochronology, volcanic petrology, and the geochemical characterization of Quaternary tephras in Japan. The lab conducts detailed petrographic and refractive index analyses to identify and correlate widespread volcanic ash layers, contributing to regional stratigraphic frameworks and paleoenvironmental reconstructions. Their work also extends to the physical properties of ionic liquids, particularly under extreme conditions, using high-pressure and high-temperature measurements. The integration of field-based tephra studies with laboratory-based analytical techniques defines the lab’s interdisciplinary approach.
Figures are computed from collected data and may differ slightly.
A Holocene volcanic ash layer comprising abundant glass shards occurs as near-surface, soil-forming parent materials in south to north Kyushu and in Shikoku. This layer has been given several local names such as “Akahoya”, “Imogo”, “Onji”, etc. by farmers and pedologists. Its remarkable characteristics as a parent material of soil stimulated the interest of many pedologists to study its source, pedological features, distribution, etc. However, opinions on its source and proper identification var
Pressure−density−temperature (pρT) data for three types of ionic liquid, [emim][lactate], [(C2H4OH)(CH3)3N][lactate], and [bmim][Cl], were measured with a bellows type dilatometer at temperatures up to 452 K and at pressures up to 200 MPa. The Tait equation could correlate the density data as a function of temperature and pressure to within an average relative deviation (ARD) of 0.014 %. The thermal expansion coefficients and the isothermal compressibilities were estimated with the Tait equation
Many widespread Quaternary tephras have been identified in and around Japan. Recent developments in tephra characterization and dating methods have provided a regional stratigraphic framework for Quaternary studies as well as for determining the nature and effects of explosive eruptions. This paper stresses on the importance of tephra catalog compilation and shows a simplified example from Japan.
The Toya pyroclastic flaw deposit is one of the largest tephras of late Pleistocene in northern Japan, covering wide areas of the western part of Hokkaido around the Toya caldera. We have extensively investigated a fine-grained vitric ash layer which has very similar petrographic and chemical properties to the Toya pyroclastic flow deposit at many localities in northern Japan. This ash had already been described and named at several localities in northern Japan by many authors without recognitio
The middle Pleistocene time range is defined here the period before the last interglacial in the Brunhes epoch. In Japan, the Shimosa-Kazusa Groups around the Tokyo Bay in Kanto and the upper part of the Osaka Group in Kinki both represent the standard middle Pleistocene sequences and have been studied in detail. These groups are characterized by the cyclic sedimentation caused by transgression and regression corresponding to climatic changes.The purpose of this paper is to attempt the correlati
The eruptions of the Daisen Valcano (35°22'N, 133°33'E) were mainly rhyodacitic and of the paroxysmal type, producing several extensive sheets of tephra. The Kurayoshi pumice (DKP, for short), one of the excellent Late Pleistocene markers arising from the Daisen valcano, is rhyodacitic in composition with abundant hornblende and orthopyroxene crystals and relatively small amount of biotite. Its identification can be made from the above mentioned mineral assemblages as well as from the characteri
A trachytic tephra fall deposit, the Ulreung-Oki ash, was first discovered at the Torihama archaeological site, in the northern Kinki district, where it forms whitish ash layer in strata bearing artifacts of the earliest Jomon ceramic culture. Occurrence of alkali feldspar and specific amphibole (probably kaersutite) clearly shows that this tephra is alkalic in composition. Correlatives of this tephra have been recognized at many localities in central Honshu and in piston cores from adjacent to
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