1991 年 30 巻 5 号 p. 391-398
Tephra provide extremely useful sedimentary beds for Quaternary research because they are highly reliable time markers. Tephra studies in Japan have advanced primarily on this basis. Because tephra themselves are products of volcanic eruptions it is quite possible to study explosive eruptions using tephra beds. The thickness of the beds tells us the magnitude of the eruption, while the dispersal pattern of the tephra tells us the intensity of the eruption. The mode of eruption is known by the grain-size characteristics of the tephra deposits. The life history of a volcano can be revealed by alternations of tephra and loess beds.