CLUSTERS OF SMALL MONOGENETIC CONES: A PARTICULAR TYPE OF CONFINED VOLCANISM

Monogenetic volcanoes are a frequent type of volcanisms on Earth. They are frequently paired with polygenetic ones. We can distinguish them by their place of origin. If a new vent opens on or near an existing volcano, it will join with a main crater of the volcano, or form a parasite on a flank of the volcano. If the vent opens at a certain distance from an existing volcano, its activities are independent of that volcano and its magma sources are also separate. At present we have difficulty in distinguishing between monogenetic and polygenetic volcanoes, when we do not know the formers' history of eruptions. We are sure that Jorullo and Paricutin, both born before our eyes, are important and indispensable examples for discussion on monogenetic volcanism. The present discussion starts fundamentally from the knowledge of these two volcanoes. Among examples of monogenetic cones, we find clusters of monogenetic cones much smaller than Jorullo and Paricutin in volume, and densely distributed in a certain area of the world. The present paper discusses the three areas in the Far East. Morphological characteristics of the three areas show a strong volume contrast between component cones of the cluster areas and the twins of Jorullo and Paricutin. Averaged component volume of the former is approximately equal to 1/10 (2 )times as large as that of the latter. The present author tentatively presents qualitative interpretation of the above quantitative characteristics, mainly from a geophysical standpoint.