Geological, geophysical, and geochemical constraints on the time-space evolution of Akan composite caldera, Hokkaido, Japan

Abstract

The case study of Akan caldera shows a possible time-space evolutionary pathway for a caldera complex where several smaller calderas are nested. KEYWORDS composite caldera, lithic fragments, Bouguer anomaly map, magma system, Akan volcano 2 Geological background General geology around Akan volcanoAkan volcano is located on the south end of the Akan-Shiretoko volcanic chain (ASVC) in the southern Kurile arc (Figures 1A,B). This part of the arc is characterized by oblique subduction of the Pacific Plate beneath the North American Plate, which began during the late Miocene (Kimura, 1986).

Varying stages of ecological succession in lakes subdivided by volcanic eruptions at Akan Caldera, Japan

“…Akan Caldera is situated at the southern end of the Akan-Shiretoko Volcanic Chain, a volcanic region in eastern Hokkaido, Japan (Hasegawa & Nakagawa, 2016;Hasegawa et al, 2022). The outer shape of the caldera is oblong (24 km east-west × 13 km north-south) and a central cone, i.e., Mt.…”

“…Oligo-meso-eutrophic and dystrophic occurrence types are distributed in eutrophic and dystrophic lakes, respectively. L lake, P pond nonuniform (Satoh, 1965;Maeda Ippoen Foundation, 1994;Hasegawa et al, 2022); thus, further studies are needed to determine the actual phosphorus loading from the watersheds. Such studies will provide a clearer picture of the diversification of trophic statuses in the Akan Caldera lakes, including the abovementioned lake-specific events.…”

Stratigraphy and eruptive history of Gedemsa caldera volcano, Central Main Ethiopian Rift

“…Lipman et al, 1984;Branney, 1995). Some calderas are geometrically complex suggesting more than one formation process and multiple structural types (Cole et al, 1998;Lipman, 2000;Acocella, 2006Acocella, , 2007Geyer and Marti, 2014;Hasegawa et al, 2022). In some cases, multiple subsequent eruption episodes that gave rise to caldera formation are related to the evacuation of multiple magma reservoirs (e.g.…”