Increased rates of large‐magnitude explosive eruptions in Japan in the late Neogene and Quaternary

Abstract

Tephra layers in marine sediment cores from scientific ocean drilling largely record high‐magnitude silicic explosive eruptions in the Japan arc for up to the last 20 million years. Analysis of the thickness variation with distance of 180 tephra layers from a global data set suggests that the majority of the visible tephra layers used in this study are the products of caldera‐forming eruptions with magnitude (M) > 6, considering their distances at the respective drilling sites to their likely volcanic sources. Frequency of visible tephra layers in cores indicates a marked increase in rates of large magnitude explosive eruptions at ∼8 Ma, 6–4 Ma, and further increase after ∼2 Ma. These changes are attributed to major changes in tectonic plate interactions. Lower rates of large magnitude explosive volcanism in the Miocene are related to a strike‐slip‐dominated boundary (and temporary cessation or deceleration of subduction) between the Philippine Sea Plate and southwest Japan, combined with the possibility that much of the arc in northern Japan was submerged beneath sea level partly due to previous tectonic extension of northern Honshu related to formation of the Sea of Japan. Changes in plate motions and subduction dynamics during the ∼8 Ma to present period led to (1) increased arc‐normal subduction in southwest Japan (and resumption of arc volcanism) and (2) shift from extension to compression of the upper plate in northeast Japan, leading to uplift, crustal thickening and favorable conditions for accumulation of the large volumes of silicic magma needed for explosive caldera‐forming eruptions.

Miocene to Holocene Marine Tephrostratigraphy Offshore Northern Central America and Southern Mexico: Pulsed Activity of Known Volcanic Complexes

“…The same pulses were also recognized in a tephra compilation from several DSDP sites and especially in Legs 66 and 67 (Cadet, Pouclet, et al, ; Cadet, Thisse, et al, ; Kennett et al, ; Kennett & Thunell, ). Marine tephra records from Japan indicate similar periods of increased explosive volcanic activity between 2–0, 6–4, ~8, and possibly 15–13 Ma (Mahony et al, ; Figure ). In the Caribbean, Carey and Sigurdsson () and Sigurdsson et al () studied the temporal distribution of ash beds at several ODP sites.…”

Why No Porphyry Copper Deposits in Japan and South Korea?

“…b). The submarine record shows increased intensity of caldera eruptions in NE and SW Japan at 8, 4–6, and 2 Ma (Mahony et al , ). Crustal extension linked to slab rollback from ~2 Ma promoted the enhanced caldera development in SW Japan (Mahony et al , ): a mechanism that may well have been responsible for the Cretaceous and Paleogene caldera‐forming events (e.g., Imaoka et al , ; Kim et al , ; see above) as well as for major caldera flare‐ups elsewhere (Best et al , ).…”

Magmatic Landscape Construction

“…A preliminary planform area compilation comes from the global volume database on large explosive eruptions (LaMEVE; Brown et al, , Figure d). We use primary data compiled by Mahoney et al (), which include the maximum area and thickness in the near‐vent region of each eruption. Because these data do not include eruptions smaller than those for which the eruption catalog is demonstrably statistically incomplete, we supplement LaMEVE with a compilation from the primary literature (supporting information) that includes eruptions from Hawaii, Iceland, Mount St. Helens, and New Zealand.…”