Abstract
Reconstruction of the eruption history of an active volcano is necessary to elucidate its volcanic activity and to assess the probability of its volcanic eruption. Yokodake volcano in central Japan is the only active volcano among the Yatsugatake volcano group. It has effused nine lava flows, most of which have not been dated. For this study, we ascertained the eruption ages of the latest lava (Y9) and second most recent lava (Y8) using radiocarbon (14C), thermoluminescence (TL), and paleomagnetic dating methods. Results revealed the eruption ages of the two lava flows and the recent eruption history of Yokodake volcano. Yokodake volcano effused its Y8 lava flow at ca. 3.4 ka, ejected NYk-2 tephra with explosive eruption at ca. 2.4–2.2 ka, and effused the Y9 lava flow associated with Y9-T tephra at ca. 0.6 ka. Magma eruption rates of Yokodake at 34 ky and 3.4 ky were estimated as about 9 × 10−3 km3/ky and 1 × 10−2 km3/ky, indicating a stable eruption rate maintained during the past 34 ky. This result suggests that Yokodake volcano retains some potential for eruption, although the volcanic activity of the Yatsugatake volcanoes (10−1–10−2 km3/ky) has weakened over time.
Highlights
Reconstruction of a volcano’s eruption history is fundamentally important to elucidate its past volcanic activity, and to prepare for future eruptions and to mitigate their damage
Radiocarbon dating The 14C ages of paleosols above Y9-T tephra obtained for samples from localities 1 and 2 were dated as 350 ± 20 yr BP and 510 ± 20 yr BP, which, respectively, correspond to calendar 14C ages of 485–420 and 411–315 cal yr BP (2σ) (535–470 and 461–365 yrb2k) and to 550–510 cal yr BP (2σ) (600–560 yrb2k) (Table 1)
TL dating The equivalent dose was estimated by extrapolation of the linear trend in diagrams of TL growth vs. dose
Summary
Reconstruction of a volcano’s eruption history is fundamentally important to elucidate its past volcanic activity, and to prepare for future eruptions and to mitigate their damage. Understanding the latest activities of an active volcano in terms of their eruption styles, frequencies, and vent locations is important for assessing risks of future volcanic activity. The radiocarbon (14C) dating is frequently used for eruption age determinations of volcanic materials within the past few tens of thousands of years. Paleomagnetism can yield age indications directly from the eruptive materials. The eruption age of lava can be estimated (e.g., Alva-Valdivia et al 2019; Pérez-Rodríguez et al 2019; Risica et al 2019) by comparing the paleosecular variation (PSV) curve with the paleodirection and paleointensity inferred from TRM. Nitta et al Earth, Planets and Space (2020) 72:103 in most cases, paleomagnetic dating needs other dating techniques (Shitaoka et al 2019)
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