کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4690265 | 1636135 | 2009 | 18 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
A 90,000-year tephrostratigraphic framework of Aso Volcano, Japan
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
A detailed 90,000-year tephrostratigraphic framework of Aso Volcano, southwestern Japan, has been constructed to understand the post-caldera eruptive history of the volcano. Post-caldera central cones were initiated soon after the last caldera-forming pyroclastic-flow eruption (90Â ka), and have produced voluminous tephra and lava flows. The tephrostratigraphic sequence preserved above the caldera-forming stage deposits reaches a total thickness of 100Â m near the eastern caldera rim. The sequence is composed mainly of mafic scoria-fall and ash-fall deposits but 36 silicic pumice-fall deposits are very useful key beds for correlation of the stratigraphic sequence. Explosive, silicic pumice-fall deposits that fell far beyond the caldera have occurred at intervals of about 2500Â years in the post-caldera activity. Three pumice-fall deposits could be correlated with lava flows or an edifice in the western part of the central cones, although the other silicic tephra beds were erupted at unknown vents, which are probably buried by the younger products from the present central cones. Most of silicic eruptions produced deposits smaller than 0.1Â km3, but bulk volumes of two silicic eruptions producing the Nojiri pumice (84Â ka) and Kusasenrigahama pumice (Kpfa; 30Â ka) were on the order of 1Â km3 (VEI 5). The largest pyroclastic eruption occurred at the Kusasenrigahama crater about 30Â ka. This catastrophic eruption began with a dacitic lava flow and thereafter produced Kpfa (2.2Â km3). Total tephra volume in the past 90,000Â years is estimated at about 18.1Â km3 (dense rock equivalent: DRE), whereas total volume for edifices of the post-caldera central cones is calculated at about 112Â km3, which is six times greater than the former. Therefore, the average magma discharge rate during the post-caldera stage of Aso Volcano is estimated at about 1.5Â km3/ky, which is similar to the rates of other Quaternary volcanoes in Japan.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Sedimentary Geology - Volume 220, Issues 3â4, 15 October 2009, Pages 169-189
Journal: Sedimentary Geology - Volume 220, Issues 3â4, 15 October 2009, Pages 169-189
نویسندگان
Yasuo Miyabuchi,