An extremely large magnitude eruption close to the Plio-Pleistocene boundary: reconstruction of eruptive style and history of the Ebisutoge-Fukuda tephra, central Japan

Citation
K. Kataoka et al., An extremely large magnitude eruption close to the Plio-Pleistocene boundary: reconstruction of eruptive style and history of the Ebisutoge-Fukuda tephra, central Japan, J VOLCANOL, 107(1-3), 2001, pp. 47-69
Citations number
50
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH
ISSN journal
0377-0273 → ACNP
Volume
107
Issue
1-3
Year of publication
2001
Pages
47 - 69
Database
ISI
SICI code
0377-0273(200106)107:1-3<47:AELMEC>2.0.ZU;2-S
Abstract
An extremely large magnitude eruption of the Ebisutoge-Fukuda tephra, close to the Plio-Pleistocene boundary, central Japan. spread volcanic materials widely more than 290,000 km(2) reaching more than 300 km from the probable source. Characteristics of the distal air-fall ash (> 150 km away from the vent) and proximal pyroclastic deposits are clarified to constrain the eru ptive style, history, and magnitude of the Ebisutoge-Fukuda eruption. Eruptive history had five phases. Phase 1 is phreatoplinian eruption produc ing > 105 km(3) of volcanic materials. Phases 2 and 3 are plinian eruption and transition to pyroclastic how. Plinian activity also occurred in phase 3, which ejected conspicuous obsidian fragments to the distal locations. In phase 5, collapse of eruption column triggered by phase 4. generated large pyroclastic how in all directions and resulted in more than 250-350 km(3) of deposits. Thus, the total volume of this tephra amounts over 380-390 km( 3). This indicates that the Volcanic Explosivity Index (VEI) of the Ebisuto ge-Fukuda tephra is greater than 7. The huge thickness of reworked volcanic lastic deposits overlying the fall units also attests to the tremendous vol ume of eruptive materials of this tephra. Numerous ancient tephra layers with large volume have been reported worldwi de, but sources and eruptive history are often unknown and difficult to det ermine. Comparison of distal air-fall ashes with proximal pyroclastic depos its revealed eruption style, history and magnitude of the Ebisutoge-Fukuda tephra. Hence, recognition of the Ebisutoge-Fukuda tephra, is useful for un derstanding the volcanic activity during the Pliocene to Pleistocene, is im portant as a boundary marker bed, and can be used to interpret the global e nvironmental and climatic impact of large magnitude eruptions in the past. (C) 2001 Elsevier Science B.V, All rights reserved.