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Rishirizan is a highly dissected andesitic stratovolcano that forms a 20-km-wide island west of the northern tip of Hokkaido. Extensive erosion has produced an extremely rugged topography, with a dramatic sharp-topped, 1719-m-high summit flanked by steep-sided radial ridges. A stratovolcano and flank lava domes were constructed beginning less than 200,000 years ago. Eruptions at the stratovolcano ceased about 37,000 years ago, after which only flank vents were active. Late-stage eruptions took place from scoria cones and maars along a 15-km-long NW-SE trend that extends to the SE coast. Flank eruptions were dominantly basaltic, but also included andesitic and rhyolitic activity. Extensive late-stage lava flows during the late Pleistocene form much of the northern and western coasts and extend offshore. The latest eruptions took place a few thousand years ago.
Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).
|Start Date||Stop Date||Eruption Certainty||VEI||Evidence||Activity Area or Unit|
|5830 BCE ± 300 years||Unknown||Confirmed||Radiocarbon (uncorrected)||Rs-Ho tephra|
This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.
|Risiri | Rishiri|
|Rishiri is a highly dissected andesitic stratovolcano that forms an island west of the northern tip of Hokkaido. The main edifice ceased erupting during the Pleistocene, and extensive erosion has created a rugged dissected summit flanked by radial knife-edged ridges. Scoria cones and maars on the lower flanks have been active during the late Pleistocene and early Holocene.
Photo by Yoshihiro Ishizuka, 1997 (Hokkaido University).
|Rishiri volcano is a highly dissected stratovolcano that forms an island off the NW tip of Hokkaido. The composite cone (center) and flank scoria cones (middle ground) are mirrored on the surface of a maar on the lower south flank. The stratovolcano was constructed during the Pleistocene. Scoria cones and maars on the lower flanks erupted 30,000-8,000 years ago.
Photo by Yoshihiro Ishizuka, 1993 (Hokkaido University).
The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.
IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..
Ishizuka Y, 1999. Eruptive history of Rishiri volcano, northern Hokkaido, Japan. Bull Volc Soc Japan (Kazan), 44: 23-40 (in Japanese with English abs).
Japan Meteorological Agency, 2013. National Catalogue of the Active Volcanoes in Japan (fourth edition, English version). Japan Meteorological Agency.
Kuritani T, Yoshida T, Nagahashi Y, 2010. Internal differentiation of Kutsugata lava flow from Rishiri Volcano, Japan: Processes and timescales of segregation structures' formation. J Volc Geotherm Res, 195: 57-68.
Machida H, 1976. Stratigraphy and chronology of late Quaternary marker-tephras in Japan. Tokyo Metropolitan Univ Geog Rpt, 11: 109-132.
Nakano S, Yamamoto T, Iwaya T, Itoh J, Takada A, 2001-. Quaternary Volcanoes of Japan. Geol Surv Japan, AIST, http://www.aist.go.jp/RIODB/strata/VOL_JP/.