[SVC41-P18] Volcanic sediments distributed around Nakanoyu route, southern foot of Yakedake volcano
Keywords:Volcanic ash, phreatomagmatic eruption, Yakedake
Along the Nakanoyu trail, ten volcanic ash layers (named as YKD-1 to YKD-10 in ascending order) and one massive volcaniclastic deposits (YKD-f1) were observed. Two ash layers (YKD-1 and YKD-2) contain about 20~30% of volcanic glass, indicating that the deposits were derived from magmatic eruption. The radiocarbon age of paleosol intercalated between YKD-1 and YKD-2 is 2339 - 2459 cal BP, suggesting that YKD-2 is correlated with Ykd-TNkb. YKD-1 indicates another magmatic eruption occurred about 2,400 years ago. YKD-10 distributed at the western slope of the Shogaike crater contains smectite and pyrite, suggesting YKD-10 is derived from the 1962-63 eruption according to Ossaka (2003). The radiocarbon age of paleosol immediately below the YKD-f1 is 32 - 74 cal BP. In the early twentieth century, phreatic eruptions repeatedly occurred and lahars were generated to the southern slope of the volcano, probably resulted in YKD-f1 deposits.